Question

Why are most plants unable to run the calvin cycle at night?

Answer 1

The Calvin cycle cannot operate during the night, as light is needed to convert carbohydrate molecules into chemical energy. However, some plants that have evolved (due to arid conditions) to utilize CAM photosynthesis (Crassulacean acid metabolism)--which the plant shuts it's stomata during the day, in order to reduce evapotranspiration, but open at night, to collect carbon dioxide. Thereby, making the majority of plants unable to compensate like these select few plants--that have evolved to do so.