The Q&A Archives: Photoperiods of Lettuce

Question: I an a seventh grader at South Range Middle School in Greenford, Ohio. I am doing a science project on growing leaf lettuce under flourescent lights. I have two sets of plants growing under different light cycles. The first set has a light cycle of 16 hours on and 8 hours off. The second set has a cycle of 2 hours on and 1 hour off in a continuous cycle. Do you know if the different light cycles will have any effect on the growth of the lettuce plants?<br><br>

Answer: That's a clever idea for an experiment. A few thoughts come to mind. First, do you have a way of keeping the plants in the dark during their "off" cycle--especially the ones on the 2-hr on, 1-hr off cycle? Are they in the classroom, where they will receive "ambient" classroom light--that is, the lights that you normally have on in the classroom? Or are the plants in a dark place like a closet so they will be in total darkness during the "off" times?<br><br>Also, often the mostdramatic effects of various light cycles can be seen in the way plants produce flowers. You may see some difference in growth of your lettuce plants, but if you have time you might also try some easy flowering plants like marigolds, to see if the light cycles affect the length of time it takes them to form buds, the total number of flowers, and the size of the flowers, for example. <br><br>I hope this is helpful; good luck!

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