what is a meristem
region of undifferentiated, totipotent parenchyma cells that divide and give rise to other cells
what are the types of meristematic regions
1. apical meristems
2. primary meristems
3. vascular cambium
4. phellogen
what are the two types of meristematic cells
1. intials
2. derivatives
what is an initial
the function is to divifde but it does not differentiate and stays part of the meristem
what is the derivative
following cytokinesis it differentiates and becomes part of the cell
how do cells differentiate
-responds to chemical or environnmental signals
what is primary growth
-elongation
-traced back to apical meristem which is the meristem at the tip of ROOT or STEM
what is the apical meristem
it is the meristem at the tip of the ROOT or STEM and it gives rise to primary meristems which give rise to primary tissue systems
what is the protoderm
a primary meristem that comes from the apical meristem and leads to the dermal tissue
what is the ground meristem
a primary meristem from the apical meristem and leads to ground tissue
what is the procambium
a primary tissue from the apical meristem and leads to vascular tissue
what is significant about primary growth in the root
-it is divided into 4 zones
what is secondary growth
-increase in girth in ROOT or STEM
-it can be traced back to the vascular cambium or phellogen
what is the vascular cambium
it is a layer of meristematic cells between the phloem and xylem which produces secondary xylem and phloem
what is secondary xylem
wood; it accumulates
what is secondary phloem
-bark is made of secondary phloem and periderm
-seive tube members are only active for a short time thus old layers of phloem die and are sloughed off
what is the function roots
they anchor the plant, absorb and conduct water, and control movement of water and ions, they store starch and detect gravity
what are the 4 zones of the root
1. rootcap
2. region of cell division
3. region of elongation
4. region of maturation
what is the root cap
it is a mass of short lived parenchyma cells that cover the tip of the root; it secretes mucigel, protect the apical meristem, and orients plant growth
what is the zone of division
it is the location of the apical meristem behind the rootcap; it does cytokinesis
what is the zone of elongation
region where derivatives of the meristem elongate
what is the zone of maturation
where cells differentiate. it has ROOOOT HAIRS
what are the three tissue systems in roots
1. epidermis (dermal)
2. cortex (ground tissue)
3. vascular cylinder (vascular tissue)
what does the epidermis do
absorbs water and minerals; it has a thin cuticle for absorption and root hairs to increase surface area
what is the cortex
it is the ground tissue in the root; amyloplasts help with storage; intercellular spaces help with circulation of atmosphere; and the endodermis controls water into the vascular cylinder
how does water move in the roots
1. apoplastic; thru intercellular spaces
2. symplastic: from cell to cell thru the plasmadesmota
3. transcellular: thru vacuoles, membranes and walls
what is the endodermis
innermost layer of the cortex; it is densly packed parenchyma cells with casparian strips made of suberin and it controls water flow into the vascular cylinder
what is the vascular cylinder and what are the 3 regions
it is vascular tissue made of the pericycle, primary phloem, and primary xylem
what is the pericycle
outermost layer of vascular cylinder, gives rise to lateral roots, contributes to vascular cambium, and periderm
what are lateral roots
branch roots; endogenous formation bc they form in the pericycle and PUNCH OUT
what is the taproot system
primary root that is long lived and grows deep but secondary growth is common; found in gymnosperms and dicots
what is the fibrous root system
it is primary short lived made up of adventitious roots and lateral roots; shallow and no secondary growth
what are adventitious roots
roots that grow from an organ other than another root; ie a prop root
ariel roots
from epiphyte plants which grow on other plants but are not parasitic; they may absorb water or be photosynthetic
velamin
a type of multiple epidermis that provides mechanical strength and protection from loss of water
haustorium (hostile)
modified root of parasitic plants; parasitic plants lack photosynthesis
what is the stem
the main axis of the plant; origin of new stems and leaves, support, conduction, storage of starches and water
what is a shoot
stem with associated leaves and buds
what is a node
point of the stem at which leaves attachc
what is the internode
region of the stem between two adjacent nodes
what is the structure of the apical meristem
1. the tunica is the outercovering and gives rise to the epidermis
-the corpus is the inner layers and gives rise to ground tissue and vascular bundles
what are buds
embryonic shoots; there are terminal buds and axilary buds (grows into branches and flowers)
what is the stem structure in a dicot
has a pith in center and vascular bundles in a circle
what is the structure of monocot stem
no pith and vascular bundles scattered
what is the vascular bundle structure
phloem on outside and xylem on inside; in the stem it is associated with fibers (bundle sheath)
what is the rhizome stem
horizontal and underground stem
what is the tuber stem
an enlarged part of underground storage stem with buds that extend out to form new plants (e.g. potato)
what is the bulb stem
short underground stem with leaves (onion)
what is the succulent stem
a stem modified for water storage and is often phoyosynthetic due to lack of leaves
what is the tendril stem
a stem that supports thee organ by twisting around another structure; found in some vines
what is a thorn
a modified stem
what is urushiol
in posion ivy
what type of root is adventagious
a nonconducting root, it is not in the ground
what does the vascular cambium yield
secondary phloem and seconday xylem
what does phellogen yield
the periderm
what are the two cell types of the vascular cambium
1. fusiform initials (produce the axial system with vessel elements)
2. ray intials (give rise to rays in phloem and xylem)
what is the axial system
a wood tissue that creats secondary xylem and secondary phloem that contains vertical axes which originate from fusiform intials so they have vessel elements
what is the radial system
a wood tissue with horizontal rays from the ray initialss which moves food
gymnosperm
simple axial sysstem that lacks vesssels. ie conifers, pine trees
angiosperm
complex axial system ie flowering plant trees and shrubs
sapwood
in a woody stem, the layer of secondary xylem that surrounds the heartwood; usually active in fluid transport
heartwood
nonfunctional wood that has ceased growing
what is outer bark
periderm layer that is DEAD
what is inner bark
phloem tissue that is LIVING
what is periderm
secondary tissue that replaces the cortex and epidermis; from phellogen and turns to outer bark; allows for gas exchange because its dead
how does the periderm allow for gas exchange
because of the lenticels which are intercellular spaces that allow for gas to reach the secondary phloem or the inner bark
what are the three tissue systems in leaves
1. epidermis (dermal tissue)
2. mesophyll (photosynthetic ground tissue)
3. veins (vascular tissue)
what is the upper epidermis
in leaves, it has a thicker cuticle and no stomota for UV protection and to protect dessification
what is the lower epidermis
in leaves, it has a thinner cuticle and abundant stomota to allow for gas exchange
what is palisade parenchyma
the upper half of the mesophyll; column shaped cells densly packed with cholorplasts and small intercellular spaces
what is spongy parenchyma
it is the lower half of the mesophyll; irregularly shaped cells with HUGE spaces to allow for gas exchange because it is tied to the presence of the lower epidermis
what is the bundle sheath in leafs
it surrounds the veins and is made of parenchyma cells which controls water loss and serves as a boundary
what are the two main plant adaptations
1. aquatic (thin cuticle and stomota on UE)
2. xerophytic (thick cuticle)
pinnate and palmate are found in......
dicots
parrallel venation is found in....
monocots
spines are....
modified leaves; thorns are modified stems