It is definitely a thing. Light is radiation and it has the ability to raise the temperature of a leaf. Transpiration is dictated by the difference in leaf temp to air temp. There are certainly other factors such as air movement, but a warm leaf will dry quicker just as water on a warm sidewalk will dry quicker than water on a cold sidewalk. It's physics at play. VPD to be exact. Too much light will cause both sunburn, which lowers future photosynthesis, and dehydration.

I actually just tried this to see and what I found was a lower volume of light closer to the plant gave a more even PPFD right out to the edges of the lights footprint.

I'm not sure on the penetration part as I have no way of measuring that but my logic is leaning me to believe that a flat even canopy is better served by a closer light set to proper PPFD and an untopped plant with colas at varying heights is better served by a higher hung light turned brighter, but thats a guess as again, I have no way of knowing which actually penetrates thru leaves better.

I circumvent the entire dilemma by delarfing anything that doesn't get full light thus removing the penetration factor from the equation. But again, I have no real idea. I just set PPFD to 950 max at the brightest cola (autos seem to be able to safely handle more) and then not really worry about it after that.

Light intensity definitely affects transpiration tho. Moving wet air out and dry air in also has a huge bearing on transpiration too, but temp offset between leaf and air is what creates the rate of transpiration.

Moving air ensures that rate doesn't get compromised.

They are gorgeous Carmen😍❤️👊. Don't go overboard on dryness tho, a 5 is perfect for flower with photoperiods. For autos I'm not sure.

Also scrub that probe with a scratchy plastic scrubby and good dish soap to remove factory grease from it or you may get improper readings, and don't leave it in the soil when you aren't using it. It will corrode and then you will need to use steel wool to revive it.
Excellent post G, thanks, very educational.
 
Sunday Bud Porn!
Howdy and happy Sunday. I wish you all only happy memories and no regrets. Love till the stars go out!









They look beautiful Carmen. I skipped a few pages to catch up, but now I need to go back to see the transformation!
 
Highya Carmen,

Beautiful colors!! Mimosa and Blue Dream are gorgeous with all the different colors, and the pistils turning! Does that mean they're nearly ready for harvest? Mac1 could be called Big Mac, but she looks so much better than the hamburger!! Looks like she's lagging the other two. They all look gorgeous!! Happy Sunday, and Happy Smokin'
 
They look beautiful Carmen. I skipped a few pages to catch up, but now I need to go back to see the transformation!
Hey 024! Thank you. They've come along pretty well with a bit of a K deficiency. I've managed to contain it in the RMXL auto but the MAC #1 auto is a bit of a concern. Some of the sugar leaves are looking a bit damaged. I need to catch that.
They're gonna stunnnn when they full bloom!! The colors are to die for. Love that pallet💚
Thank you Jiggi! I hope the 🎨 is a sign of the cool weather and not the deficiency. It may be a bit of both.
ahhh, what way a to spend my Sunday,looking at purdy sparkle buds an listing to the Rasta man vibrations. scuz me whilst i light up
:green_heart: Light it brother, light it!
Wonderful job Carmen! Looks like you have everything dialed in, the grow is beautiful!
Thank you Gid!
Highya Carmen,

Beautiful colors!! Mimosa and Blue Dream are gorgeous with all the different colors, and the pistils turning! Does that mean they're nearly ready for harvest?
Thank you Bode. I'm terrible at guessing how long they have left. I'd say a few weeks to go still. The pistils have just started to turn.
Mac1 could be called Big Mac, but she looks so much better than the hamburger!! Looks like she's lagging the other two. They all look gorgeous!! Happy Sunday, and Happy Smokin'
Thank you! Yes the MAC #1 buds are nice and chunky indeed. Bigger and fatter than a lighter. The others are more lighter-sized and so I hope they fatten up too.
 
I rember paying a buck fifty to go to Bruins an Celtics games. I saw Black Sabbath there and honestly thought the building was gunna collapse. The good ole days. or some really vivid dreams / flashbacks
I grew up in Lynn so that was the place to go! Yeah, I can't believe it didn't shake down after some of the concerts and events! That balcony used to move!
Sunday Bud Porn!
Howdy and happy Sunday. I wish you all only happy memories and no regrets. Love till the stars go out!









These are so lovely, and we get a color show too!
 
Sunday Bud Porn!
Howdy and happy Sunday. I wish you all only happy memories and no regrets. Love till the stars go out!









Looking great Carmen getting some nice colors 👌
 
I grew up in Lynn so that was the place to go! Yeah, I can't believe it didn't shake down after some of the concerts and events! That balcony used to move!

These are so lovely, and we get a color show too!
Thanks Otter :)
Looking great Carmen getting some nice colors 👌
Thank you Con :)

However, I am concerned about minimizing damage on the MAC #1 auto. I have been treating this plant for K deficiency and I am not seeing improvement. If anything, I am seeing this leaf burn creeping into the sugar leaves on the main and some other colas. Please have a look at this and tell me what you think folks.

DSC_9034.jpg
DSC_9036.jpg
DSC_9038.jpg
DSC_9040.jpg


Should I treat with calmag maybe?
 
These are a couple of shots of the Blueberry auto buds. See how small.
20240806_161428.jpg
20240806_161424.jpg

Then here are some shots of the Red Mimosa XL auto. Also small.
20240806_162002.jpg

20240806_161947.jpg
 
Highya Carmen,

I'm not the right person to answer, but I'll muse a little trying to understand some more. Some spots look like they could use calmag. The edge burns look like they are nutrient burn And the first ones look like nothing is wrong, just color creeping into the edges. Only you know how much of what you've been feeding, so maybe this'll trigger something in your mind. Hope that helps. Always a pleasure! Happy Smokin'
 
Thanks Otter :)

Thank you Con :)

However, I am concerned about minimizing damage on the MAC #1 auto. I have been treating this plant for K deficiency and I am not seeing improvement. If anything, I am seeing this leaf burn creeping into the sugar leaves on the main and some other colas. Please have a look at this and tell me what you think folks.

DSC_9034.jpg
DSC_9036.jpg
DSC_9038.jpg
DSC_9040.jpg


Should I treat with calmag maybe?
WooHoo!

I think you are close enough to harvest to not chase after fixes? I would just continue with what you have been doing?

Great Recovery! ❤️
 
Highya Carmen,

I'm not the right person to answer, but I'll muse a little trying to understand some more. Some spots look like they could use calmag. The edge burns look like they are nutrient burn And the first ones look like nothing is wrong, just color creeping into the edges. Only you know how much of what you've been feeding, so maybe this'll trigger something in your mind. Hope that helps. Always a pleasure! Happy Smokin'
Thank you Bode. I've been chatting with Gee because he knows my soil build and the history quite well. I'm leaning towards a calcium deficiency at this point.
WooHoo!

I think you are close enough to harvest to not chase after fixes? I would just continue with what you have been doing?

Great Recovery! ❤️
Thank you MedScientist. I think there are a couple of weeks to go still, so I'm going to take a chance and dose the plant with tomorrow's watering. The burnt sugar leaves trouble me.
I just wanted to mention that too much K locks out calcium.
Thank you Shed. I still see signs of what I think looks like K deficiency but it is possible that calcium is locked out for another reason too. I've run through the list with Gee and the temperature of my soil has fluctuated to as low as 15 C and as high as 21 C. Other than that, everything is in safe limits. I think I'll do a dose of calmag tomorrow 🤞
 
the temperature of my soil has fluctuated to as low as 15 C and as high as 21 C
All sorts of things don't happen down at 15ºC as described in this post:

You're hovering down near the lowest temps that cannabis is fond of, ruderalis or no. :)

I know there's nothing to be done about the temps, but it's possible that throwing nutrient boosters may not be helpful if the soil is below the range that the roots can take them up.
 
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