Leaf Temp, Air Temp, or Both?

[American Hillbilly]

Do you chase leaf temp, air temp or a combination of the two? I read so many different numbers when it comes to temps my head spins.

My top of canopy leaf temps at a measured 700 PAR under a HLG led are 72 degrees with a room temp of 80. The lower leaves are cooler. Even when I bump par up in flower, I get 4-6 degrees below room temp.

I feel 72 degrees is too cold. I can up my room temp easy enough but at what point should I be concerned with my room being too hot? At least one source claims 82 is the perfect leaf temp for photosynthesis. That would put me in the upper 80s for room temp.

I guess I’m trying to understand if there are negatives to the room temp being too high if leaf temps are good? Or should I just find a nice balance of room v leaf temp and call it good?

 

[Death The Cultivator]

Do you chase leaf temp, air temp or a combination of the two? I read so many different numbers when it comes to temps my head spins.

My top of canopy leaf temps at a measured 700 PAR under a HLG led are 72 degrees with a room temp of 80. The lower leaves are cooler. Even when I bump par up in flower, I get 4-6 degrees below room temp.

I feel 72 degrees is too cold. I can up my room temp easy enough but at what point should I be concerned with my room being too hot? At least one source claims 82 is the perfect leaf temp for photosynthesis. That would put me in the upper 80s for room temp.

I guess I’m trying to understand if there are negatives to the room temp being too high if leaf temps are good? Or should I just find a nice balance of room v leaf temp and call it good?

I've flowered at 82-86f in hot summers with a leaf temp around 79f and humidity in the 60s. Higher temperatures increase photosynthesis, works well with c02, but can cause drought stress and nutrient issues when VPD is not met.

dimluxlighting.com/knowledge/vapor-pressure-deficit-vpd-calculator/

Ambient temperature is offset by the temperature of the leaf surface in conjunction with the humidity levels gives you the kpa. Pick the stage your plants are in and be consistent with it. I don't like growing above 77f if I can help it, terps are less volatile at lower temperatures but I don't hate growing clones/moms/flowering at 80f and 65% humidity either.