Plant exchange and excretion

Packed with chloroplasts Structure of the Leaf Large surface area Lots of chlorophyll Transparent Thin structure Packed with chloroplasts Network of veins Lots of air spaces Holes

Gas exchange in the leaf The structure of the leaf allows plants to carry out gas exchange. carbon dioxide in (daytime) : photosynthesis Oxygen in: respiration. Oxygen + water vapour : OUT

Wide spaces between ground cells – diffusion

The Stomata The function of the stomata is gas exchange. Each stoma is a gap that is found in between two Guard cells. The Guard cells control the opening and closing of the stoma.

The stoma and the guard cells When water enters the guard cells they swell and have a curved shape. The gap ( the stoma) opens up between the two cells. When water leaves the guard cells they shrink and the gap between the two cells (the stoma) closes.

The stoma (open) and the guard cells

Carbon dioxide controls the stoma The opening and closing of the stoma depends on the levels of carbon dioxide in the plant. When CO2 levels become low inside the plant water enters the guard cells and the stoma opens up.

Carbon dioxide controls the stoma When CO2 levels are high in the plant water leaves the guard cells and they close. This happens at night

Lenticels Lenticels are small openings in the bark of a tree where gas exchange happens.

What about trees and woody plants ? Lenticels often look like tiny raised blisters on a branch or twig.

Winter twig – showing lenticels

Plant excretion Def Excretion is getting rid of waste of the metabolism from the body Plants do not need to excrete a lot of waste: They make their own food so they have reduced food waste to get rid of They use most of the products of their metabolism in their bodies – i.e. oxygen is produced as a product of photosynthesis but is used for respiration. Stomata and lenticels are the only organs of excretion. They excrete oxygen and water vapour.