February 26, 2022
In this topic of IBDP Biology, we will learn about gas exchange in flowering plants.
Xerophytes
- Xerophytes are plants that are adapted to conditions where water loss is greater than its availability:
- Arctic
- Desert
- Sea shore
- Xerophytic adaptations – features designed to conserve water
- When it comes to IBDP Biology, there are 3 general forms of adaptation:
- Reduction in transpiration rate
- Storage of water – succulants
- Uptake more water
Reduction in transpiration rate
- Most xerophytes have few stomata.
- When it comes to IBDP Biology, they also have a thick cuticle – waxy barrier prevent water loss
- Marram grass:
- Has hinge cells to enable the leaves to curl into a tube.
- Water cannot diffuse through stomata as it is confined to inner surface
- Hairy epidermis – moist air trapped in hair layer, decreases diffusion path
- Sunken stomata – traps moist air above stomata, decreases diffusion path
- When it comes to IBDP Biology, cacti have reduced surface area of leaves – small and circular, reduces transpiration and help give rigidity when wilting.
- Photosynthesis is carried out by stem or petiole.
Storage of water
- Cacti and other desert plants have succulent leaves and stems.
- This stores water.
- This can be attractive to desert animals, so cacti have spines for leaves to deter them.
Uptake of water
- When it comes to IBDP Biology, cacti can have two sets of roots:
- Sideways to collect surface water from occasional showers.
- Deep penetrating roots to obtain water from a deep water table.
This is the end of this topic