Question

Explain why the rate of diffusion of carbon dioxide into stomata on a leaf is higher on a warm day

Answer 1

The stomata control gas exchange in the leaf. Each stoma can be open or closed, depending on how turgid its guard cells are.

In the light, the guard cells absorb water by osmosis, become turgid and the stoma opens.

In the dark, the guard cells lose water, become flaccid and the stoma closes.

Diffusion of carbon dioxide, oxygen and water vapour into (or out of) the leaf is greatest when the stomata are open.

Answer 2

An increase in temperature increases the rate of evaporation and decreases the relative humidity of the environment. The more stomata on the leaf, the more water evaporates the leaf.

In addition to lowering carbon dioxide levels during photosynthesis, light can have a direct effect on guard cells, causing them to swell.