What are Angiosperms?
Flowering plants
What are gymnosperms
Plants with conical reproduction
Give the Main differences between Monocot and Dicot (eudicot) plants
>Flowing Parts: Monocot- In threes, Dicots - In fours or fives.
>Pollen: Monocot- Monoaperture (one pore), Dicot Triapeture (3 pores).
>Cotyledon: Monocot - One, Dicot: Two.
>Leaf Venation: Usually Parallel, Dicots: Netlike.
>Primary Vascular Budles in Stem: Monocot - Scattered, Dicot - In a ring.
>True secondary growth, with vascual cambium: Monocot - Rare, Dicot - Commonly present
What are 3 leave arrangements of a stem?
1. Spiral (Most common) a.k.a Alternate - One leaf at each node that forms a spiral.
2. Distichous (opposite) - Two leaves opposite each other at one node.
3 Decussate - Leaves that are at right angles to each other at one node.
4. Whorled - More three or more leaves at one node
What does Phyllotaxis stand for?
Arrangement of leaves on a stem
What is a Tracheophyte?
Vascular Plants (Plants that have a vascular system)
Give three overview examples of Trancheophystes
1. Ferns
2. Gymnosperms (Seed plants)
3. Angiosperms (Seed Plants, Monocot and Dicot)
What are lower plants?
Plants that don't produce seeds
Give an overview of Non-Vascular plants
1. Algae
2. Mosses & Liverworts
Give three examples of lower Plants
1. Algae
2. Mosses and Liverworts
3. Ferns
What are the two seed producing plants?
1. Gymnosperms
2. Angiosperms
What are the main functions of the roots?
>Anchorage
>Absorption
>Storage
What are the main functions of the Stem?
>Support
>Transport of water, minerals & photoassimilates (sucrose)
What is the main function of the leaves?
>Photosynthesis
What is a phytomere?
Modular growth that include the Node, internode, axillary bud, and leaf.
State what embyogenisis is.
The development of an embryo from a zygote
State what a Meristem is.
Undifferentiated plant tissue from which new cells arise
Give two examples of Apical Meristems
1. Shoot Meristems
2. Root Meristems
What is Indeterminate growth>
The unlimited growth of the plant from the shoot and root apex.
What is determinate growth?
Growth of limited duration. (e.g. leaves, flowers, and fruits)
What is an Axillary Bud?
A bud located where the leaf joins the stem
What is a Petiole?
The stalk on the leaf
What is Simple leaf?
the Lamina (Body of the leaf) and the petiole
What i a leaflet?
The parts of a compound leaf, they extend from the petiole but do not have axillary buds.
What is a Compound leaf?
A leaf divided into several distinct leaflets
Give five types of Simple leaves.
1. Entire
2. Lobed
3. Narrow
4. Toothed (ridged edges)
5. Divided
Define an Inflorescence
Flower cluster with definite arrangement of flowers
Explain what a Tendril is, its function, and what it is a modification of.
A modified leaf or stems, and supports shoots.
What is the function and modification of a Spines (of a cactus)
Modified leaves, and is used for protection
What is the function and modification of a Thorn.
Modified branch, and is used in the protection against browsing animals.
What is the function and modification of a Cladophyll
Modified stem, function in Photosynthesizing. (e.g. edible asparagus).
What is the function and modification of a Tuber?
Modified Stem (enlarged rhizomes, clusters of axillary buds, spiral pattern), function is used for food storage (e.g. potato)
What is the function and modification of Bulbs?
Modified stems with modified leaves, function is used for storage. (e.g. onion)
What is the function and modification of Corms?
Modified stems with small leave, function is for storage.
Briefly explain the structure of the Nucleus
Envelope: surrounded by a double membrane
Contains nuclear pores
Nucleolus: The dense center of the nucleus which contains RNA for RNA synthesis
Chromosomes: Complex of DNA and protein
Contains genes that govern the activity of the cell.
What is a tonoplast?
Membrane surrounding the Vacuole
Give two structured organelles that are surrounded by two Membranes.
1. Plastids
2. Mitochondria
Give three structured organelles that are surrounded by only one membrane
1. Vacuoles
2. Endomembrane system
3. Peroxisomes
Give three non-membrane bound plant components (organelle and non organelle components)
1. Ribosomes
2. Cystoskeleton
3. Oil Bodies
What is a Chloroplast.
Green pigmented Organelles that are the site of photosynthesis. Contain Chlorophyll and Carotenoid pigments.
Explain the orientation of chloroplast under the conditions of dim and bright light.
Dim light: Move their edges to cell wall to maximize light absorption.
Bright Light: Move perpendicular (sides orient away) to the cell walls to minimize light absorption and minimize photo damage
Explain the structures of Chloroplast.
They have a flattened membrane sacs called Grana. Thylakoid (membrane) and a homogeneous matrix called stroma . Grana are made up of the thylakoid membranes. Stroma thylakoids interconnect other grana thylakoids. They also contain oil bodies within the structure.
What is a Proplastid?
Colourless (or pale green) undifferentiated cells that differentiate into Chromoplast, Amyloplast, and Chloroplast.
Can Chloroplast develop into a Chromoplast? True or False?
TRUE
Briefly describe the structure and function of a Chromoplast.
Lacks chlorophyll, but has been synthesizes and retained caroteiod pigment, from chloroplast the internal membranes system disappears and cartenoids accumulate. This occures in the ripening of fruit. Function is somewhat unknown, but can be known to have co evolved to attract animals as to pollinate a plant.
Briefly explain the structure and function of Leucoplasts (Amyloplast)
least differentiates of the mature plastids, they lack pigment and inner membranes. The Amyloplasts synthesize starch, and other leuceoplasts are capable of forming oils and proteins.
What is transduction?
The process where Glucose is converted into sucrose which is then transported throughout the vascular system of the plant ploem.
Briefly explain the structure ad function of the Mitochondria.
Has a double membrane, the inner membrane which has invaginations (folds) called cristae, and an internal matrix. Functions as the site of cellular respiration; process involving teh release of energy from organic molecules and its conversion of ATP.
Briefly explain the structure and function of a Peroxisome.
Small spherical organelle, crystalline core (enzyme molecules), containing no internal membrane and closely released to the endoplasmic reticulum. It photorespirises.
Briefly explain the structure and function of a Vacuole.
Bounded by a tonoplast (one membrane) it is the largest cellular compartment and takes up most of the space within. Its function is to store food, dispose of waste, and aid in growth.
Briefly explain the structure and function of the Endomembrane system.
Contains the ER (Smooth and Rough). Rough ER contains Ribosomes on the outside surface. They are flat sacs. Smooth ER is long and tubular and functions in lipid synthesis. The Golgi System is flattened and disk shaped, forming a cis and a trans end and function ins the secretion of non-cellosic cell wall and polysaccarides.
Being apart of the Cell Cytokeleton, briefly explain the structure and function of Microtubules.
Are cylindrical structures about 24nm in diameter leaving a hole in teh center, tubulin ( alpha tubulin and Beta tubulin) are the polymer subunits that are twisted into a helix to form 13 rows (protofiliments). Its function is to old the cells internal stucture, its just found under the plasma membrane, to keep and order to cell expansion, and also are used as tracks for golgi veicles containing non-cellulosic cell wall substance to eh cell wall.
Being apart of the Cytoskeleton, briefly describe the structure and function Microfiliments.
Composed of actin polymer subunits formed into a helix with a smaller diameter of 2nm. Involved in the tip growth of pollen tubes, movement of the nucleus, organelle movement, and cytoplasmic streaming.
Briefly explain Cytoplasmic Streaming
A layer of Cytoplasm cycles around the cell - moving over a carpet of parallel filaments.
Breifly explain about Oil Bodies
Arises from the ER, most abundant in fruits and seeds.
What is the Principle component of Plant cell walls?
Cellulose
What is Cellulose made up of?
Repeating Monomers of Glucose attached from end to end
What are Micofibrils?
Bundles of Cellulose polymers
What does the Primary Cell walls of Plants compose of?
Cellulose, Hemicellulose, pectic substances, proteins
Explain the cellulose arrangement.
Has crystalline properties because of the orderly arrangement of it's molecules, so therefore the microfibrils wind together to form fine threads that may coil around one another giving it strenth the equivalence to steal at a cellular level.
Explain the role and structure of Hemicellulose.
Net-like framework cross-linked matrix of noncellulosic molecules. Polysaccarides. They are hydrogen bonded to to cellulose microfibrils and limit the cell overextending by tethering adjacent microfibrils.
Explain the role and structure of Pectin.
Intercellular substance that cements together walls of cells together and are highly hydrophilic polysaccarides. Hard to distinguish between primary wall and middle lamella
Descrbe the structure of the Secondary Cell wall
Starts forming whaen the cell has stopped growing and the primary cell wall is no longer increasing in surface area. Cellulose is most abundents in the secondary cell wall and is very ridgid. Has three disinct layers, S1, S2, and S3 layer
What is a Plasmodesmata
Cytoplasmic strands connecting the protoplasts of adjacent cells, in the primary cell wall.
What is a Pit Feild
A pit occures where the ajoining cells are connected
Briefly explain the Mitotic cell cycle
G1 Phase: Cell doubles in size, enzymes and organelles increase in numbers.
S Phase: DNA replicated and associated proteins synthesized; two copies of the cells genetic information now exists
G2 Phase: Structures required for cell division begin to assemble; chromosomes begin to condence.
M (Mitotic) Phase: The Two set of chromosomes are seperated and the cell divides.
IN the Mitotic Phase, what are the steps that lead to the seperation of the cell?
Early Prophase: chromosomes become visable as long threads.
MId Prophase: CHromosomes shorten and thicken until they consist of two threads (chromatids) and is attached by a centromere.
Late Prophase: kinetochores develope on both sides of each chromosome at the centromere. the nucleolus and the nucleous and nuclear envelope dissapere.
Metaphase: Spindle fibers appear and the chromosomes migrate to the equatorial plane of the spindle.
Anaphase: the sister chromatids split and are now called daughter chromosomes and move to opposite poles of the spindle fibre.
Telophase: Begins when daughter chromosomes have completed their migration
After telophase Cytokineses starts, explain the process and why it's different to animal cells?
A cell; plat matures at the center of the dividing cell. The cell does not pull apart like an animal cell. the plate grows withing the mother cell wall. When the plate fully separates the two side in then heads into inter phase.
Explain how the cell expands.
The cell expands mainly from the uptake of water by osmosis. Croos links of cellulose microfibrils embedded in the matrix of the cell wall are broken by enzymes. The restraint on the cell is reduced - results in water uptake and cell expansion.
What happens to the expansion of the cell if Microfibrils are oriented at right angles?
The cell will expand longitudinally along the axis.
What is cell Turgor
cell which is firm due to water uptake
What is meant by the term Solution
Homogenous, liquid mixture of 2 or more substances
What is meant by the term Solute?
Substance dissolved in solution
What is meant by the term SOlvent?
Dissolving agent of a solution
What is Bulk flow?
THe molecules of of water move together from one place to another due to the difference of potential energy.
What is Potential energy?
Stored energy of an object.
Explain the process of Diffusion.
The spontaneous tendency of a substance to move down its concentration gradient from more concentrated to a less concentrated area.
Explain Osmosis
Diffusion of water across a selectively permeable membrane. Involves the net flow of water. (from a low solute concentration to high level of solute concentration).
What are three types of water balanced cell concentrations.
Hypertonic solution: Higher solute solute concentration
Hypotonic solution: Low solute concentration
Isotonic: Both areas of concentration are equal.
What is Plasmolysis
A cell with low water potential water will leave the cell by osmosis. This will leave the protoplast (cytoplasm and its organelles) will shrink and thus the plasma membrane will pull away from the cell wall. The cell will have low Turgor.
What is Facilitated diffusion?
Carier proteins undergo conformational changes to transport a specific solute. (Substance movement of Polar molecules and ions). No ATP is required. Movement down a concentration gradient.
What is Active Transport?
Often involves protein pumps. Enables the cells to accumulate or expel solutes at high concentrations. (Substances movements of polar molecules and ions). It requires ATP to move solutes against the concentration gradient.
What are two ways the cells can move large molecules and particles (Vesicle-mediated transport).
Exocytosis: Releasing materials from the cell
Endocytosis: Taking materials into the cell
- Phagocytosis: Ingesting solids
- Pinocytosis: Talking up liquids
- Receptor-mediated endocytosis: Taking up specific molecules
What is Water Potential?
The physical property predicting the direction in which water will flow. (Governed by applied pressure and the concentration of solutes).
Explain the process of Water Potential.
(Low water Potential = High solute concentration
Hgh water potential = Low solute concentration)
Water moves from a region where the water potential is higher to a region where water potential is low.
What is the Water potential of pure waater at atmospheric pressure?
0 Mpa (Mega Pascals)
What happens to the water potential with the addition of solutes?
Lowers the water potential
What is meant by a flaccid solution?
Where the concentration gradient on both sides is Isotonic
Give three reasons why water potential in cells is important.
1. Protoplast turgor: High solute in vacuoles and plasma, water moves into cell, tugor pressure results.
2. Cell growth: cell wall loosening, water uptake = cell expantion.
3. Water stress: When water demand exceeds water supply = Water loss from plant body = wiling (cells plasmolyze) = cell death.
What are thee plant tissue and cell types systems?
1. Ground tissue and cell types
2. Vascular tissue
3. Dermal tissue
Under the tissue system 'Dermal tissue' what are the two tissue types? And their locations.
1. Epidermis: Outermost layer of cells of the primary plant body
2. Peridermis: Initial periderm beneath epidermis; subsequently formed periderms occur deeper in bark.
Under the tissue system 'Ground tissue' what are the tissue types, and their cells types. And thier locations.
1. Parenchyma tissue: Has Parenchyma cells, and arefound throught the plant body, paranchyma tissue in the cortex; pith and pith rays; in xylem and phloem
2. Collenchyma tissue: Has Collenchyma cells, On the periphery ( beneath the epidermis) in young elongating stems; often as cylinders of tissue or only in patches; in ribs along veins in some leaves.
3. Sclerenchyma tissue: Fiber cells- Sometimes in the cortex of stems, often associated with xylem and phloem; in leaves of monocots.
4. Sclerid cells - throught the plant
Under the tissue system 'Vascular tissue' waht tissue types, their cell types?
1. Xylem tissue: Tracheid - dead functional cells. Vessel elecments - deadfunctional cells.
2. Phloem tissue: Sieve cell - living at maturity, lacks nucleus, lacks cytoplams or vacoule.
Albuminous cell - associated with seive tubes but not derived from the same mother as seive cells.
Sieve-tube element
Coompanion cell - living to maturity, closely accosiated with seive tube elements and is derived from the same mother
What are the three primary meristems that derive fro the Apical meristem?
1. Protoderm
2. Ground meristem
3. Procambium
From the three primary meristems show which one derives into the three primary tissues.
1. Protoderm > Epidermis (dermal tissues system)
2. Ground meristem > Ground tissue (parenchyma, collenchyma, and sclerenchyma) (ground tissue sytem)
3. Procambium > Primary xylem adn primary phloem (vascular tissue system)
From the tip of the plant (apical meristem) to the base of the stem. Show where there highly differentiated cells and low differentiated cells.
From the apical meristem there is a low differentiation of cells, the midway down the stemt starts to differentiate from the primary meristems, and near the base of the stems primary tissues are distinct so therefore there are a high differentiated number cells.
Explain differenciation
The process by which cells that have identical genetic constitutions become different from one another
Explain the differnce between simple and complex tissue.
Simple tissue: Composed of only one type of cell (e.g parenchyma, collenchyma, schlerenchyma)
Complex tissue: Composed of more than one type of cell (e.g. xylem, phloem, epidermis)
Explain the structure and function of Parenchyma tissue, include transfer cells.
Occur in continuous masses. IN vertical strands cells. They are alive at maturity and are thinned walled. Rounded and surrounded by intracellular space and may contain chloroplasts.
Transfer cells: They are specialized parenchyma cells, they have wall in growths. They facilitate the movement of solutes over short distances. Correlated with the existence of intensive movement of solutes wither inward (uptake) or outward (secretion) across the plasma membrane. They occurs in association with the xylem and phloem, reproductive structures, glands.
Explain the structure and function of Collenchyma tissue.
Composed of Collenchyma cells that live to maturity. Often they are in long strands/ cyliders beneath the epidermis. They have cellulose thickening at the corners. Non lignified primary walls, which are soft and pliable. Well adapted for the support of young growing organs.
Explain the structure and function of Sclerenchyma tissue.
Composed of Sclerenchyma cells. They lack protoplasts at maturity. They have thick, often lignified, secondary walls. This is important in the strengthening and supporting the plant plats that have stopped elongating. They are in long slender fibres that occure in strands/ bundles.
Explain the structure and function of Sclereds (sclerenchyma cells).
They are short cells, are variable in shape and are often branched. They may occure singly or in aggregates through the ground tissue. They are found in the seed coats of many seeds and the stone (endocarp) of stone fruits.
What is the function of the Vascular system?
To transport water and other minerals, support the plant, and is used to store food.
Explain the structure and function of the Tracheary elements in teh Vascular tissues of Xylem.
Tracheids: Elongated, tapering, 1st and 2nd cell walls, pits but not perforations, lignified and are dead at maturity. Fibrous looking
Vessel elements: Elongated and stacked to form a vessel, they have 1st and 2nd cells walls. Has both pits and perforations. They are lignified and dead at maturity.
Vessel elements: The elongation of the tracheary elements stretch and cause helical (spiral) secondary cell walls thickening and perforation plates.
What is the meaning of Protoxylem?
During the period of elongation or expansion of the roots, stems, and leaves, the secondary walls of the first formed tracheary elements of the early-formed primary xylem, or Protoxylem. (Xylem that has been formed first)
What is th meaning of Metaxylem
The late forming primary xylem and the secondary xylem. Secondary cell walls of the trachieds and vessel elements cover the primary walls, except for the pit membranes and perforations of the vessel elements. These cells are called pitted elements, they are ridged and cannot be stretched. (Xylem that forms secondly)
Explain th structure and function of Sieve tube members
Seive tube elements: Elongated, with only primary cells wall and seive areas. They live to maturity but have no nucleus, they are stacked to form sieve tubes.
Seive tubes in gymosperms has no....
sieve plates
Explain the structure and function of the Dermal tissue
Protect the inside of the plant, to minimize water loss, and gas exchange. They are the outermost layer of cells of the entire plant. They are compactly arranged. A cuticle is on the outermost layer of the cells and consists of cutin and wax.
Explain the structure of the Stoma and guard cells within the epidermis layer of a plant.
They are unspecialized cells, the guard cells are concave in shape and they come in pairs to form a stomatal opening. Most abundant in the leaves.
What is the function of a root?
Ancorage of the plant, water absorption and conduction. Mineral uptake, nutrient storage.
What is the Radicle?
The fist protrusion from the embryo of the seed.
What is the Primary root?
The first root of the plant emerging from the radicle of the embryo. Also known as the tap root when it grows longer.
What are lateral roots?
Secondary roots that emerge from the side of the tap root.
What are adventitious roots?
Roots emerging from the stem or the leaves. They are also named prop roots and can be used as ancorage for teh plant also.
Are Monocots or Dicots found to have taproots?
Dicots.
What is a fibrous root system?
The lateral roots of adventitious roots give rise to roots that are not more prominent from one from the other. SO they are spread evenly.
Explain the Root Morphology.
Tip of the root: Covered by a root cap - cells that renew by new cells from the root apical meristem.
Three zones of the Root:
- Zone of Cell division: The zone of dividing cells from the apical meristem
- Zone of Elongation:Cell elongates leads to the increase in teh length of the root.
- Zone of Differentiation (Maturation) - Differentiation of cells, primary tissue matures, root hairs grow in this area.
Explain the structure and function of the root cap.
Made from living Parenchyma cells that protects the apical meristem and aids the roots for penetrating the soil. Mucilage lubricates the root during this passage.
Explain the structure and role of root hairs.
Root hairs grow from the Protoderm, and they increase the absorption surface area of the roots
How does the formation of Lateral root occur?
Grows from the Periderm (Below the endodermis of the vascular system).
Explain the structure and function of the Casparian strip.
Belt of waxy material (suberin and lignin). Lies within the endodermal cell walls.
-It blocks the passage of water and dissolved minerals.
-All substances entering the vascular cylinder must pass through the protoplast of the endodermal cells.
Explain the Symplastic and Apoplastic routs of mineral and water uptake through the roots and root hairs of a plant.
Symplastic: Mineral and water uptake goes through teh cells cytoplasm. Pathway through symplast.
Apoplastic: Mineral and water uptake goes through eh cells walls of the cells. Apoplast pathway.
Give and overview of the primary development of a dicot root.
Early primary growth
Completion of primary growth
Origin of vascular cambium (for secondary growth)
What are the differences between a monocot root and a dicot root?
Dicot: The vascular system (cylinder) is situated at the center of the root.
Monocot: THe vascular system is situated in a ring like structure around the center (pith)
Give an overview of the secondary development of a dicot root.
Formation of more secondary xylem and phloem
More secondary xylem and phloem plus periderm, cortex shed
The end of the 1st years growth.
What are some root adaptations?
1. Prop roots: Adventitious roots produced from the stem or leaves. (e.g. corn)
2. Storage roots: Food storage (e.g. kumara)
3. Pneumatophores: Aerial roots (negative gravitropic -upward- growth, for aeration to root system (e.g. mangroves)
From the Primary tissues of the Vascular system what are the secondary tissues that form?
Pericycle (Below the endodermis):
- Cork cambium > Cork and Phelloderm
- Vascular Cambium > Secondary Phloem and Secondary Xylem
Undifferentiated Procambium:
- Vascular Cambium . Secondary phloem and secondary xylem
What is the definition of a shoot?
The above ground proportion of a vascular plant.
What is the difference between Primary and Secondary growth.
Primary growth: Growth originating in the apical meristems of the shoot and root. Lead to the increase in height.
Secondary Growth: Growth derived from lateral meristems, leads to the increase in girth.
What is a Herbaceous plant?
They have primary primary growth and little or no secondary growth
What is a Woody plant?
Plants that have Primary and secondary growth.
What are the three Primary meristems that give rise to primary tissues?
1. Proterderm
2. Procambium
3. Ground Meristem
Explain the structure of the Tunica-corpus organisation.
Tunica layers: There are two layers of this layer and have an Anticlinal division of their cells (they divide sideways)
Corpus: Initial layer and have both anticlinal division and periclinal division ( the cells divide horizontally).
Tunical = L1 and L2
Corpus = L3
L= Layer.
WHere is the TUnica-corpus found in the plant?
THe Apical meristem
What is the difference between the leaf primordia and the bud primordia
Leaf Primordia: They give rise to the developing leaves
Bud Primordia: Give rise to lateral shoots.
What is the Apex?
Nodes and internodes compressed from the Apical meristem
What happens toteh region below the apex?
Growth in length of stem, formation of internodes. Cell divisions and cell elongation.
What is the Phytomere?
The regions of the shoots that include the leaf, node, internode, and axillary bud.
What is the difference between Monocot stems and Dicot stems?
Dicot: Has either a continuous or a discrete circular arrangement of the vascular cylinders/bundles around the pith in the center.
Monocot: Has a scattered arrangement of the Vacular bundles around the whole stem whithin the ground tissue.
What is the difference between the Continuous and Discrete arrangement of the Vascular Bundles/Cylinders within a Dicot plant.
Discrete: Vascular bundles forma single ring around the pith, ground tissue is also between these vascular bundles called interfasicular regions that connects the cortex with the pith.
Continuous: The vascular system appears as a continuous hollow cylinder around the pith.
What is a leaf trace?
The vascular tissue of each leaf is continuous with the vascular bundles of the stem.
What is wood?
Is the secondary Xylem
What are the two Lateral Meristems, and what do these meristems produce?
Vascular Cambium: Forms secondary xylem and phloem
Cork Cambium: Forms cork and phelloderm
Vascular cambiums are highly vacuolated. True or False?
TRUE
What are fusiform initials?
The vascular cambium which are vertically oriented and are several time longer than they are wide. Parallel to the stem or root axis.Has fusifom ends
What are Ray initials?
Horizontally oriented Vascular cambium which are slightly elongated or squarish. Perpendicular to stem or root axis.
In which direction do the secondary xylem and phloem form from the Vascular Cambium?
Secondary Xylem: Towards the inside of the vascular cambium
Secondary Phloem: Towards the outside of the vascular cambium.
What are the origins of the Fascicular cambium?
Arises from the procambium. Between the Primary xylem and phloem.
What are the origins of the Interfascicular cambium
Arises from parenchyma cells (rays), found between teh te vascular bundles. Known as the pith rays.
What do Fusiform initials give rise to and what are their function?
The give rise to:
- Trachieds
-Vessel elements
- Sieve tube elements
- Fibres of Xylem and phloem
They function is in long distance transport + support
What do Ray initials give rise to and what are their functions?
They give rise to:
- Vascular Rays (radial files of parenchyma cells)
Functions is short distance transport, they are living avenues between the xylem and phloem.
What three parts does the Periderm Consist of?
1: Cork Cambium (phellogen), which produces the periderm
2: Cork (phellem), protective tissue formed to teh outside by the cork cambium.
3: Phelloderm: A tissue that resembles the cortical parenchyma, formed inside by the meristem.
Cork(outside) -------Cork Cambium(middle)-------Phlloderm(inside)
What are Annual rings?
Growth Rings for 1 year of the plants growth.
Inner layer: Spring wood - Early ( less dence -wider cells and proportionally thinner walls)
Outer layer: Summer wood - late (narrow cells and proportioally thicker walls
Explain what Bark is.
All tissues outside the Vascular Cambium.
Inner Bark: Tissues between cork cambium and vascular cambium. Living tissue.
Outer Bark: Tissues outside the cork cambium. Dead tissue.
What are Lenticles and their function?
Spongy area in the cork surface of stems/roots. Allows for gas exchange through the periderm.
Give and Overview of Secondary growth from Primary tissues:
Ground Tissue:
-Cortex > Cork Cambium> Cork, Phelloderm
-Pith, Pith Rays> Interfascircular Cambium> Vascular Cambium > Secondary Xylem and Phloem
Procambium:
- Undifferentiated Procambium> Fascircular Cambium> Vascular Cambium> Secondary Xylem and Phloem.
What is Sessile
A leaf with no petiole
What is a sheath?
Expansion of the base of teh leaf encircling the stem (in monocots)
What is a double compound leaf?
Each leaflet is divided into smaller leaflets
Give an overview summary of the dicot and monocot leaf morphology.
Dicot:
-Simple or compound
-Lamina
-Petiole
-Stipule
-Reticulate venation
-Compound (Pinnate or palmate, leaflets)
Monocot:
-Lamina
-Sheath (no petiole)
-Ligule
-Parallel venation
What is a ligule?
A scale-like outgrowth
What is a Mesophyte
Plants that require an environment that is neither to wet or to dry
What is a hydrophyte?
Plants that require a large supply of water or grow whlly or partly submerged in water.
What is a Xerophyte
Plants that adapt to arid habitats (where there is little to no water)
Give an overview of a Dicot leaf structure
Epidermis:
-Upper and lower epidermis
- Cuticle
- Stomata
- Guard cells
Mesophyl:
-Spongy parenchyma and palisade parenchyma
Vascular bundles
What is the structure and function of the leaf epidermis.
Structure:
Compact structure
-Many stomata within the lower epidermis of the leaf
Function:
-Protection
-MInimises water loss
-Gas exchange via stomata
What is the arrangement of the stomatal openings in a dicot and a monocot?
Dicot: Random arrangement of stomata
Monocot: Shows parallel arrangement of stomata.
What are trichromes?
Epidermal hairs, outgrowths of the epidermis
Describe the structure of the mesophyll
Structure:
-Ground tissue of the leaf:
+Sandwiched between the upper and lower epidermis
+ Consists mainly of parenchyma cells
-chloroplasts for photosynthesis
+ Palisade mesophyll
- cells have columnar shape
+ Spongy mesophyll
- cells have an irregular shape
- large air spaces between cells
Describe the functions of the mesophyl
Functions:
- Numerous chloroplasts in cells
-Intracellular spaces linked to outer atmosphere through stomata
- Gas exchange
+ uptake of Co2 release of O2
Describe th structure and function of the Vascular bundles:
Structure:
- Continuous with xylem and phloem of the stem (leaf traces)
- Xylem towards upper leaf surface
Function:
- XYlem brings water and minerals ti the phtosynthetic tissue
- Phloem carries sugars and other organic products to other parts of teh plant
What is the Bundle sheath?
Layer of cells surrounding the vascular bundle in the leaf (parenchyma cells and schlerenchyma cells)
What is the difference between C3 and C4 plants?
C3: Plants in which the first product of CO2 fixation is a C# compound.
-3-phosphoglycerate
C4: Plants in which on of the first products of CO2 fixation is a C$ compound
- oxaloacetate
What is the difference in the mesophyll in grass leaves than from normal leaves?
The mesophyll in many grasses are similar in shape and have no distinction between palisade and spongy tissue
Give an overview of the C4 grass leaf anatomy
- Mesophyll cells and bundle sheath cells form 2 concentric layers around the vascular bundle. The bundle sheath contains many large chloroplasts.
Give an overview of the C3 grass anatomy leaves
Mesophyll cells and bundle sheath are not concentrically arranged around the vascular bundle. Bundle sheath cells have small chloroplasts.
What is a leaf abscission?
Dropping of a leaf from a branch
What are the leaf abscission zones?
#NAME?
What is the leaf scar?
The protection layer on the stem from where the leaf had dropped off.
What is oxidatin and reduction, explain the difference.
Oxidation: X - e- -------> X+
Reduction: Y + e- -------> Y-
What is the chemical process of photosynthesis
Energy + 6CO2 + 6H2O ----> C6H12O6 + O2
carbon dioxide + water -----> glucose + oxygen
What is the chemical process of Respiration
C6H12O6 + 6O2 ------> 6CO2 +6H20 + Energy
Glucose + Oxygen -----> Carbon dioxide + water
What is entropy?
a measurement of disorder, or randomness in a system
What is an enzyme?
Are catalyst of biological reaction, lowers activation energy, increases the reaction rate
Describe the structure of an enzyme
A large globular protein molecule, reacting molecule that binds with a substrate. THe substrate fits into the active site.
Describe what a cofacter is.
Enzymes require cofactors
- Metal ions
- non-protein organic molecules
What is ATP and what is its function?
Stands for Adenosine triphosphate.
Adenine (nitrogenous base) + Ribose (5C sugar) + 3 phosphate groups.
It supplies the most energy for the most activities in the cell.
How does ATP produce free energy?
Hydrolysis of ATp is accompanied b release of free energy, -30KJ/ mol.
The enzyme ATPas
What are some examples of teh use of ATP
membrane pumps fro the transport of ions.
Flagella movement, cytoplasmic streaming.
Catalysis of energy requiring reaction.
What is Energy coupling?
Endergonic reactions are powered by energy released in exergonic reactions
ATp is intermediate carrying energy from one to the other.
What is is spontaneous reaction and what is a non-spontaneous reaction and give and example of these reactions within Energy coupling using ATP hydrolysis.
Endergonic: deltaG is positive, reaction is not spontaneous and takes in energy.
- Glutamic Acid + ammonia -----> Glutamine DeltaG +3.4 Kcal/mol
Exergonic: DeltaG is negative, reactionis spontaneous, and gives off energy.
- ATP + H2O --------> ADP + P DeltaG -7.3Kcal/mol
Coupled reaction: Over all deltaG is negative so together there is a spontaneous reaction. (-7.3 + 3.4) or (3.4+ (-7.3)) = -3.9 kcal/mol
What is respiration?
The controlled oxidative breakdown of glucose to CO2 and water. The energy taken from the breaking of covalent bonds is used to make ATP.
Give an overview of teh three phases in Respiration
1. Glycolysis
2. Citric acid Cycle = Krebs cycle
3. Oxidative phosphorylation
What is the difference in the Respiration of a plant during the night and day.
Darkness (Underground or when stomata is closed): Is important in maintaining cellular processes.
Light: Some CO2 released by respiration is immediately used by photosynthesis.
Where does glycolysis happen within the cell?
Cytosol
Where does the citric acid cycle proceed within the cell.
The mitochondrial matrix
Where does the oxidation phosphorylation and electron transport process happen in the cell?
The mitochondrial matrix
Explain the first 5 steps of the Preparatory phase within Glycolysis.
Energy investment: 2ATP.
Step 1: THe terminal phosphate of an ATP molecule is tranferred to the glucose to produce glucose 6-phosphate and ADP.
Step 2: The glucose 6-phosphate is rearranged, becoming Fructose 6-phosphate
Step 3: Second prepatory reaction. The fructose 6-phosphate gains a second phosphate to form fructose 1,6-biphosphate as another ATP is converted to ADP. Energy yeild is -2ATP.
Step 4: The cleavage step from which glycolysis derives its name. The six-carbon sugar molecule is split in half, producing two-carbon molecules (glyceraldehyde 3-phosphate and dihydroxyacetone phosphate).Th dihydroxyacetone phosphate is converted to glyceraldehyde 3 phosphate.
Step 5: There are two molecules of glyceraldehyde 3-phosphate. therefore the products of subsequent steps must be counted twice to account for the fate of each glyceraldehyde 3-phosphate molecule.
Explain the last 5 steps (6-10) of the Payoff phase within Glycolysis.
Step 6: Two molecules of NAD+ are reduced to two molecules of NADH. IN this step some of the energy from the oxidation of glyceraldehyde 3-phosphate is stored as high-energy electrons in the NADH
Steps 7-10: Two molecules of ADP take energy from teh system, forming two molecules of ATP per molecule of glyceraldehyde 3-phosphate- or four molecules of ATP per molecule of glucose. Two of the four ATP are, in effec, replacements for the two ATP used in STEPS 1 and 3. The net ATP yield is only two molecules od ATP per molecules of glucose. THe formation of ATP by the enzymatic transfer of a phosphate group from a metabolic intermediate to ADP, as occures in steps 7 and 10, is refered to as substrate level phosphorylation.
Glycolysis ends with most of the energy of the original glucose molecule still present in the two pyruvate molecules.
Give an overview of Glycolysis process
Glucose is split into pyruvate.
The first phase in oxidation of glucose is glycolysis, in which six-carbon glucose molecule is split into two three carbon molecules of pyruvate. this reaction occurs in the cytosol of a eukaryotic cell and results in the formation of two molecules of ATP and two NADH
Give an overview of the Citric acid cycle
It completes the metabolic breakdown of glucose to carbon dioxide.
IN the course of respiration, the three carbon pyruvate molecule from glycolysisare oxidized in teh mitochondrial matrix to two-carbon acetyl groups, which then enter the citric acid cycle as acetyl COA.
IN the citric acid cycle, each acetyl group is oxidized in a series of reaction to yeild two additional molecules of carbon dioxide, one molecule of ATP, anf four molecules of reduced electron carriers (three NADH and one FADH2).
With two turns of teh cycle, the carbon atoms derived from the glucose molecule are completely oxidized and released as molecules of CO2.
Give an overview of the Electron transport chain.
The flow of Electrons is couples to the pumping of protons across the inner mitochondrial membrane and the synthesis of ATP by oxidation phosphorylation.
The eectron transport chain involves a series of electron carriers and enzymes embedded in the inner membrane of the mitochondrial. Along this series of electron carriers, the high-energy electron carried by NADH and FADH2 move downhill energeticaly, ultimatly reducing oxygen to water.
The large quantitiy of free energy released during the passage of electrons down the electrons down the electron transport chain powers the pumping of protons (H+ ions) out of the mitochondrial matrix. This creates an electrochemical gradient of potential energy across the inner membrane of the mitochondrion.
When protons pass through the ATP synthesase complex as they flow down the gradient back into the matrix, the free energy released is used to form ATP from ADP and phosphate. this process, known as chemiosmotic coupling, is the mechanism by which oxidative phophorylation is accomplised.
In the course of teh aerobic breakdown of glucose molecule to CO2 and H2O, 36 molecules of ATP are generated, most of them in the MItochondrion in the final stage of respiration, oxidative phosphorylation.
What is the chemical process of photosynthesis.
Energy + 6CO2 + 6H2O -----> C6H12O6 + 6O2
carbon dioxide + water ------> glucose + oxygen.
Define photosynthesis
Chloroplast capture light energy from the sun and convert it to chemical energy stored in sugar and other organic molecules.
Where does photosynthesis ocuure?
The chloroplast within the mesophyll cells
What happenes within the mesophyll cells during photosynthesis.
O2 exits and CO2 enteres the mesophyll cells through the stomata.
From the visible light spectrum, what wavelengths correspond to the colours.
Violet light: Shortest wavelength (380 nano meters) to red light (750 nano meters). Dark to light blue (400 -500 nano meters), green to yellow (500 - 600 nano meters)>
Describe the structure of the Chloroplast
Two membranes (outer and inner)
Thylakoid = mebraneous sacs
- thalakoid membrane
Thalakoid stacked into columns called grana
Describe the absorbtion spectrum of the different chlorophyll
Chlorophyll a: Most abundant absorbtion around the violet and red light spectrums.
Chlorophyll b: Same a chlorophyll a, but has the highest peak and is closer to the lighter blue to green spectrum
Caretenoids: Smallest absorbtion peak, around the violet and blue light spectrum
What is a pigment?
A substance that absorbs light photons.
What is the action spectrum for photosynthesis
The resemblance to the absorption spectrum for chlorophyll a but no exact match
Partly due to light absorption by accessory pigments.
Shows the relative effectiveness of different wavelengths of lighr for photosynthesis, similarities between absorption and action spectrum provide evidence that a pigment is responsible for the process.
Explain the role and the structure of Chlorophyll a
Green main photosynthetic pigment
N containing porphyrin ring
Mg atom held in porphyrin ring
Hydrophobic tail
- Anchores molecule to proteins in the thalakoid membrane
Explain the role and structure of Chlorophyll b
It is an accessory pigment
Involved in capture of light
-CHO group instead of CH3 (at the top right hand corner of teh ring)
Explain the role of a Carotenoid pigment
It is an accesory pigment
Red, orange and yellow
Embedded in the thylakoid membranes
Absorbtion/ dissipation of excessive light energy (photoprotection)
How is an isolated chlorophyll excited by light?
The absorption of a photon causes a transition of the chlorophyll molecule from its ground state to it's excited state.
Explain the antenna complex and the reaction center.
It consists of pigment molecules that gather light and funnel it to the reaction center. It is like a satellite dish in a way. A complex of proteins and chlorophyll molecules are bound at the center, these are special chlorophyl a molecules and are able to absorb the phtotons.
How does a photosystem harvest light?
The photon stikes the Light harvesting complex (LHC) the energy passed on from molecules to molecules (within the anntenna complex) until it reaches the reaction center. An excited electron from 1 of 2 special chlorophyll molecules is captured.
What is the difference between Photosystem I and Photosystem II?
Photosystem I: has a special pair of chlorophyll a molecules of the reaction center known as P700. Th P stands for the pigment and the 700 subscript designates the optimal absorbtion peak in nano meters.
Photosystem II: Also contains a special pair of chlorophyll a molecules. Its optimal absorbtion peak is at 680 nano meters. P680
Explain the processes of both Photosystems II, and I
Light enters Photosystem II, where it is trapped by pigment molecules and passed to the P680 chlorophyll molecules of the reaction center. Energized electrons are transferred from P680 to the electron acceptor. As the electrons are removed from P680, they are replaced by low-level electrons from water molecules, and oxygen is produced (splitting water -water photolysis).
Pairs of electrons then pass downhill to Photosystem I along an electron transport chain. This passage generates a proton gradient that derives the synthesis of ATP from ADp and phosphate (photophosphorelation). Meanwhile, light energy absorbed in photosystem I is passed from P700 chlorophyll molecules of the phtosystem I reaction center. the energized electrons are ultimatley accepted by the coenzyme molecule NADP+, and the elctrons removed fro P700 are replaced be the electron from photosystem II.
The energy yield from the light-dependent reactions is stored in the molecules of NADPH and in the ATP formed by photophosphorylation. Photophosporelation also occures in cyclic electron flow, a process that does not require Photosystem II. The only product of cyclic electron flow is ATP and NADPH in a 3:@ ratio.
Explain the process of Chemiosmotic coupling of PHotorespiration
Photophosphorylation in chloroplasts is a chemiosmotic process. As electrons flow down the electron electron transport chain from Photosystem II to Photosytem I, protons are pumped from the stroma into the thylakoid lumen greating a gradient from the thalkoid lumen back into the stroma, they pass through an ATP sunthase, generating ATP.
What is the outcome of light reactions (light dependent)
Oxygen: from the photolysis of water
NADPH: From the reduction of NADP+
ATP: from ADP using H+ gradients
What is the overview Carbon fixation Reactions (Calvin Cycle)?
At each turn of the calvin cycle, RuBP is regenerated
Most of the fixed carbon is converted to either sucrose or starch
Explain the process of the Calvin Cycle.
CO2 is fixed via Three-carbon pathway.
IN the carbon-fixation reactions, which take place in teh stroma of the chloroplast, the NADPH and ATP produced in the light reactions are used to reduce carbon dioxide to organic carbon. The calvin cycle is both responsible for teh initial fixation of CO2 and for the subsequent reduction of teh newly fixed carbon.
In teh Clavincycle, a molecule of CO2 combines with the starting compound, a five-carbon sugar called ribulose (1,5-bisphosphate -RuBP-), to form two molecules of teh three-carbon compound 3-phosphoglycerate (PGA)> the PGA is then reduced to the three carbon molecule glyceraldehyde 3-phosphate (PGAL), with electrons provided by NADPH and enrgy provided by ATP hydrolysis.
At each turn of teh Calvin cycle, one carbon atom atom enters the cycle. three turns of teh cycle produce one molecule of glyceraldehyde 3-phosphate. At each turn of the cycle, RuBP is regenerated. Most of teh fixed carbon is converted to either sucrose or starch.
Explain Photorespiration the amount of products within the process.
High CO2/ Low O2:
-Rubisco has carboxylase activity
+ Catalyzes carboxylation of Ribulose 1,5 bisphosphate
+ efficient carbon fixation
High O2 / low CO2:
- Rubisco has oxygenase activity
+ Catylyzes condensation of O2 and BuBP to form phosphoglycolate
+ no carbon fixation, energy expensive
What is the Difference between C3 and C4 plant photosynthesis?
C3 plants:
-First product of CO2 fixation is 3-PGA
-Calvin cycle only
C4 Plants:
-First detectable product of CO2 fixation is OAA (oxaloacetate)
-OAA = C$ compound
-Calvin cycle and C4 pathway
Explain C4 photosynthesis occurances.
C4 pathway takes place in the Mesophyll cells, but the calvin cycle occurs in teh bundle-sheath cells.
Why are C4 plants more efficient users of CO2 than C3 plants?
PEP carboxylase is not inhibited by O2. thus, C4 plants can attain the same photosynthetic rate as C3 plants, but with smaller stomatal openings and, hence, with less water loss. In addition, C4 plants are more competitive than C3 plants at high temperatures.
- not inhibited by O2
-no photorespiration in mesophyll cells
-has a higher affinity for CO2 than rubisco
Give a brief summary of Photosynthesis energy flow.
#REF!
Give a brief summary of Respiration Energy flow.
#NAME?
What is Transpiration?
Loss of water vapor by plant parts
What is the pathway of water molecules in a plant leaf.
1. Evapouration of water from cell surfaces bordering intercellular space.
2. Diffusion of water vapor into atmosphere b way of stomata
Why is transpiration known as the 'Unavoidable evil'?
The uptake of CO2 for photosynthesis and the loss of water by transpiration are inextricably bound together.
Give the example of driving forces of water potential.
Wet soil: High water potential = -0.1 Mpa
Dry soil: lower water potential = -0.3 Mpa
High Humidity: higher water potential = -14.2 Mpa
Low humidity: lower water potential = -100.0 Mpa
Within the vascular bundles; where does the water travel through the plant.
Conducted through the Vessels and Tracheids of the Xylem
Explain the process of Transpiration
It generates a pull on teh water column in the xylem.
Negative pressure at the air-water interface causes water to move up through the xylem.
What is Cohesion and what is tension?
Cohesion of water due to hydrogen bonding and adhesion to cell walls.
The upward pull on the sap creates a tension within the xylem.
What are adaptations that minimize water loss
Cuticle:
- Impervious to water (and carbon dioxide)
Stomata:
- Opening and closing controls water loss
Explain the systematic opening and closing of stomatal openings.
Results from the change in tugor pressure within guard cells.
- Increase is cell tugor: Stomata opening
- Decrease in turgor: Stomata close
Radial orientation of cellulose microfibrils in guard cells
- Turgor increase: Cells increase in length more than width.
- Increase in length causes buckling as cells are attached at the tips.
Explain the role of Potassium in Stomatal movement
Reversible uptake and loss of K+ ions by guard cells leads to change in turgor pressure.
Guard cells accumulate K+ from neighboring epidermal cells.
Water potential decreases
Water enters by osmosis.
What is the relationship between transpiration and water uptake.
The rise in water uptake is a response to the rise in transpiration.
(On a graph, transpiration rises to a peak, and following behind is the rise of water uptake to a peak. Transpiration hits its peak before water uptake and starts to decrease. When it goes down water uptake hits its peak and starts to go down)
What are some factors in the cause of the opening/closing of the stomata.
CO2 deficiency - Open
Light - Open
Water deficiency - Close (ABA mediated)
Circadian rhythm - day open/ night closed
What is the Circadian rhythm?
The opening and closing of the stomata; where the stomata is open during the day and closed during the night.
Explain the uptake of water by roots.
Uptake of water by roots takes place largely through the root hairs. No input of energy required, follows water potential gradient from soil - root. Aquaporins (transport proteins) affect the rate of water diffusion.
Explain the uptake of Minerals by roots
Requires active transport, and an input of energy (ATP) is required. Mineral composition of root cells differs from the medium the plant grows in.
What are the driving forces of transpiration within the roots system and within the plant?
Soil water = -0.02 Mpa
Xylem sap = -0.02 M pa
Mesophyll cell = 2.0 MPa
Air = -95.0Mpa
How is water transported within the xylem?
Water moves down a water potential gradient, soil - plant - air continuum. transpiration stream in xylem.
Mechanism: Cohesion-tension
-Cohesion of water molecules
- Stable water column formed
Result: Xylem under tension
= negative pressure
What is root pressure and why does it happen?
When transpiration is slow (e.g. at night time) water still need to be supplied to the plant so.
Ions are secreted in the xylem so that water potential decreases. when that happens it gives water that high to low water potential gradient so that it can move passively into the root.
Root pressure is created and the water is moved up into the xylem, it forces water and dissolved ions up into the xylem.
What is Translocation?
long distance transport of "food" (assimilates) in the phloem.
What are assimilates?
Sugars manufactured in photosynthesis.
What is Assimilate partitioning
Pathway of assimilate flow in plant
What are the reaction in Mesophyll cells.
Chloroplasts:
- Glucose stored as starch in chloroplasts during the day
- Hydrolysis of starch to glucose at night.
Cytoplasm:
- C3 compounds synthesized into glucose and fructose
- Sucrose sxport from mesophyll cells
Explain assimilate transport which follows a source to sink pattern
Sources: Sites where sugars are produced by photosynthesis or breakdown of starch. Exporters of assimilates. (Example - leaves)
Sinks: Sites where sugars are consumed or stored. Importers of assimilates (Examples - growing shoot and root tips)
What are Sinks?
All plant parts unable to meet their own nutrition needs may act as sinks, that is, importers of assimilates and as sources when they are exporting assimilates.
What do storage tissues act as?
Sinks: When importing assimilates
Sources: When exporting assimilates
What is the evidence for assimilate transport in phloem?
Ring-barking (girdling) of trees:
= removal of Phloem.
+ Observation: Swelling of stem above the ring.
+ Explanation: Formation of new bark and wood by accumulation of assimilates.
What is radioactive tracers and why does it prove evidence of sugar transport in Sieve tubes (Phloem).
Radioactive assimilates (14C-labeled sucrose) not only confirmed the movement of such substances in the phloem but have also shown conclusively that sugars are transported in the sieve tubes.
What is the Pressure-flow hypothesis?
Assimilates travel from source to sink along a gradient of tugor pressure.
Why do Aphids feed fro the phloem sap?
Aphids have modified mouth parts (Stylets) into the stem or leaf and puncture the sieve tubes. the pressure of the sieve tube then forces the sieve tube sap through the aphids digestive tract and out through its posterior end and droplets of honeydew.
What is the composition of phloem sap?
10 to 25% of phloem sap contains dry matter, 90% of that dry matter or more is sugar (Mainly sucrose)
Explain the Pressure flow mechanism.
1. Loading of sugar into sieve tube at source reduces water potential inside sieve tube. water uptake by osmosis.
2. water uptake generates positive pressure that fources sap to flow along the tube.
3. Pressure relived by unloading sugar and consequent water loss at sink.
4. Xylem can recyle water from sink to source.
What is phloem loading?
Decreasing the water potential in a sieve tube and causes water entering the leaf in the transpiration stream to move into the seive tube by osmosis.
What are modes of transport through the plasma membrane?
Passive Transport:
- Simple didiffusion
- Facilitated diffusion
+Carrier mediated
+ Channel mediated
Active transport.
Explain the process of Passive transport.
#NAME?
Explain the process of Active transport
#NAME?
What can move through a membrane by Simple diffusion? (Passive)
#NAME?
What can move through a membrane by facilitated diffusion (Passive)?
Carrier Mediated:
- bind specific solute
- Undergo conformation changes
Channel Mediated:
- ALlow selected solutes to pass through water filled pore
- Passage only what 'gate' is open
What can move through a membrane by Active transport?
Any solute that can be transported by a Transport protein: PUmp
Moves solutes against the concentration gradient or electrochemical gradient. ANd, requires ATP.
What are the Essential Macronutrients for the plant including their forms.
Carbon (C) - form: CO2
Oxygen (O) - form: O2, H2O, CO2
HYdrogen (H) - form: H20
Nitrogen (N) - form: NO3, NH4+
Sulfur (S) - form: SO4,2-
Phosphate (P) - form: H2PO+, HPO4,2-
Magnesium (Mg) - form: Mg2+
Calcium (Ca) - Ca2+
Potassium (K) - form: K+
What are the roles of the Macronutrients within the plant.
C,O,H - In carbohydrates, lipids
N - In amino acids, proteins, nucleic acids, chlorophyll
S - In some amino acids, cofactors
P - IN ATP, ADP, nucleic acids
Mg - In chlorophyll
Ca - In cell wall, cofactors of enzymes
K - for Ion balance, stomata openings
What Macronutrients are obtained from the soil.
Nitrogen, Potassium, Calcium, Magnesium, Phosphorus, Sulfur.
What Macro nutrients are obtained from water of Carbon dioxide
Hydrogen, Carbon, Oxygen.
What are the Nicronutriens the plant uses and what are their forms
Chlorine (CL) - form: Cl-
Iron (Fe) - form: Fe3+, Fe2+
Boron (B) - form: H3BO3, H2BO3-
Manganese (Mn) - form: Mn2+
Zinc (Zn) - form: Zn2+
Copper (CU) - form: CU+, CU2+
Nickel (Ni) - form: Ni2+
Molybdenum (Mo) - form: MoO4,2-
What is the difference between Macronutrients and Micronutrients.
Macronutrients is what the plant uses quite a lot of
Micronutrients is what the plant uses little of
What is a Hydroponic CUlture?
Plants that are grown in mineral solution without soil
What are the Deficiency symptoms of Macronutirents in a plant?
NItrogen: General chlorosis, especially in older leaves; in severe cases, leaves become completely yellow and then become tan as they die; some plant exhibit purple colouration due to the accumulation of anthocyanins
Potassium: Mottles or chlorotic leaves with small spots of necrotic (dead) tissue at te tips and argins; weak, narrow stems; mostly older leaves affected.
Calcium: Shoot and roots tips die; young leaves at first hooked, then die back at tips and margins, devaloping cut-out apperances at these sites.
Magnesium: Mottled or chlorotic leaves; may redden somtimes with necrotic spots; leaf tips and margins turned upwards; mostly older leaves affected; stems slender
Phosphorus: Plants dark green, often accumulating anthocyanins and becoming red or purple; in later stages of growth, stems stunted, oldest leaves becoming dark brown and die.
Sulfur: Young leaves with light green veins and interveinial areas; chlorosis initially in mature and young leaves, rather than in olde leaves as with nitrogen deficiency.
How does a plant proceed with Nitrogen Fixation?
Nitrogen fixing bacteria are in symbiotic relationship with vascular plants.
Roots of leguminous plants form root nodules.
the bacteria of a nodule supply the plant with fixed nitrogen obtain sugar from the plant and, e.g. Rhizobium bacteria produce root nodules in white clover, kowhai, native booms, gorse.
What is Nitrogen fixation?
The incorporation of atmospheric N2 into organic compounds containging N.
N2 is reduced to NH4+
N2 + 8e- + 8H+ + 16H20 -----> 2 NH3 +H2 +16ADP + 16P
Describe the development of a root nodule
The development of a nitrogen-fixing root nodule depends on chemical dialogue between Rhizobium bacteria and root cells of their specific plant hosts
Describe the stages in the development of a root nodule
1. Root emits a chemical signal that attracts the Rhizobium bacteria
2. Bacteria stimulate formation of infection thread (root hair)
3. The bacteria penetrate the cortex within the infection thread.
4. The developing root nodule and grows outwards
What is a Mycorrhiza
Symbiotic fungi that associates with the plants roots.
-Found in most vascular plants species
-Important for increasing water and phosphate uptake
Explain the Mycorrhiza and its symbiotic plant nutrition.
Mycorrhizae: Are modified roots consisting of mutualistic associations of fungi and rotos
The Fungus: Benefits from a steady supply of sugar donated by the host plant
In return, the FUngus: Increases the surface area of water uptake and mineral absorption and supplies water and minerals to teh host plant.
What are two main types of Mycorrhizae
1. Ectomycorrhizae: The mycellium of teh fungus forms a dense sheath over the surface of the root.
2. Endomycorrhizae: Microscopic fungi hyphae extend into the root. = Abiscular mycohiza
WHen is flowing induced by the environment?
Leaves perceive daylength, buds respond by flowering
When is Tuberisation induced by the environment?
Leaf perceives daylength, underground stolon responds by forming a tuber
What is (Positive) Phototropism?
THe recognition that the plant bends towards the light.
Explain the process of positive Phototropism
1. the tip of the coleoptile percieves the light
2. The light 'response' is transmitted away from the tip
3. Curvature occures in the elongating cells in the cortex below the tip
What is the role of Plant hormones?
PLay a major role in coordination of the plants growth and development
What are the major group plant hormones?
#NAME?
Explain the chemical nature, site of biosynthesis, transport, and effects of the hormone Auxin.
Chemical Nature: indole-3-acetic acid (IAA) most naturally ouccuring auxin.
Site of Biosynthesis: Primarily in leaf primordia and young leaves and in developing seeds.
Transport: Is transported both polarly (undirectionally) and nonpolarly.
Effects: Apical dominance; tropic responses; vascular tissue differentiation; promotion of cambial activity; induction of adventitious roots on cuttings; inhibition of leaf and fruit abcission; ihibition or promotion (in pineapples) of flowing; stimulation of fruit development.
Explain the two mechanisms of AUxin transport in plants
1: Polar Auxin Transport - Proposed to be important during embryogenesis and early seedling, and in tropic (directional growth).
2: Non-polar Auxin Transport - Transport of IAA that originates in leaves is transported in the phloem under mass-flow of sucrose.
Faster velocity than polar transport and may be significant in large trees.
What is the Mechanism of Polar Auxin Transport
The auxin indole-3-acetic acid (IAA) enters the cell by passive diffusion in a protonated (IAAH) form and/or by secondary active co-transport in its anionic form (IAA-), via influx carrier (AUX1 protein). The anionic for (IAA-) predominates in the cytosol, which has a neutral pH. The anions exit the cells only at the basal end, via efflux carriers (PIN proteins).
Explain Auxin transport through the root
The formation of lateral roots is dependent on both acropetal (from base to tip) and basipetal (from tip to base) transport of auxin in the parent root.
Most auxin reaching the root tip is transported acropetally and nonpolarly in the sieve tubes of the ploem. At the root tip, the auxin is redirected to teh basal part of the root (basipetal polar transport).
The priming of pericycle cells as lateral root founder cells is belived to occure in the basal half of the apical meristem.
Lateral root initiation is dependent on auxin from the root tip, and emergence of the lateral root requires auxin from the shoot.
What is the major function of auxin in coordination plant growth and development
1. Promotes cell elongation - mediated via the acid-growth hypothesis (shoot and root)
2. Maintains apical dominance
3. Regulates root growth
4. Promotes fruit growth
Explain the chemical nature, site of biosynthesis, transport, and effects of the hormone Cytokinins
Chemical nature: Are N6-adenine derivatives, phenyl urea compounds, Zeatin is the most common cytokinin in plants
SIte of Biosynthesis: Primarily in root tips
Transport: Transported in the xylem from roots to shoots
Effects: Promotion of cell division; promotion of shoot formation in tissue culture; delay of leaf senescence; application of cytokinin can cause release of lateral buds from apical dominance and can increase root development in arid conditions.
Explain the Acid-growth hypothesis of Auxin for cell elongation
1. IAA stimulates a mebrane-bound protein that pumps proteins (H+) into the cell wall using ATP
2. The accumulation of H+ ions in the wall stimulates enzymes called 'Expansins' that cause cellulose microfibrils to relax and water flows into the cell and then into the vacuole
3. Exerts a turgor pressure that causes cell expansion
Explain Apical dominance
Implies dominance of teh apical region of a shoot over the growth of the axillary buds.
What does Auxin have to do with fruit walls?
AUxin produced by the developing embryo induces maturation of teh ovary wall and teh development of the fleshy fruit.
What is meant by the term Parethenocarpy?
Auxin induces the formation of fruit without pollination (no seeds).
Apical Dominance of Cytokinins
They can overcome the inhibiting effect of auxin on axillary bud growth.
What is Kinetin in relation to Cytokinins
A substance that does not naturally occure in a plant. BUt have involvement in cytokinesis (cell division)
What is Zeatin in relation to Cytokinins
A Naturally occurring cytokinin
Explain differentiation of tissue cultue of Cytokinins in association with auxin.
Tissue culture- teh maintenence of plant segments (explants) on defined media.
- Agar -for solid support
-SUcrose
-NIrtients
Explain the Ratio of Cytokinins and Auxins
Intermediate ratio: Callus is formed
Low Auxin to cytokinin ratio: Shoot formation
High Auxin to cytokinin ratio: Root formation
Explain the chemical nature, site of biosynthesis, transport, and effects of the hormone Gibberelins
Chemical Nature: (GA2), a fungal product, is most widely studied. GIbberallins are synthesized via the terpenoid pathway
Site of Biosynthesis: IN the young tissues of the shoot and developing seeds. It is uncertain whether synthesis also occurs in roots.
Transport: Are transported in the xylem and phloem
Effects: Hyper elongation of shoots by stimulating both cell division and cell elongation, producing tall, as opposed to dwarf, plants; induction of seed germination; stimulation of flowing in long-day plants and biennials; regulation of production of seed enzymes in cereals.
Explain how GIbberellins promote seed germination.
GA3 produced by the embryo migrates to into the aleurone layer, stimulating the synthesis of hydrolytic enzymes. these enzymes are released into the starchy endosperm, where they break down the endosperm reserves into sugars and amino acids, which are soluable and diffusable. the sugars and amino acids are then absorbed into the scutellum (cotyledon) and transported to the shoot and root fro growth
Explain the chemical nature, site of biosynthesis, transport, and effects of the hormone Ethylene
Chemical Nature: The gas ethylene(C2H4) is synthesized from methionine. It is the only hydocarbon with a pronounced effect on the plant.
Site of Biosynthesis: IN most tissues in response to stress, especially in tissues undergoing senescence or ripening.
Transport: Ethylene, a gas, moves by diffusion from it's site of synthesis
Effects: Fruit ripening (especially in climatic fruits, such as apples, bananas, and avocados); leaf and flower senescence; leaf and fruit abscission.
What is senescence
Aging, deterioration.
Explain the chemical nature, site of biosynthesis, transport, and effects of the hormone Abscisic Acid
Chemical Nature: Synthesised from a Carotenoid intermediate. the name is a misomer because the hormone has little to do with abscission.
Site of Biosynthesis: In mature leaves and roots, especially in response to water stress. MAy e synthesized in seeds.
Transport: Is exported from leaves in the phloem; from roots in the xylem.
Effects: Stomatal closure; induction of photosynthate transport from leaves to developing seeds; induction of storage-protein synthesis in seeds; embryogenisis; may affect induuction and maintenance or dormancy in seeds and buds of certain species.
Explain the chemical nature, site of biosynthesis, transport, and effects of the hormone Brassinosteroids
Chemical Nature: Are polyhydroxylated steroid compounds, synthesized as a branch of the terenoid pathway.
Site of Biosynthesis: throughout the plant, especially in young growing tissues.
Transport: Endogenous brassionsteroids act locally, at or near their site of synthesis.
Effects: A wide range of developmental and physiological processes, including cell division and cell expansion; branching; vascular tissue differentiation; development of lateral roots; seed germination; leaf senescence.
What are three external environmental cues for certain growth in a plant?
Light, Gravity, Temperature
What is Phototropism in a plant?
The plant bends towards or away from the light
What is Photoperiodism?
Response to the relative periods of light and dark, i.e. the day length
What is Photomorphogenesis
Effect of light on the form (development) of the plant.
What are the three stages in the activation of cellular process?
1: Reception - Hormones attach to receptor area.
2: Tranduction - Reactions producing, second messenger.
3. INduction - Activation of cellular processes.
What is the difference between negative and positive phototropism?
Negative Phototropism - Growth response away from the light
Positive Phototropism - A growth response towards towards the light.
Explain phototropism and its growth in response to light.
Perception of light by a blue light responsive proteinaceous photoreceptor called cryptochrome
Transduction is not known
Growth response in phototropism mediated by a redistribution of auxin.
Explain Photoperiodism
Cues that are given by the relative lengths of the day and night
What are some photoperiod effects
Induction of bud dormancy i perennial plants, and the timing of flowers
Explain bud dormancy
The survival mechanism. New shoots form the next seasonal growth, day length is the cue to the onset of bud dormancy -phototperiod response.
Initiated jsut after midsummer.
Dormant buds are inclosed by bud scales
The scales halp prevent desiccation, restrict movement of oxygen into the bud, and insulate the bud from heat loss.
Explain teh difference between short day and longday plants and their link to photoperiodism and flowing.
Short day: These flowers only if the light periods are shorter than a critical length,
-tend to flowers in spring or Autumn e.g. strawberries
Long day plants: These flower only if the light periods are Lnger than a critical length.
- tend to flower in summer
What is the chemical basis of photoperiodism?
The photoreceptor involved in photoperidosm is a proteinaceous pigment called Phytochrome.
- Present in all vascular plants
-exists in two interconvertable forms
+ a red light absorbing form (Pr)
+ a far-red light absorbing form (Pfr)
-in normal daylight there is more red light than far-red light so Pfr (the biologically active form) will predominate
-at night Pfr reverts back to Pr
Describe the phytochrome
There is two identical subuinits, they have two bunny ears and then two spherical bottoms. The chromophore is at the top of the oval bunny ears and the photoreceptor activity happens half way down. Kinase activity happens at the spherical ends.
Explain phytochrome switching
The two bunny ears of the phytochrome are a distance away it is in Pr light absorbing form (660 nano meters). When it absorbs red light is changes and the chromophore come closer together (bunny ears). The phytochrome is now in the Pfr light absorbing form and now has biological responses, breakdown of products. It will revert back with far Pfr light (730) or with long dark periods.
Which plant organ perceives the daylength?
Site of perception in in the leaves (via phytochrome) but the response occure in the floral buds.
What happens within the signal of florigen
Perception of the signal then triggers the conversion of the vegetative apex to a floral apex, hormones are involved, particular the gibberellins for Long day plants.
What is photomorphogenesis
the effects of light on plant morphology. Responses to light are different than responses to chemical signal in that there is no real signal molecule
What is a cryptochrome?
Opposite of a phytochrome where instead of red light and fer red, the cryptochrome perceives blue light to determine the direction of the light.
what are the light requirements for germination?
Seeds only germinate when close to the oil surface. they only hve limited reserves to fuel the growth of the plant from shoot/coleoptile until it breaks the soil surface and the leaves to begin photosynthesis.
Red light stimulates germination in some seeds, far red inhibits germination of some seeds.
What does blue light do to IAA (Auxin)
Causes the IAA to move to the shaded side of the plant to promote elongation and thus bending
What is Heliotropism?
It is a variation of phtototropism.
-Leaf lamina and apical buds respond to the changes in direction of sun rays, tracking the sun during the day.
-Sunflowers are classic examples as are flower heads and apical shoots of apples
-Flowers and leaves return from dusk westerly to dawn easterly inclination.
What is Gravitropism?
Growth of a plant in response to gravity
- Roots grow downwards (positive gravitropism)
- Shoots grow upwards (negative gravitropism).
How does the plant perceive gravity?
Must involve movement of some entity i sensitive cells.
In the root:
-the root cap perceives perceives this signal
- Gravity is correlated with sedimentation of amyloplasts or statoliths, mobile grains that redistribute in the cell.
- Dissaperence of statoliths from theroots cap also leads to loss of response to gravity
- Nature of signal in shoot tip is not known.
What is signal transduction and transmittance in relation to the perception of gravity
Primary event in transduction is not known, but it probably involves differential pressure caused by statoliths.
redistribution of C++ ions and auxin appear to be involves
Any asymmetry established leads to Ca++ and IAA to lower side of root cap
IAA moves acropetally to lower side of elongation zone where supra optimal concentration inhibits growth leading to downward curvature. Higher IAA concentration on lower side than upper.
What is Thigmotropism?
PLant response to contact with a solid object e.g. tendrils that grasp a solid object.
(Direction of curvature responds to direction of touch, cells on non-stimulated side of tendril elongate more rapidly than cells on contact side. Response occurs within seconds of contact and mediated by jasmonic acid
Tendrils detect contact via sensory epidermal cells calle 'tactile blebs', rich in microtubles and actin filaments).
Explain Thigomorphogenesis
-Developmental plant responses to touch can be marked.
-Rubbing or shaking plants result in slow stem elongation, increased growth of girthdiameter.
-Wind causes growth retardation by 40-60% but results in shorter, stronger plants less easily damaged by mechanical stress.
-Spraying plants in glasshouse with waterr for 10 seconds a day reduce growth by 40%
-PGR' such as auxin, ABA, ethylene probably involved in response.
What is Nastic responses?
#NAME?
Explain Nyctinasty
Leaves change from horizontal during the day to nearly vertical at night. Caused by rapid, reversable water movement into and out of special motor cells in teh petioles. Water movement occurrs in response to osmotic driving force of ion (K+) transport, similar to stomate opening and closin.
What is Thigmonasty
Nastic movement resulting from touch
What is Hydronasty
Folding or rollig of leaves in response to water stress. Supplements closure of stomates to reduce transpiration
Explain Circadian rhythms
Plant undergo dinural rhythms and thse continue even when plant is placed in continuous light. The rythems are endogenous and are the plants biological clock.
What is the purpose of the Circadian rhythem?
Coordinates daily events in plants, enables plants to respond to seasons by accurately measuring day length.
What are some rhythmic phenomena observed under the Circadian moment in plants?
Petal movement; growth rates of various organs; concentrations of pigments and hormones; stomatal opening and closing; discharge or fragrance from flowers; times of cell division; metabolic activities, volume of nucleus.
What are the affects of temperature in the response within the plant?
#NAME?
What are some of the negative affects to a plant in chilling temperatures?
Tropical and subtropical fruits and vegetables are damaged when temperatures are less than 10-14 degrees centigrade.
Normal products are very perishable
Problems for storage and transport to market
Symptoms: pitting, internal browning, water soaking, cellular damage, cell collapse and invasion by fungi leads to rot.
What happens to plants in high temperatures?
Plants have protective mechanisms for exposure to high temperatures
Produce heat shcock proteins that ensure basic metabolism occures
Genes controlling many less important metabolic events are down regulated
High temps for relatively short periods of time used for dis infestation and extension of storage life for some horticultural crops.
Explain the benefits of Winter chilling for plants.
Cold temps are required in many plants species to break dormancy. Many temperate deciduous fruit trees, such as peaches, apples, kiwifruit need chilling.
Warm winters result in weak, sporadic and uneven budbreak, and hence poor crops in some years.
What hardiness development?
As daylength decreases, plants undergo numerous physica, physiological and metabolic changes in preparation for winter.
Cold acclimation development of cold hardiness.
this is the strata in which the plant survives etreme cold and dehydration effects of winter
Occurs in both deciduous and evergreen species including NZ native species.
What are the practical implications in protection against frost damage
- Many plants are susceptible to frost damage in teh srpinf and autumn
-This may limit the production in some climatic zones
-Methods available reduce chances of frost damage to buds, blossom and new shoots.
-Adding heat with frost pots; water sprinkling using latent heat fusion; helicopters or wind machines to use warmer inversin layer air temperatures; use of protected covers such as greenhouse or plastic covers.
Explain seed dormancy in response to low temperatures
#NAME?
What is Stratification?
Prechilling, exposing seeds to cool, moist conditions, often in sand, for up to 100 days ad 5 degrees Celsius.
-Seeds must be imbibed (to rehydrate the seed) before they will respond to cool temperatures
- GA can often replace the chillig requirment.
Explain flowing in response to low temperature
- Some plants must be exposed to cold temperatures before they will flower e.g. winter wheat.
-This process is vernalisation = low temperature promotion of flowering; effective temperature 6 degrees Celsius (different from stratification which is the cold requirment for seed germination).
-Cold signal perceived in apex; sometimes it can be replaced by GA
-Often photo periodic requirements must be satisfied once cold requirement is met.
Give plant examples of Plant Vernalisation
Winter wheat:
-Vernilisation (meristem)
Cold Moistened mature seed (absolute requirement)
plus
-Photoperiodism (leaves and buds)
LOng days, leaves of younf plant perceive light signal
How are flowers initiated? (1)
Transition from vegetative growth to reproductive development in seed plant. Involves fundamental changes in the shoot apex that results in the appearance of the flower or inflorescence primordia.
Shoot apex must be competent to respond to appropriate endogenous or external signal.
Massive morphological changes in meristem as it changes from vegetative to floral.
What are the pathways to flowering?
Vernalisation pathway:
-low temperature induction; hi-cane in kiwifruit overcomes lack of winter chilling.
Photoperiodic pathway:
-effect of daylength and wavelength (red and far red) of light
Gibberellin pathway: induces bolting in biennial plants
Autonomous pathway: responds to endogenous cues as yet unknown.
What is a fruit set and how does it develop?
Fruit: Tissue that supports the ovules of a plant and whose development is dependent on psychological changes occurring in those ovules.
Fruits may be derived from many different tissues.
Three stages of fruit development:
1. Pollination
2. fertilization
3. fruit and seed development
Explain fruit pollination
Stimulates development of an ovary into a mature fruit.
-Pollen is excellent source of auxin, cytokinins that probably initiates fruit growth. After pollination, ovary produces auxin, cytokinins
- Accompanying fruit development, pollen produces ACC that moves to other floral parts (petal, sepals), forms C2H4 that induces abscission.
Explain fruit and seed development.
-Ovary, receptacle, sometimes parts of the floral tube may be the basic tissues from which the fruit is derived
-Following pollination there is an intense period of cell division (6-8 weeks for apple) coincides with high cytokinin concentrations
-Synthetic cytokinin, CPPU, sprayed after bloom increases fruit size
-This is followed by fruit expantion growth caused by cell enlargement promoted by auxin produced in seeds.
-Both auxins and gibberellins are involved in controlling cell growth during fruit develompent
What is Parthenocarpy
Fruit that develops without pollination, occurs naturally in bananas, pineapples and some tomatoes
Explain the source sink relationship for fruits and seeds
Seeds an developing fruits have massive requirements to sustain growth; hence they are are strong sink for carbohydrates and nurtients.
Results in distribution of energy from source to sinks
-mobilisation of photoassimilates from leaves and sometimes from woody tissues
- large transport of C and N containing compounds into fruitlets and/or seeds.
Developing fruits/seeds produce PGR's that interact to create a powerful sink; leaf sources can increase rate of activity to remain in homeostasis
As leaves develop they change from being ne IMPORTERS of assimilates t net EXPORTERS
Later in development proteins accumulate in seeds.
What is the Harvest Index?
The ratio of harvested biomass to total shoot or total plant biomass
Explain the manipulations of Souce/Sink
- Dawarfing rootstocks and pruning managment in fruit trees
-Girdling; NAA to prevent shoot growth after summer pruning
-Growth retardents affect source/sink
-Synthetic anti-gibberellin compounds most widely used
+ Cycocel (CCC) used to create dwarf wheat in North EUrope
+ Triazoles such as Paclobutrazol
-If less assimilates used in stem growth, then carbon can be diverted to grain or fruit
+ increase yeild in wheat
+ increase flowing and fruit set in cherries
+ increased DM, fruit size in kiwifruit.
What happens to a tree when you cut a wide girdle in it?
Kills the tree
What happens whe you double gridle a tree?
Increased fruit size, dry matter and return blossom in kiwifruit.
What are the mechanisms for dormancy?
Imposed by either seed coats/embryo covers. Or the state of embryo dormancy.
Explain seed coat induced dormancy
Impermeability of seed coats to water; coats of such hard seeds must be scarified before they can imbibe water and germinate.
Impermeability of coats to gases: prevent ingress of oxygen required for germination
Mechanical resistance to embryo growth: In tomato a special enzyme, mannase , must be activated to digest layers of endosperm
Explain Embryo induced Dormancy
Cuased by metabolic block in process leading to germination
Immaturity of embryo: Needs time to mature properly. Needs to imbibe at low temperature (<5 degrees C) during winter to mature then further low temp (stratafacation) to break dormancy.
Requirement for dry storage: Prevents germination in plant or prior to dry season (after-ripening). Wild oats good example; mechanisms unknown.
Show the examples of light treatment on the quality affect on germination.
R= Red Light, FR = Far red.
Light treatment: %Germination:
None 8.5%
R 98.0%
R + FR 54.0%
R + FR + R 100%
R + FR + R + FR 43.0%
R + FR = R = FR + R 99.0%
Does order of red and far red light illumination affect seed germination?
Red light stimulates, Far red light inhibits seed germination. Final light exposure determining factor. Effects of RED and FR light is reversible.
Describe the Germination action spectra
Action spectra for light controlled germination matches the absorption spectra for red and far red light (peak activity 660nm and 730nm respectively).
How does the Phytochrome affect seed germination?
Germination stimulated by Pr, while germination is ihibited by Pr
What is PGR affect on Germination
ABA blocks promotive reaction of red light inhibiting germination; GA active replaces light requirement and promotes germination.
What are the requirments for chilling?
Seeds require a period of low temperature chilling after imbibition (<5C) so as to germinte.
Chilling or stratiication reduces inhibitos (ABA) and increases promoteors (GA, cytokinins) of seed germination.
GA can replace chilling in some seeds.
How does ABA relate to seed dormancy?
Increase during late seed development
-Stimulates seed protein production
- prevents premature germination
Breaking of seed dormancy associated with declining ABA
Seeds fromABA deficient mutants do not become dormant
-Sprout on plant
-are viviparous
How does Gibberellins releate to germination?
GA induce hydrolytic enzymes such as alpha-amylase, in germinating cereal seed
Early seedling growth is dependent on substrates stored in the seed (e.g. starch in endosperm) being metabolized to solute, mobile compounds
Seeds from mutants lacking GA will not germinate
Why is the Scutellum in a grain seed useful
Specialized for the absorption of the endosperm
Explain the Ethylene triple response
Enables emerging seedlings to avoid obstacles
Observed by Neljubov 1901 while studying effects of illuminating gas on Pea seedlings
- Decreased longitudinal growth
- Increased radial expansion in epicotyl and roots
-Horizontal growth
Ethylene produced in response to contact with shoot tip.
Explain starch storing seeds
Starch degraded by amylase to soluble sugars
GA3 stimulated germination or dormant barley seeds
Gibberellins promote expression of the gene coding for Alpha amylase
ABA inhibits germination of barely seeds
ABA inhibts transcription of the gene for Alpha amylase
Soluble sugars are absorbed by scutellum, transported to the embryo where they are utilized for germination and growth
Storage proetin degraded by proteases to amino acids
Mobile amino acids pass to embryo
Reconstituted into enzymes and other proteins used for germination and growth.
What are the three plant growth phases
1. Juvenile: Unable to flower
2. Adult Phase: Vegatative but able to respond to appropriate environment cues.
3. Reproductive phase
What is heteroblasty?
Leaves produced by juvenile phase of apical meristem.
What is Senescence
THe process of deterioration that accompanies aging and leads to the death of an organ or organism. Affects all plant parts and is coordinated, controlled developmental event in the life cycle of plants
WHat is the biological reasons for Senescence?
Annuals: Recovery of nutrients from senescing organs represents conservation of resources to plant.
Simultaneous senescence: reserve compounds, Carbon and Nitrogen compounds and nutrients are transported from leaves to stem for storage
-Reduction in transpiration
-leaf litter -recycling
Sequential senescence: Upper leaves remain green and functional while lower leaves become parasitic for a while, then senesce releasing nutrients for recycling and abscise.
How is Senescence programmed?
Specific genes are both down regulated and up-regulated indicating orderly event.
Activation and synthesis of genes for degradative enzymes to hydrolyse carbohydrates to soluble sugars, and proteins to amino acids.
Transported in active, energy requiring processes to fruits/seeds, stems/branches, trunks and roots for storage. Mitochondria remain active.
Early autumn frost can kill leaves before this process complete depriving plant of it's reserves.
How does leaf senescence affect the autumn colors?
#NAME?
How does Cytokinins play a role in modulating leaf senescence?
#NAME?
How does Ethylene induce senescence?
Fruits: Application of C2H4:
-Sensitivity increases during maturation
-triggeres rapid and uniform ripening
-induces abscission
Flowers: INduces fading, withering, and abscission of petals
Leaves: INduces loss of chlorophyll, RNA and protein; outward transport of nutrients; abscission.
What are Ethylene inhibitors?
They delay C2H4 biosynthesis and action inhibits/delays fruit ripening, flower and leaf senescence.
How does Ethylene cause abscission?
-C2H4 induces hydrolytic enzymes, cellulase, pectinase, that initiate the separation process in abscission layer.
-Abscission induced bt exogenous C2H4 or by C2H4 producers (Ethephon)
- Leaves of different ages vary in sensitivity to C2H4 gas.
Explain the process of fruit ripening.
Softening:
-Hydrolysis of pectins in middle lamina
-induction of hydrolytic enzymes to break down xyloglucans
-disassembly of cell wall gives texture change
Hydrolysis of starch to sugar, coincides with softening in kiwifruit
Decrease in astringent phenolics
Change in pigment composition; loss of chlorophyll; synthesis or red pigment lycopene
Changes in respiration and C2H4 production.
Describe the difference between Climacteric and nonclimacteric fruit.
Climacteric fruit:
-Will ripen after harvest; C2H4 will induce ripening; quality improves after harvest
-,marked respiration increase to a peak then decline postharvest
-autocatalytic C2H2 production postharvest
-e.g. apples, tomatos, bananas
Nonclimacteric fruit:
-fruit ready to eat at harvest; will not improve in quality; e.g. citrus, cherries, pineapple
- no increase in respiration postharvest
-no autocatalytic C2H4 production
What is Postharvest physiology
Study to understanding and controlling factors affecting the product quality after harvest including:
-preharvest factors such as nutrition (Ca, N, P), irrigation, plant management.
-Optimizing harvest maturity
-Manipulating biosynthesis and action of C2H4
-Atmosphere manipulation to minimize respiration and C2H2 production
-texture, flavor and consumer acceptance
-transgenic to influence deterioration rate.
What is the point of Ethylene manipulation?
-Prevent contamination with hygiene
-Reduce biosynthesis with AVG (Retain) or controlled atmospheres
-Reduce action with Ag ions, CO2, or MCP
-Genetics: Breed plants with low C2H4 production or low sensitivity; transgenics with little or no ACS or ACO or with modified receptor have delayed or inhibited ripening.
Why is Mineral nutrition important in plants?
Deficiencies or excess in some major elements decrease postharvest quality
-excess nitrogen causes premature softening
-deciciency of calcium widespread in NZ
+ leads to many serious disorders such as bitter pit in apples and blossom end rot in tomatoes
+ Increases softness through cell wall affects preharvest sprays and postharvest dips used to enhance calcium in fruit.
What is the basis of important postharvest technology?
- Sugar + Oxygen <---> Carbon Dioxide + H2O + Heat
-reduce RR by decreasing temperature, reducing oxygen or by increasing CO2 in surrounding atmophhere.
-Reaction is exothermic giving off energy in teh form of heat
- No free water released; it becomes bound metabolically
-Reduced RR associated with decreased C2H4 production and subsequent reduce rate of quality deterioration.
Why are postharvest fruits stored at low temperatures?
#NAME?
Explain why a modified atmosphere is important for fruit storage?
-Normal atmosphere of 21% O2; 79% N2 is modified in a controlled or passive way
-MA normally is polymeric film bags with specific gas transmission proterties; gas varies depending on temperature and respriation
-O2 decreases and CO2 increases (both by respiration) reduces respiration which in turn reduces C2H2 and deterioration rate
SOme higly specific films now available that change permeability as temperature changes thus avoiding anaerobic conditions.
How is the atmosphere controlled for fruit storage?
-DOne in sealed rooms with sophisticated gas sensors linked to computers for fine controles
-Major crops stored in CA (controlled atmosphere) are apples, pears, kiwifruit, cabbages.
-O2 reduced to 1-3%; CO2 sometimes used ar 1-8%; remainder N2
-Excess C2H4 and CO2 removed with special scrubbers; KMnO4 and/or activated charcoal respectively.
Give the Hierarchical Plant classification in an example
Kingdom - Plantae
Division - Tracheophyta
Class - Magnoliopsida
Order - Myrtales
Family - Myrtaceae
Genus - Metrosideros
Species - Excelsa
Explain the term 'Life Cycle
Entire sequence of phases in the growth and development of an organism from teh formation of a zygote to the formation of a gamete
Explain the process of Zygotic Meiosis
The zygote divides by Meiosis to form four haploid cells. Each of these cells divides by mitosis to produce either more haploid cells or a multicellular haploid individual that eventually gives rise to gametes by differentiation.
Explain the process of Gametic Meiosis
The haploid gametes are frmed by meiosis in a diploid individual and fuse to form a diploid zygote that divides to produce another diploid individual
Explain the process of Sporic meiosis, or Alternation of Generations?
The sporophyte or diploid individual, produces haploid spores as a result of meiosis. These spores do not function as gametes but undergo nitotic division. This gives rise to multicellular haploid indiviuals (gametophytes), which eventually produce gametes that fuse to form diploid zygotes. these zygotes in turn, differenciate into diploid individuals.
What is a gametophyte and is it Haploid or Diploid?
#NAME?
What is a sporophyte and is it Haploid or Diploid
-Diploid (2n)
-Spore-producing generation
Describe the difference between haploid and diploid.
Haploid:
- Having only one set of chromosomes (n)
-Characteristic of gametophyte generation
Diploid:
-having two sets of chromosomes (2n)
-characteristic of sporophyte generation
Describe the difference between Gamete and Spore
Gamete:
-Reproductive cell
-Always haploid (n)
- fuses in paires to form a zygote (2n)
Spore:
-reproductive cell
-usually haploid and unicellular
-capable to develop into adult without fusion with another cell.
Describe the difference between Mitosis and Meiosis
Mitosis:
-Nuclear division forming two identical daughter cells
Meiosis:
- two successive nuclear divisions in which the chromosome number is reduced from diploid (2n) to haploid (n)
What are the three important algae groups and their photosynthetic pigments
Brown Algae: Phaeophyta
-Pigment: Chlorophyll a and c; carotenoids, mainly fucoxanthin
Red Algea: Rhodophyta
- Chlorophyll a; phycobilins; carotenoids
Green Algae: Chlorophyta
- Chlorophyll a and b; carotenoids
What algae are used as a food source, why they are used?
#NAME?
Explain Chlorophyta (Green Algae) and it asexual and sexual reproduction.
-Fresh water algae
-Unicellular, motile (2 flagella)
-Haploid phase dominant -zygote is the only diplod cell
-Asexual reproduction:
+haploid cells divide by mitosis
-Sexual reproduction
+ gametes of different mating types (+ and -) fuse and form diplod zygote.