3.3.4.2 Mass Transport in Plants

Question 1

Explain how the active transport of mineral ions into the xylem vessels in the roots results in water entering these vessels and then being moved to the xylem tissue

(hint root pressure)

Answer 1

The water potential in the xylem is reduced by the entry of ions. So a water potential gradient is established between the xylem and surrounding cells.

The plasma membranes of the surrounding cells are partially permeable
So water enters the xylem via osmosis.
So the volume of water in the xylem increases

And so the pressure in the xylem increases as water cannot move back down due to the concentration gradient