Transport in Plants

Question 1

How does water having a high specific heat capacity help buffer changes in temperature?

Answer 1

Can gain/lose a lot of energy without changing temperature

Question 2

Give 2 properties of water & explain their importance in cytoplasm

Answer 2

Polar molecule - acts as solvent
Solvent - reactions occur faster in solution

Question 3

Describe the cohesion tension theory of water transport in xylem

Answer 3

Water lost from leaf because of transpiration, which lowers water potential of mesophyll. Water is pulled up xylem. Water molecules stick together by hydrogen bonds forming a water column. Adhesion of water to walls of xylem

Question 4

Explain how xylem tissue is adapted for its function

Answer 4

Long tubes with no end walls so continuous water columns.
No cytoplasm to obstruct flow.
Lignin keeps water in cells
Pits in walls allow lateral movement

Question 5

Evidence to support cohesion-tension

Answer 5

If a trunk or stem is damaged and a xylem cell is broken water does not leak out. Once air enters the tree can no longer draw up water because the continuous column of water has been broken.

Question 6

Evidence to support cohesion-tension - diameter

Answer 6

The trunks of trees reduce in diameter during daytime. Stomata open in light which means more water loss. Water evaporates more when warm. Water molecules stick together by hydrogen bonds forming a water column. Adhesion of water to walls of xylem. Xylem pulled in by tension