Plant Repiration – Need to Turn the Lights Off?

Q: I have an office cohort who says I should turn the lights off so the plants can respire. I’ve left them on and the plants seem to grow quite well. Should I indeed turn the lights off when I leave?

A: Plants respire twenty-four hours a day, using up sugars made by photosynthesis. You don’t need to turn the lights off to allow respiration. The problem comes when a plant grows in constantly warm temperatures. It doesn’t cool down and thus uses up just as much sugar as it makes. It’s best to drop the office temperature at night (I’m sure this happens where you work) to allow some of the food made during the day to be stored and used for future growth.