How do cacti deal with keeping the stomata closed during the day to conserve water and use photosynthesis?

Question

I'm doing a science project but this a little confusing to me. Please help!

Answer 1

It's a special biochemical pathway known as CAM ("Crassalurian Acid Metabolism"). Photosynthesis itself involves using H2O and CO2 to make simple carbohydrates which then get built into more complex sugars like glucose, starch and cellulose. Plants using CAM open their stomata at night and use chemical energy to make simple sugars instead of solar energy. These sugars accumulate at night until the plant closes its stomata during the day and then uses sunlight to finish the sugar building process started the night before. This trick allows plants to conserve water by essentially holding their breath all day. With their stomata closed during the hottest part of the day, this minimizes water loss.