420 Magazine Background

Light Bleaching


Member of the Month: May 2009, Oct 2010, Sept 2017
I just stumbled across a couple of articles that may help explain light-bleaching.

The first appeared in Plant Physiology, which is published by the American Society of Plant Biologists.
Plant Physiology said:
Established in 1926, Plant Physiology[SUP]®[/SUP] is an international journal devoted to physiology, biochemistry, cellular and molecular biology, genetics, biophysics, and environmental biology of plants. Plant Physiology[SUP]®[/SUP] is one of the world's oldest and most well-respected plant science journals.
Non-Photochemical Quenching. A Response to Excess Light Energy

The second appeared in the Journal of the American Chemical Society.
JACS said:
The Journal of the American Chemical Society (JACS), founded in 1879, is the flagship journal of the American Chemical Society and the world's preeminent journal in all of chemistry and interfacing areas of science. This periodical is devoted to the publication of fundamental research papers and publishes approximately 19,000 pages of Articles, Communications, and Perspectives a year. Published weekly, JACS provides research essential to the field of chemistry.

I just thought I'd share, lol.


Member of the Month: May 2009, Oct 2010, Sept 2017
It happens often with led lights when buds are too close to them.
I wonder if part of it - in regards to LEDs, specifically - is because people's grow rooms might not be reaching the same temperatures, and because of this, the plants are receiving more energy than they can process at their current temperature level?

Or if there is a component missing from LED panels (that are made up entirely of the individual mono-color LEDs) that, while not being directly involved in energy production, helps facilitate it? I really have no idea one way or the other about this. But my LED panel has a supplemental UV bulb in the middle of it, and I read a (single) comment in passing one day when looking for something else... The commenter's opinion was that "UV light helps the plants 'think' they are warmer than they actually are." I didn't pay any attention to it at the time (having been looking for other information), but now I find myself wondering if he meant that the plants would be able to process more light at a given temperature in the presence of UV? I know that high-altitude strains seem to do fine (at high altitudes), even though the temperatures can often be lower than the 77°F - 86°F range that I've seen being mentioned as "optimum" - and those plants, being at higher altitudes, would naturally receive more UV radiation than those being grown at sea level. Maybe if I see signs of bleaching, I should power up the UV bulb, lol? Or, alternatively, turn it on if I feel that the plants are dropping below their "comfort zone" level for the amount of light-energy that they're receiving? Hmm...

I wish I felt free to experiment at this time (hopefully next year). It might be interesting to grow multiple clones and make the only variable the amount of UV supplementation that they receive. I have read that (some portions of) UV may actually have a restorative effect on plants. I wish my brain wasn't in it's "dumber" end of the cycle right now. Oh well, that's what web browser bookmarks are for, lol.


New Member
Interesting thoughts. Just yesterday I noticed light bleaching in my room. The only variable would be temperature. Its been pretty cold here the last few days so the room is cooler than normal. Could this have contributed to the bleaching?


Member of the Month: May 2009, Oct 2010, Sept 2017
That's not something I have noticed before, but it's certainly possible in theory. Given ambient (IOW, non-supplemented) CO₂ levels, cannabis seems to be happiest with daylight temperatures of 77°F to 86°F (25°C to 30°C) or thereabouts, with it being able to use more light energy at 86°F than at 77°F. If daylight temperatures fall too much, you might discover that an amount of light which was adequate before... is now too much.


New Member
Great posts guys!

Just a thought of mine, possibly instead of turning to the UV light put a few single T5 bulbs vertical in your grow to give it more supplemental light. More cost effective and not a overload on the plant. Supply the optimum spectrum, dispersing the light so that it hits more space on the plant, leading to happy plant growth. Best of Luck, Happy Growing.


New Member
I think it must have something to do with light intensity, I only see this in flower tips that get close to my LED lights.
Top Bottom