VPD

Leaf temp is usually lower then air temperature. But what is going on when leaf temperature is 2-3 degrees higher then the air temperature?
I run tent temperatures 75-80. Right now RH is running 67-70. 4 weeks into Vege. Soil grow. Living soil.
Last several grows about 3-4 weeks into Vege. Leaf temp goes into positive.

Transpiration cools down the leaves , if your leaf temps are higher than ambient the plant is under alot of stress and is not transpiring.

Im having the same issue at the moment.
My VPD is set to 0.65 for early veg which keeps the RH between 64-69%

Ambient is around 23°-25° but just checked my leaf temp and it’s around 25.5° which means they ain’t transpiring?

They look healthy, but arnt showing signs of explosive growth by any means. Leaf temp should be 2° lower which is really annoying what it could be!

I just transplanted and topped. Maybe it is stress? See what happens in time.