Transpiration

Question 1

What is transpiration?

Answer 1

> loss of water vapour from the upper parts of the plants

> Water leaves through the leaf and the stomata

Question 2

Typical pathway of transpiration

Answer 2

> water enters the leaf through the xylem and moves by osmosis into the cells of the spongy mesophyll
water evaporates from the cells walls of the spongey mesophyll
water vapour moves through diffusion out of the leaf through open stomata, this requires a water vapour potential gradient

Question 3

Why is transpiration important?

Answer 3

> as water vapour is lost water must be replaced below drawing water up the stem which:

• transports mineral ions up the plant
• maintains cell turgidity
• supplies water for growth, cell elongation and photosynthesis
• water keeps plant cool

Question 4

Factors that effect trasnpiraton

Answer 4

> light intensity - stomata open to allow gaseous exchange
temp - increase rate of evaporation,increases rate of diffusion,decrease water vapour potential of air
humidity - decrease water loss as water wont diffuse out
wind - carries away water vapour keeping gradient high
water availability - stomata will close due to lack of water