GCSE Biology Question

Hi, could someone please help me with this? From what I understand, gases enter and leave the leaf through stomata. During the day, guard cells open the stoma so CO2 can enter and O2 can leave the photosynthesising leaf. At night the guard cells close the stoma to prevent water loss. How then can oxygen enter the leaf at night for respiration??

Thanks in advance.

I think you're getting confused with the purpose of stomata. Stomata open so gasses can be exchanged (yes, you're right so CO2 and O2 can leave the leaf) but they open for photosynthesis (does not occur at night, as there is no sunlight). They close to control water loss in a leaf, so the leaf doesn't dry up through evaporation.

Now onto respiration... Guard cells do not open and close for respiration, they control water loss and adapt to get the maximum amount of photosynthesis. For plants using respiration, they manufacture glucose in their leaves and use glucose for respiration. They can turn this energy for growth and for new cells. Remember, respiration is the process of releasing energy from glucose, which goes on in every cell... NOT "Breathing In or Out" (which is what I think you think it means)

Hope it helped and ask if you still don't understand

Thanks for your reply! I understand that respiration is for release of energy, but do plants not respire aerobically meaning that they need oxygen as well as glucose to respire? If so, where does the oxygen come from? Thanks again!