Usually, we learn in school that there is only one way that plants photosynthesize. If you're a cactus, a pineapple, and even an orchid, that's just not true - you are most likely growing in a harsh, dry, unforgiving environment (well, if you're an orchid, you may be in a picture window, but you have aerial roots, most likely). Therefore, you need to conserve water as much as you can, and that includes during photosynthesis. Learn more about how CAM plants adapt in order to save water and to thrive in arid environments.
And, okay, you can stop pretending you're a cactus or a pineapple or an orchid now.
Photo: Peggy Greb, USDA-ARS.