Why are a plant's stomata generally open during the day and closed at night?

The stomata is the part of the plant that allows them to breathe. These are usually found underside of leaves since it is cooler in this part and so that, water won't evaporate quickly too. Guard cells usually keep stomata open during the day and closed at night because during the night there is no sunlight for photosynthesis. Hope this answer helps.

If you eat to much it could kill you.