Photosynthesis at Night

Contrary to popular belief, photosynthesis does happen at night in some plants. These plants are called CAM plants, and their stomata, the openings that allow water evaporation, only open at night to conserve water. Many of these plant species belong to the cactus family and thrive in hot, dry environments.

Saguaro cactus in the deserts of Arizona.

Their advantage is that they are more efficient in their water usage by not allowing it to evaporate during the day. They only allow evaporation at night because there is no sunlight, lower temperature, and lower wind speeds. CAM plants are often seen as having a major advantage over other plants in many areas because of their extra efficiency. But with the growing threat of light pollution, the photosynthetic processes of CAM plants are being negatively affected.

This dead barrel cactus could exemplify the effect of light pollution on CAM plants.

They open their stomata when there is naturally less light, but in places where the level of brightness has reached near daytime levels due to artificial lights, this adaptation hurts them. Instead of conserving water, the artificial lights will cause a higher transpiration rate than they are used to, reducing their health and interrupting their photosynthetic pattern. Reducing the health and by default the population of a influential plant like cactus can have a great effect on the surrounding ecosystems.

There has not been much research done on the effects of light pollution on photosynthesis, so not much is known about how great of an effect it can actually have. But based on knowledge of CAM plants and the process of photosynthesis, we can assume that an unnatural abundance of light can have a negative effect.

For more information on the workings of CAM plants and other types of photosynthesis:
Photosynthesis-An Overview
CAM Plants YouTube Video
CAM Plant-Dictionary Definition