Updated: Dec 8, 2020
When cannabis plants, like other green plants, are in the light—be it sunlight or artificial light(street light)—they are photo synthesizing. This is how they convert light into energy and release oxygen. They are also respiring. That’s right, contrary to the misinformation circulating elsewhere, plants, like all other aerobic organisms, are respiring all the time.
We stop when we die, and we die if we stop. Cannabis plants are just producing a surplus of oxygen during the daytime. During the dark cycle, cannabis plants are not photo synthesizing, and continue to respire at a constant rate; they do not just begin to respire when the lights go out.
We had some plants that were getting too much street light at night and after about a month we noticed that it was not growing as full on that side. It was clearly visible so we decided to put a dark colored tarp in front of the area where the street light was hitting at night. Our plan worked and after the tarp was left there for a few weeks we noticed the plant was getting bigger and more full on that bad side.
So we came to the conclusion that the plant was not getting enough darkness on that side. The plant went from looking weak and dark green to a more stronger and brighter green color.
The street light was one of those very bright lit LED lights. They just replaced all the street lights on our block with these. Next May we are going to make sure we pick a better spot for our outdoor weed garden.