I think it's the the colon ??
Answer:
CO2 enters the stomata during the day when they are open for photosynthesis. In exchange, O2 exits the stomata. While the stomata are open, there is a risk of water loss resulting in wilting and maybe death. The stomata help to conserve water at night while they are closed. Also, their waxy covering “cuticle” helps minimize water loss. On a very hot day, the stomata May close to preserve water but it comes with a cost, because if they close, photosynthesis slows down.
Explanation: