Can plants photosynthesize all-day?

Question

If a plant was given sunlight even during the night, with appropriate constant intensity during day and night, will the plant be able to maintain health and normally photosynthesize throughout the day? Does it depend on specific plant species? If so, are there particular categories of plants that may have problems with all-day photosynthesis?

Answer 1

They can still photosynthesize. Photosynthesis is sometimes divided into the light and dark cycles, but it would be more accurate to call these light-dependent and light-independent reactions. The light-independent cycle, where NADPH is oxidized to NADP+ and CO2 is converted to glucose, can still happen if light is available. It just doesn't depend on photons, like the light-dependent reactions do.

Still, most plants do not do well with all-day light. This isn't because of issues with photosynthesis, but because of a few other factors:

1) Too much light can burn the plant, especially if there is high light intensity or high heat (tomatoes are especially sensitive to this)

2) A lot of flowering plants (including poinsettia) need darkness to flower

3) Plants, like many animals, have something similar to a "circadian rhythm", where periods of light and dark help them regulate things like starch metabolism