what are xerophytes?
plants living in dry habitats, adapted to lose as little water as possible
what are some examples of xerophytes?
cacti, madam grass
what are some adaptations of xerophytes?
> thick waxy cuticle (cacti &maram grass) > sunken stomata (maram grass) > reduced numbers of stomata > reduced SA of leaves (cacti) > microhairs on leaves (maram grass) > curled leaves (maram grass) > succulents > leaf loss > long tap roots > widespread roots > closing stomata (cacti)
how does having sunken stomata allow xerophytes to reduce water loss?
stomata are small pits which trap moist air, preventing wind from increasing the water potential gradient and therefore reducing transpiration rates
how does having a thick waxy cuticle allow xerophytes to reduce water loss?
the waxy cuticle is waterproof, so reduces water loss by evaporation
how does having a reduced number of stomata allow xerophytes to reduce water loss?
having less stomata means there will be a decreased amount of gas exchange and therefore decreased transpiration
how does having leaves with a reduced SA allow xerophytes to reduce water loss?
as leaves decrease in SA e.g becoming needles in the case of cacti, there is less stomata and therefore less water lost through transpiration
how does having microhairs on leaves allow xerophytes to reduce water loss?
microhairs trap humid air, reducing the water potential gradient and therefore the rate of transpiration
how does having curled leaves allow xerophytes to reduce water loss?
curled leaves confine stomata within a humid environment, reducing the water potential gradient and therefore reducing transpiration
how does leaf loss allow xerophytes to reduce water loss?
losing leaves stops water from leaving stomata altogether, preventing transpiration
how does having long tap roots allow xerophytes to reduce water loss?
long tap roots are found very deep into the soil, accessing water way below the surface which can benefit the xerophytes especially during a drought
how does having widespread roots allow xerophytes to reduce water loss?
widespread roots have a high surface area, maximising water uptake from rain before this evaporates
how does having closing stomata allow xerophytes to reduce water loss?
closing stomata allow xerophytes to have reduced rates of transpiration due to their ability to close during very hot days, when transpiration rates are high
how are cacti adapted to their environment?
these have a thick waxy cuticle, small, thin needles instead of leaves and closing stomata to prevent water loss as effectively as possible
how is maram grass adapted to its environment?
this has a thick waxy cuticle, sunken stomata, microhairs on its leaves and also curled leaves to reduce transpiration rates as much as possible
what are hydrophytes?
plants living in aquatic habitats, adapted to live in water and cope with low oxygen levels
what is an example of a hydrophyte?
waterlilies
what are some adaptations of hydrophytes?
> very thin/no waxy cuticle > always open stomata on upper surfaces > reduced structure & increased flexibility (waterlilies) > wide, flat leaves > small roots > airspaces in tissues
how does having a very thin/no waxy cuticle benefit hydrophytes in living in an aquatic environment?
having a thin waxy cuticle means water does not need to be conserved
how does having always open stomata on upper surfaces benefit hydrophytes in living in an aquatic environment?
the stomata maximise gaseous exchange for the hydrophyte through the leaves floating above the water, which is essential as this must live in an environment with low oxygen levels whilst also requiring oxygen for cellular respiration
how does having a reduced structure and increased flexibility benefit hydrophytes in living in an aquatic environment?
hydrophytes do not require a rigid structure as these are simply supported by the water they are submerged in, and are flexible to prevent damaged caused by water currents
how does having wide, flat leaves benefit hydrophytes in living in an aquatic environment?
these maximise the uptake of sunlight
how does having small roots benefit hydrophytes in living in an aquatic environment?
having small roots ensures water, making direct contact with the tissues of the plant, can diffuse directly into the leaves and stems
how does having airspaces in tissues benefit hydrophytes in living in an aquatic environment?
airspaces firstly help the plant with buoyancy, allowing it to easily float above the water, therefore maximising oxygen and sunlight uptake; these also create a pathway for oxygen to move from leaves to other parts of the plant which are submerged underwater
how are waterlilies adapted to their environment?
waterlilies firstly have airspaces in their tissues to allow these to float above the water, maximising sunlight and oxygen uptake; these also have wide, flat leaves which, likewise, maximise sunlight uptake