Join Date: Feb 2007
Location: "The Old Line State"
To answer your question, yes and no. You can grow most plants with lights on 24-7--we do that with some plants at my school (with mostly C4 grasses like corn, sudangrass, phrag, etc) . Also, take for example plants growing in far northern regions of the world, such as Alaska. In their summer, they get 24 (or close to 24) hours of daylight per day, and plants grow like crazy (Alaska is famous for produce huge pumpkins). But with other plants it will not work. Take for example, CAM plants, which require darkness to fix carbon.
A day-night cycle is beneficial and necessary to regulate some plant physiological functions, such as flowering. And I'm sure there are also some other functions in plants which are controlled by a dark and light period. So to answer your question, yes, many plants can be grown in 24 hours of light, while some can't, and others (most) will benefit from a day/night cycle. So in general, it is best to grow plants with some sort of dark period. Also, with aquarium plants, leaving the light on for 24 hours is just asking for an algae problem.
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