Gee64
Well-Known Member
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.Thank you Con! I think the same about your pics in your tranquil oasis by the lake.
Thank you SniperX! My jars are emptying as we speak so I will be very grateful for this harvest. Your outside autos are looking like jewels they are so green.
Thank you GDB! I hope one day I can measure my success by floppage
Thank you Keith! Exciting times. Yours are about to start the flowering magic too
Thank you Otter, they are getting fatter, especially the MAC#1 auto. I got some pics with the flash on, that always shows the buds nicely. The Red Mimosa XL auto is a couple of weeks behind the MAC#1 and the Blueberry is about a week behind that. I'm hoping they will pack on the weight too. The Red Mimosa certainly is frosting up.
Thanks G, the smell is pretty awesome too.
Moisture Update:
Thanks to this very useful gift I am able to see exactly how moist the plants like their pots to be. Here are some pics of optimal soil moisture and present status. It's great to be able to see this and know what to aim for.
Previously my plants in the 20 L (5 gal) pots would take about 2 L of water each time and require watering more frequently. Now these plants only take 1 L at a time. I put this down to the light control. I wonder if that can be.
Perhaps when I was running the lights too hot and for too long that may have sped up the transpiration. Now that I am keeping DLI within the suggested range, at 45, with much lower ppfd, I feel my plants have a better chance at remaining healthy and bulking up. @Gee64 do you think this is a thing?
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.
OKaaay, good to know! So there is possibly a case to be made to turn the dial down to 75 % and move the lights closer. I remember 
) light.
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