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gani when you read Dowd's and my own procedures they seem to work on opposite theories, but we can be sure of two things:
1. We are both being honest and factual about our procedures and results.
2. There is similar ground.
In general - strong light causes the plant to focus on photosynthesis and weaker or no light allows the plant to focus on root development. "Roots grow in the dark" adage. The T5 or floro light will not burn the leaves, but may take it's foucus away from root development.
Dowd's system may get around this with a longer dark period to offset the photosynthesis, both theories may work fine, or he may just be a better grower than I am. Light is needed or the cutting will die; too much light (without a sufficient dark period) may slow the rooting.
A good solution: Do both, see which works better for you.
I'm developing a pictorial in post 10 of this thread, if you want to try my single cutting cloners I'll work with you on that thread to get the results that you want.
https://www.rollitup.org/newbie-central/360125-new-growers-needed-grow-lab.html#post4545779
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bongsmlie