05-03-2010, 02:44 PM
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What happens if you drop the lighting too much? How do you know if you need to increase it?
Plants require adequate light to photosynthesize: adequate means sufficient intensity and duration. The nutrients have to balance the light. Plants will photosynthesize (grow) according to the law of minimum, which is that the requirement that is in least supply is the point which determines when plant growth stops. When light exceeds what the plants can utilize, because the nutrients are not sufficient for them to continue to grow, algae uses the light and takes advantage.
If the light is too little in intensity, the plants cannot manage to photosynthesize (grow). Similarly if there is insufficient duration. I don't know the specific point at which growth would cease; but the siesta method of having the lights on for 5-6 hours, off for 2-3, then on for 5-6 works because plants can use the 5-6 hours to grow but algae interestingly cannot do so as successfully. Most authors I've read suggest a minimum of 8 hours is the limit.
We learn much from regular observation. An occasional yellowing leaf is not a problem if the plant is sending out new growth and the new leaves are good. The new growth, its appearance and rate, is what I monitor.