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Having A Light Source Too Close

Hey Dano, that's a great article, but all of yours are great, an informative, way over my head ,but I still love reading them.
You can tell easily ,when the lights too close, an they damn sure don't like it to close either, if your watching your plants.
 
Yea reading your plants is very important. But one aspect that goes overlooked is that the point between the compensation point and photoinhibition, can go unnoticed. Because the plant wont always show signs. Typically the plant can have a lower quantum yeild from chlorophyll avoidance or non-photochemical quenching. External symptoms such as bleaching doesnt happen until photoinhibition has initiated and damage has happend.

Still lots of work to do though.
 
Great article! I have often had thoughts about this. Also another thing you could maybe add or talk about to help people with the correct distance would be the shadows of darkness having the light to close would create. Causing under growth to get less and top to get to much..
i love when things get me thinking.
Merry Christmas
 
Yeah your right, damn near impossible to have everything right. Still what else you got but watching your plants as close as you can
 
I hear you BlueBudz, I like things that make me think, but I ain't like you an Dano, y'all got something to think with, I didn't get none of that. lol. MerryChristmas
PS- I'm still trying to figure out how to use a damn lux meter.
 
Thank you so much, for this information. Best article i've read in a very long time:
Whenever you do anything with cannabis- you must consider basic plant biology, which often is overlooked on many forums/posts.


I typically shoot for around 700umols at the canopy, but only use the companies PAR information chart.
The range you provided 500-1000 umols sheds light (pun intended) on why so many commercial growers have a PAR of around 510-525 umols at the soil or lowest leaf surface, keeping the entire plant in the zone.

The cure for so many grow problems- is to move the light away and watch the plant recover on it's own!
 
Yes i believe even just a basic understanding in plant biology can go a long way in horticulture.
Very right on commercial growers fixture heights. Quite often they hang their lights several feet high, as they understand about light physics and how light does not degrade and why uniformity is very important. They quite often only measure around 500umols at canopy like you say, but they will yeild the best out of any other setup.

I was a few hours in and was clearly getting very tired, the last half of the article needs work to improve readability. But i will leave that to later. There are also standing issues with embedded images on this forum.
 
Also I have searched Amazon for the book "Light measurement handbook." By Alex Ryer but cannot find it??
 
Vapor Pressure Deficit is the potential for water in leaves to move from a high humidity environment to a low humidity environment. Think of it like a towl drying on the cloths line. The towl is the leaves. Saturated in water. Gases and liquids want to move from high concentration to low concentration, which is what happens with the towl when it drys on the line. So the same thing happens with leaves and so moisture is vented out and creates water movement in the leaves and the entire plant because of the hydrogen bonds causing cohesion. So the movement of water is a completely passive process. Where as the movement of sap is partly active.
 
So "lights close as you can till you see a negative reaction and then back off slightly" is actually flawed thinking?

Psh it's tough to admit you are wrong sometimes but you have inspired me to swallow my pride.
I have to agree that if a plant is using resources to make a defensive reaction it will not be making headway towards botanical excellence.
So the tops of my Kush are starting to be veggie with thick dark twisted leaves coming out of the bud. But just where it's riding the line. I raised my lights about 3" today. Immediately afterwards they stink vs. yesterday they didn't, just one observation.

Thanks Danofdanger for sharing. Keep it up.
 
Exactly, thats what i was hoping would be interpreted. A plant may thrive with the "back off slightly after symptoms" method. But you could be holding back up to one third of usable energy that goes to waste. Of course you have to balance between good light placement and plant health. Because you can just as easily loose that much energy from having your light source too high.

Happy learning.
 
Some great info in this thread! Glad to know more about this now, I learned the hard way with keeping lots of extra distance for LED lights. Another benefit is the extra height will help give a little "safety room" during the stretch!

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