a) What process is responsible for the movement of carbon dioxide into a leaf?
b) In what conditions might the same process cause oxygen to enter a leaf?
(a) Diffusion is responsible for the movement of carbon dioxide into a leaf.
(b) Oxygen will disperse into a leaf when the concentration of oxygen inside the leaf is lower than its concentration in the air outside. This might happen in low light intensities when the rate of respiration exceeds the rate of photosynthesis.