Transpiration

Question 1

Water uptake and movement across the root

Answer 1

> mineral ions are actively transported into root hair cell to lower the WP
water moves into root cell via osmosis
water moves across root cortex by osmosis
mineral ions are actively transported into the medulla making the WP lower so water follows by osmosis

Question 2

Role of endodermis

Answer 2

> casparian strip blocks the apoplast pathway between the cortex and the medulla
- ensures water has to pass into the cytoplasm and membranes
membrane contains transporter proteins, pumping mineral ions from the cortex to the medulla
- makes WP of the medulla and xylem more negative so water moves into them
once water has entered the medulla it cannot pass back into the cortex

Question 3

Transpiration pull

Answer 3

> loss of water by evaporation must be replaced by water in the xylem
molecules are lost at the top of column so water is pulled up via cohesion

Question 4

Capillary action

Answer 4

> minerals actively transported into xylem lowering WP in xylem and water follows into xylem
water moves up xylem by mass flow assisted by cohesion
movement of water out of the top of the xylem creates low hydro-static pressure and tension
water moves across leaf via osmosis
water evaporates then diffuses out