Higher conc. of water vapour (100% saturated) In plastics bag – 90% humidity No plastics bag – 70% humidity The drier the air, the steeper the concentration gradient, the faster the rate of transpiration.
night time day time Guard cells turgid Stoma Opens Guard cells flaccid Stoma Closes Stoma
Think about it!! Why placing the vegetables in a plastic bag helps to reduce transpiration? It helps to keep the humidity of the air surrounding the vegetables high.
Wilting Rate of transpiration > rate of absorption of water What happens to the leaves when they wilt?
Wilting • How does wilting benefits the plants? • When leaves fold up, the surface area exposed to the sunlight is reduced. • Stomata closes • Transpiration decreases
Wilting • Disadvantages of wilting • Stomata closes • Carbon dioxide cannot diffuse into the leaves • Carbon dioxide becomes the limiting factor for photosynthesis
Normal condition Desert plant Guard cells Guard cells Lower epidermis Lower epidermis
Guard cells Habitat of marram grass Leaves of marram grass
Hawaii Silversword Flowers Leaves
Guard cells Guard cells Lower epidermis Leaves covered with silver hairs
Desert plant • Adaptations: • Sunken stomata • How it helps: • The enclosed region around the stomata helps to retain water vapour • increases humidity Guard cells Lower epidermis
Adaptations:- Leaves covered with silvery white hair How it helps: -Reflect light lowers temperature of the leaves