Structure of a Leaf

Question 1

how is the leaf specialised for gas exchange?

Answer 1

• the leaf is thin, so the diffusion is short
• it also has a large surface area, increasing the number of stomata, so that carbon dioxide can diffuse quicker
• stomata allow gases to diffuse into/out of the air spaces of the leaf - this provides a short diffusion distance to the mesophyll cells
• gases include moving into/out of the leaf include water vapour (lost in transpiration), oxygen (absorbed at night for respiration) and carbon dioxide (absorbed for photosynthesis)
• the guard cells form the stomata and can change shape, altering the size of the stomata
• the stomata close to reduce water loss (and gas exchange) - this happens when the plant has lost too much water - the guard cells become flaccid, so the cell walls are not held apart and the stomata shrink?