R2101 4.4 Describe the relationship between leaf structure and physiology

Question 1

How do leaves affect photosynthesis?

Answer 1

1. Shape of the leaf blade - generally thin to allow light to penetrate to all the chloroplasts in the pallisade layer
2. The arrangement of the leaves on the stem to allow light to reach the maximum number

Question 2

Where are stomata in dicots and why?

Answer 2

In most dicots are on the underside of the leaf, the shadier side to reduce transpiration.

Question 3

How is the entry and exit of gases and water vapour controlled in the leaf?

Answer 3

The stomata are opened and closed by water pressure in the guards cells.

Question 4

How does the palisade mesophyll layer assist with photosynthesis? (2)

Answer 4

1. The cells are close to the surface of the leaf
2. The chloroplasts can move round in the cells to maxmise their exposure to sunlight

Question 5

How does the spongy mesophyll layer assist with photosynthesis? (2)

Answer 5

There are loose packed cells with lots of inter-cellular spaces to allow the free movement of gases and water. The stomata open into these spaces

Question 6

Role of the cuticle?

Answer 6

A protective waxy coating which helps to stop the leave drying out, and keeps some pathogens out of the leaf tissue