Plants use light to fuel growth. If they receive less light they will grow less. Changing the light/dark light cycle to 10/14 from 12/12 reduces the amount of light the plants receive by 1/6, or 16%. Cutting the light cycle while flowering results in less total growth, because the plant produces less material used for tissue building.
Another effect of cutting the light cycle is to hasten the ripening of the plant. By reducing the light cycle during the growth part of flowering, the growth time is reduced. However this is not a productive trade-off. Not only is the total time under light reduced, so is the percentage of time with light. The yield of the lower light-cycle bud will be more than proportionately lower than normal.
However, during the last 10 to 15 days of flowering the bud has little growth. Instead it transforms as the stigmas dry, the ovary behind them swells and the glands fill with THC. Reducing the light period during this time will hasten ripening without significantly reducing yield, by giving the plant a clear signal that the time has come.
There are occasions when it may be more important to speed up ripening than to maximize production. Under these circumstances, a 10-hour light/14-hour dark cycle would indeed be better.
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