Re: Do plants require SOME darkness in order to grow?

Some plants, such as tomatoes, are harmed when they are exposed to more than 
about 18 hours of light per day. I believe the tomato leaves under continuous 
light developed lesions of some sort. However, a lot of plants seem to have no 
problem with continuous light. 

Light and dark reactions occur at the same time in the light. The term "dark 
reactions" is misleading because those reactions do not actually occur in the 
dark. The dark reactions do not need light themselves but do need the products 
of the light reactions. A lot of botanists prefer the term Calvin Cycle or 
Calvin-Benson Cycle instead of dark reactions.

It doesn't matter if your hypothesis is correct or not. What is important is 
how you interpret your results.


Reference

Salisbury, F.S. and Ross, C. 1985. Plant Physiology. Belmont, CA: Wadsworth.