Gas Exchange in Plants

Question 1

Material Exchange in plants

Answer 1

During daylight, photosynthesis is taking place in plants. They are taking in CO2 and releasing O2 into the atmosphere. Plants are able to use diffusion to move carbon dioxide and oxygen into/out of leaves.

Plants will also take up liquid water via roots, which may also contain minerals like nitrates and phosphates.

Plants will also lose H2O in the form of water vapour through their leaves.

Question 2

Photosynthesis vs Aerobic Respiration

Answer 2

Photosynthesis takes place in chloroplasts (found in mesophyll cells in leaves):
Photosynthesis converts carbon dioxide and water into oxygen and glucose. Glucose is used as food by the plant and oxygen is a by-product.

Respiration mostly takes place in organelles called the mitochondria. Chemical energy is released for the plant to use (repair, growth etc.)Cellular respiration converts oxygen and glucose into water and carbon dioxide. Water and carbon dioxide and energy is produced.

Question 3

Respiration in plants

Answer 3

During daylight plants hcarry out photosynthesis and aerobic respiration. Photosynthesis will occur at a faster rate, due to the abundance of sunlight available
This means there is a nett release of oxygen taking place.

At low levels of sunlight, there are similar rates of photosynthesis and respiration taking place.
This means there is no nett exchange of gases taking place.

At night, there is no photosynthesis taking place, but the plant is still undertaking respiration.
This means there is a nett release of carbon dioxide taking place.

Question 4

Leaf Structure

Answer 4

• Structure allows for gas exchange w/ external environment.
• Lower epidermis contains stomata to permit the entry/exit of gases. Stomata can be open and closed.
• Spongy mesophyll. This section of the leaf has air spaces that allow CO2 and O2 to move around easier.

Question 5

Stomata

Answer 5

Stomata have two guard cells that surround a pore. The guard cells can change their shape based on their water content, opening and closing the pore. This allows the plant to have some control over gas exchange.

typically open during the day to favor CO2 diffusion when light is available for photosynthesis, and close at night to limit transpiration and save water