Xerophytes & Transpiration Factors

1. Xerophytes & Transpiration Factors

2. xerophytes • A plant adapted to live in dry conditions • They have a range of adaptations to reduce the loss of water vapour by transpiration.

3. xerophytes • Leaves • Small to reduce the surface area • Thick to reduce surface area: volumes ratio

4. xerophytes • Sunken Stomata

5. xerophytes • Stomata • Set deep inside the leaf so that they are at the base of a depression full of water vapour • Some plants open their stomata at night to store and absorb CO2

6. xerophyte • Thick waxy cuticles • reduce water loss through the epidermis

7. Xerophytes • Rolling up of leaves • Lower surface faces inside and traps humid air next to the stomata • Varies with conditions

8. Xerophytes • Leaf hairs • Trap damp air • Reduces air movement • Cut down transpiration

9. Factors Affecting Transpiration

10. Potometer • Measures the water absorption • Estimate the rate of transpiration • Air/water tight • Water transpired • Water entering to xylem

11. Factors affecting rate of transpiration Light intensity: • Affects the opening and closing of the stomata • ROT • Indirect effect

12. Factors affecting rate of transpiration Humidity: • Humid atmosphere • Contains a lot of H2O molecules • Reduction of the water potential gradient between the air spaces and atmosphere • ROT decreases • Low humidity increases ROT

13. Factors affecting rate of transpiration Temperature: • Temperature • kinetic energy • Rate of diffusion through the stomata pores • Air is able to hold more water molecules at higher temperatures • ROT

14. Factors affecting rate of transpiration Wind speed: • Still air makes the H2O molecules to accumulate around the stomata pores (leaves) • Reduces the H2O potential gradient and slows the ROT • Wind disperse H2O molecules • gradient in H2O potential ROT