Possible heat stress? Only when nearer to end of light cycle. Pics included.

goatlicker

goatlicker

Well-Known Member
Hey guys,. so i lowered my lights from 18inch to 14inch the other day and noticed they looked like heat stress the next morning before the lights turned off.
I took the light up to 16inch and tried again last night but this morning they're quite bad again so have taken them back to 18inch.
The temps never really changed at the plant height, and its only affecting 2 plants, third seems to be sweet.

First Photo shows just as lights turn on, and the rest are from this morning.

Main question is.. is this definitely heat stress or light stress?
And will they recover with the light back at 18 inches now? and should i just leave it at 18inh, Its a 400w MH.
 

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shawnery

shawnery

Well-Known Member
86 degrees is pretty hot.
38 humidity is pretty low.

Together these will definitely cause issues with heat strees and vpd(vapor pressure deficit).
 
goatlicker

goatlicker

Well-Known Member
shawnery said:
86 degrees is pretty hot.
38 humidity is pretty low.

Together these will definitely cause issues with heat strees and vpd(vapor pressure deficit).
Click to expand...
The actual temp of the room is around 77degrees, thats directly under the light so theres a lot of radiant heat.
The 24.5c is temp taken underneath a leaf at the canopy height.
I haven't had any issues up till now and its been that temp and humidity for the whole time.
 
hotrodharley

hotrodharley

Well-Known Member
goatlicker said:
Hey guys,. so i lowered my lights from 18inch to 14inch the other day and noticed they looked like heat stress the next morning before the lights turned off.
I took the light up to 16inch and tried again last night but this morning they're quite bad again so have taken them back to 18inch.
The temps never really changed at the plant height, and its only affecting 2 plants, third seems to be sweet.

First Photo shows just as lights turn on, and the rest are from this morning.

Main question is.. is this definitely heat stress or light stress?
And will they recover with the light back at 18 inches now? and should i just leave it at 18inh, Its a 400w MH.
Click to expand...
Heat stress. Raise the light more. Get air moving.
 
goatlicker

goatlicker

Well-Known Member
hotrodharley said:
Heat stress. Raise the light more. Get air moving.
Click to expand...
Yeah i figured, it happened straight after i moved the lights, I have them back up at what they were at (18Inch)
Will the recover and go back to normal or just stay like that?
So that means i can't lower my lights lower than 18 inch?
I tried 14 and 16 and they both made them canoe.
I have a 2 small fans blowing air around, between the light and plants.

Updated pic of them now the lights just turned on.
 

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hotrodharley

hotrodharley

Well-Known Member
goatlicker said:
Yeah i figured, it happened straight after i moved the lights, I have them back up at what they were at (18Inch)
Will the recover and go back to normal or just stay like that?
So that means i can't lower my lights lower than 18 inch?
I tried 14 and 16 and they both made them canoe.
I have a 2 small fans blowing air around, between the light and plants.

Updated pic of them now the lights just turned on.
Click to expand...
I can't get mine any closer except with an air cooled reflector. My 600 watt HPS can be about a foot away in the air cooled. My 400 watt no less than 18" or heat stress. It's not cooled.
 
goatlicker

goatlicker

Well-Known Member
hotrodharley said:
I can't get mine any closer except with an air cooled reflector. My 600 watt HPS can be about a foot away in the air cooled. My 400 watt no less than 18" or heat stress. It's not cooled.
Click to expand...
Ah thanks, that makes me feel a bit better.
Ill keep it at 18, it seems to be fine at that.
Hopefully that fixes it, Will those leaves go back to normal?
 
hotrodharley

hotrodharley

Well-Known Member
goatlicker said:
Ah thanks, that makes me feel a bit better.
Ill keep it at 18, it seems to be fine at that.
Hopefully that fixes it, Will those leaves go back to normal?
Click to expand...
They should. They just do that to dissipate heat. Give a bit of cal mag. Stress increases calcium use by the plant.
 
goatlicker

goatlicker

Well-Known Member
hotrodharley said:
They should. They just do that to dissipate heat. Give a bit of cal mag. Stress increases calcium use by the plant.
Click to expand...
Sweet, they seem to be better at the height it is at now but ill check tmrw morning and hopefully not have it all canoed.
They all just got a feed of cal/mag with their last feed 3 days ago.
 
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