If I want to close my stomata during the day, but I need CO2 during the day, how can I solve this problem? And what desert plants, or many desert plants, have evolved to do, essentially does photosynthesis, but instead of fixing the carbon in outer cells and then pushing it in to inner cells and then performing the Calvin cycle, instead of outer and inner cells, they do it at the nighttime and in the daytime. So in CAM plants-- and these are called CAM plants because,