Lighting What about light stress with too much Autocob goodness?

[Heliman]

[QUOTE="

And as for the statement previously that light stress doesn't exist....... check out those white tops on the same page the fella that said that!

All just IMO as always [/QUOTE]

I think you assume that white tops are ONLY a symptom of light stress ?? What is clear from this stimulating discussion is that we have not a definitive symptom for this phenomena ( if it indeed it exists).

I have an opinion, that I said I cant back up with real data, and I dont want to mislead. I have 5 plants growing just now, and 2 (Sativa dominant) have some whitening at the tips. As I am getting maximum PPFD of 295 it just CANT be light stress...but it sure could be heat or nutes or water or act of God...I dunno !!

Hopefully, with all the knowlege we have here we can get some dialogue going and maybe get to the bottom of the "light" issue

Cheers

 

[Hippy_BiotabsF70]

[QUOTE="

And as for the statement previously that light stress doesn't exist....... check out those white tops on the same page the fella that said that!

All just IMO as always

I think you assume that white tops are ONLY a symptom of light stress ?? What is clear from this stimulating discussion is that we have not a definitive symptom for this phenomena ( if it indeed it exists).

I have an opinion, that I said I cant back up with real data, and I dont want to mislead. I have 5 plants growing just now, and 2 (Sativa dominant) have some whitening at the tips. As I am getting maximum PPFD of 295 it just CANT be light stress...but it sure could be heat or nutes or water or act of God...I dunno !!

Hopefully, with all the knowlege we have here we can get some dialogue going and maybe get to the bottom of the "light" issue

Cheers [/QUOTE]

You're assuming that I'm assuming....

Nobody knows for sure mate, but that bleaching on the tops is a million times more likely to be light than anything else IMO. Opinion being the pertinent word here

 

[lunarman]

As far as the picture goes on page one the yellowing is at the bottom of the plant. That’s a mobile deficiency I believe. The plants drawing nutrients from the lowest less important leaves to feed the top ones. To me this means they aren’t getting what they need from the root zone.

You must mean my think different pictures. I'm using autopots with a res full of flower nutes. The plant is sitting in a tray full of nute water. So part of me thinks you must be wrong on the roots not getting what they need. But I will say that the medium in that particular pot might be to heavy and dense. I added biochar and EWC to coco and perlite. I have always had this gut feel that that mix doesn't work that well with the bottom feeding autopots. Its too dense. And when I measure my res level every day it is not going down as fast as I would have thought. So this plant might not be getting what it really needs for the roots, like you said. So this light stress thing might be a red herring at least for me in this case. But I agree that its an interesting discussion and will probably be debated for years. COBs or other LED lighting, auto flowering plants, nutes, and the whole dynamics and balancing act of all of it.

 

[BII]

What is clear from this stimulating discussion is that we have not a definitive symptom for this phenomena ( if it indeed it exists).

I think we can agree that some "phenomena" definitely exist. At some point AutoCOBs, all lights, can simply provide too much light. which becomes heat when absorbed. The major result of this would be heating of leaves, with them showing normal symptoms heat stress, such as canoeing or top ones just drying up. There can definitely also be light-induced bleaching of closest leaves/buds, with light-induced breakdown of chlorophyll. I don't think there is much room for disagreement on simply too much light leading to heating and plant pigment breakdown.

In practice, how much is too much with AutoCOBs in terms of causing observable stress? It's when you see the expected symptoms (which can also depend on many other factors, such as temperature, humidity, the plant, air flow....).

The real question we should be considering (or what I'd ilke to know) is:
Presuming AutoCOB lighting is not flat-out excessive, that plants are not showing the signs of the closer leaves over-heating, what is too much AutoCOB lighting? Then follow-on questions include: What basic lighting parameters are we talking about, such as PAR-related measurements vs. number of COBs/area vs. extent of overlapping vs. number of AutoCOBs per plant? And then the hardest question: Since at least to me "too much" is anything over the optimal amount: What is/are the optimal/best AutoCOBs configuration(s) in terms of plant potency, yield, judgement of quality, etc.?

 

[Hippy_BiotabsF70]

I think we can agree that some "phenomena" definitely exist. At some point AutoCOBs, all lights, can simply provide too much light. which becomes heat when absorbed. The major result of this would be heating of leaves, with them showing normal symptoms heat stress, such as canoeing or top ones just drying up. There can definitely also be light-induced bleaching of closest leaves/buds, with light-induced breakdown of chlorophyll. I don't think there is much room for disagreement on simply too much light leading to heating and plant pigment breakdown.

In practice, how much is too much with AutoCOBs in terms of causing observable stress? It's when you see the expected symptoms (which can also depend on many other factors, such as temperature, humidity, the plant, air flow....).

The real question we should be considering (or what I'd ilke to know) is:
Presuming AutoCOB lighting is not flat-out excessive, that plants are not showing the signs of the closer leaves over-heating, what is too much AutoCOB lighting? Then follow-on questions include: What basic lighting parameters are we talking about, such as PAR-related measurements vs. number of COBs/area vs. extent of overlapping vs. number of AutoCOBs per plant? And then the hardest question: Since at least to me "too much" is anything over the optimal amount: What is/are the optimal/best AutoCOBs configuration(s) in terms of plant potency, yield, judgement of quality, etc.?

Not sure how you did it mate, but you quoted me saying someone else's words!?

I agree with what you said above.