Light Bleaching 101

[Pinball Wizard]

Does everyone concur?...that this is light bleaching?..(I've never done/seen that before......)

Besides, moving them further from the light: any other suggestions?

 

[LJB]

Yes, increase the distance.

Just doing so slightly, 1/2 inch for example, would itself bring a major change to the number of photons falling on the plant.

 

[Bulldog11]

huh? I don't get it.

 

[LJB]

huh? I don't get it.

Response to me or the op?

 

[]A[Boss]

I don't believe that's light bleaching; my leaves, if light bleached, start looking like severe nitrogen deficiency.

How close have your lights been, and maybe make sure you have good airflow between light and plants.

 

[inefectualize]

that is heat stress not light bleaching.....put a fan on your bulb

 

[jaybutta]

that is heat stress not light bleaching.....put a fan on your bulb

Heat stress is exactly right...bleaching turns leaves straight white...best of luck...jay

 

[HansHanf]

hi pinball,

that is heat stress not light bleaching.....put a fan on your bulb

Heat stress is exactly right...bleaching turns leaves straight white...best of luck...jay

^^^second inefectualize and jaybutta on that,
last week my plants looked exactly the same as yours on the picture and it was heatstress and no ventilation-->exhaust gets broke and lighting hangs very close to the tops, way tooooo close....
how close are your bulbs?....

 

[LJB]

Heat stress is exactly right...bleaching turns leaves straight white...best of luck...jay

please post a picture if you have one, I would like to save it for reference.

 

[LJB]

is this what you all are talking about?

Strange that it's on the lower part of the plant in this example.

 

[LJB]

My first post was a little bit in haste. It is classic leaf scorch. But I'm still confused as to whether it's caused by by too much heat or too many photons.

I've experienced what can be seen in photo in post 10, but only on flower directly under the bulb, not lower down. I've responded by moving the lamps up slightly.

 

[vigilo]

the reason it would be on the low part of the plant is most likely due to water droplets magnifying the light to a powerful concentration. enough to bleach it

 

[LJB]

Can you add to that? Do you mean like if the gardener sprayed the leaves, or was messy while watering the roots, or do you mean droplets from transpiration?

 

[Weezard]

please post a picture if you have one, I would like to save it for reference.

Here's what light bleaching looks like with leds.


Aloha.
Weezard

 

[LJB]

Ok. In the op's picture, I see possible chlorosis in the lower leaves, yellowing tips on the some of the upper leaves and scorching in the middle that is similar to what can be seen on the two small leaves in the picture that Weezard posted.

And maybe (in OP's picture) the bud on top of the plant on the right has some color characteristics similar to the picture in post #10.

Does anyone think I'm nuts? Need eyes checked further? Should shut up? haha

 

[WeedChuck]

the reason it would be on the low part of the plant is most likely due to water droplets magnifying the light to a powerful concentration. enough to bleach it

will this myth ever die?????????

 

[Pinball Wizard]

Temperature has never gone over 80 degrees and never lower than 71. There has always been a fan blowing between the light and the canopy. Week#3...12/12

There are two thermometers: one at canopy...one on the floor.

400 watt CMH... ... ...I guess I'll have to wait and see what happens next?

 

[jyme]

looks like heat stress to me to.in the form of relitive heat.but you say you have good air exchange so tell me is your bottom leafs turning yellow. that cmh 400 hasnt got shit on the sun not even at 4 inches away. it could be a (P) deficency but looks more like RH

 

[jaybutta]

please post a picture if you have one, I would like to save it for reference.

I apologize I do not have one...but there are tons all over the internet...Merry Christmas to all...jay

 

[jyme]

looks like heat stress to me to.in the form of relitive heat.but you say you have good air exchange so tell me is your bottom leafs turning yellow. that cmh 400 hasnt got shit on the sun not even at 4 inches away. it could be a (P) deficency but looks more like RH

i meant Radiant temperature not relitive heat.Radiant temperature is the result of heat transfer bewteen objects at different temperatures without whats inbetween i.e. the air, being effected. In our case the plants are naturally at a lower temperature that the light and reflector so heat is transferred to the plants foliage from the light/refecltor through radiation. This causes the leaves to heat up. The plants can withstand much higher radiant temperatures (around 104-122degF) than they can air temperatures but if this is too high the plants can 'burn'.