NEED HELP WITH VPD!! MY LEAFE TEMPS ARE BASSACKWARDS!!

[Rickypohiogrower32]

I'm literally 10 to 12 in away from this Mars hydro ts-600m I'm getting leaf temps of 76° you know and if you look at my thermometer my hygrometer I'm sorrythe leaf temperature is cooler than the room temperature and I know that's bad ass backwards!! Right!!!

 

[Oa.ahhu]

Ambient temps need to be 8-10 degrees higher to achieve similar lst as if you we're using traditional hid light iirc.

 

[Aqua Man]

I'm literally 10 to 12 in away from this Mars hydro ts-600m I'm getting leaf temps of 76° you know and if you look at my thermometer my hygrometer I'm sorrythe leaf temperature is cooler than the room temperature and I know that's bad ass backwards!! Right!!!

No leafs temps are almost always lower. Unless you have a stupid amount of IR.

Also that doesn't look like an IR thermometer to measure leaf temp or am I wrong?

 

[Oa.ahhu]

No leafs temps are almost always lower. Unless you have a stupid amount of IR.

Also that doesn't look like an IR thermometer to measure leaf temp or am I wrong?

Depends on if he can adjust the emissivity of the thermometer

 

[Aqua Man]

If your placing a thermometer at the canopy and calling it leaf temps that's not correct. That's canopy temps. The evaporative cooling of the leaves almost always means they will be cooler than ambient or canopy temps.

 

[Oa.ahhu]

Leaf temps are taken from the stomata (bottom of leaf)

 

[Aqua Man]

Depends on if he can adjust the emissivity of the thermometer

Not exactly sure what that is but can you explain.

 

[Aqua Man]

Leaf temps are taken from the stomata (bottom of leaf)

Huh why? Leaf temps are leaf temps.

 

[Oa.ahhu]

Not exactly sure what that is but can you explain.

It's how light is reflected off of a given surface, cannabis is .97 to read lst if I remember it right.

 

[Oa.ahhu]

Huh why? Leaf temps are leaf temps.

Air/Water exchange is on the bottom of the leaf, when we take lst we are basically measuring the metabolism compared to certain standards , i read about it somewhere. Let me track down the link

 

[Aqua Man]

It's how light is reflected off of a given surface, cannabis is .97 to read lst if I remember it right.

Yeah is that not just a regular thermometer held at canopy level? Sorry you can't get accurate leaf temps like that. You cannot take into account the evaporative cooling that transipiration provides by refraction.

 

[Aqua Man]

Air/Water exchange is on the bottom of the leaf, when we take lst we are basically measuring the metabolism compared to certain standards , i read about it somewhere. Let me track down the link

Yeah that happens there but the temp of that thin and small of a surface you talking about 0.000001 temp difference between the underside and topside of the leaf... That has no bearing whatsoever on any possible impact of leaf temps from the top or bottom.

 

[Oa.ahhu]

Yeah is that not just a regular thermometer held at canopy level? Sorry you can't get accurate leaf temps like that. You cannot take into account the evaporative cooling that transipiration provides by refraction.

That is indeed an ir thermometer, but if he doesn't have the emissivity set correctly it won't be accurate.

 

[Aqua Man]

Man idk. This all seems unessasarily way over complicated. Looks like these may be out a bit like a degree or 2. And yes leaf temps will be cooler than air temps. A degree or 2 is not going to have big impact and certainly not the difference in temps between the underside and topside of a leaf

 

[Aqua Man]

Set it to surface temperature and that should be good.

 

[Rickypohiogrower32]

I have an infrared thermometer and I also have a hygrometer I really appreciate all the feedback so should I be taking my temps from the bottom or the top of the leaf?

 

[Rickypohiogrower32]

Set it to surface temperature and that should be good.

Thanks you.

 

[Rickypohiogrower32]

Thanks you.

Can you reiderate what kind of temps I should be shooting for maybe?? And thank you again for responding!!

 

[Oa.ahhu]

Yeah that happens there but the temp of that thin and small of a surface you talking about 0.000001 temp difference between the underside and topside of the leaf... That has no bearing whatsoever on any possible impact of leaf temps from the top or bottom.

Man idk. This all seems unessasarily way over complicated. Looks like these may be out a bit like a degree or 2. And yes leaf temps will be cooler than air temps. A degree or 2 is not going to have big impact and certainly not the difference in temps between the underside and topside of a leaf

I agree they will be very close

 

[Aqua Man]

I have an infrared thermometer and I also have a hygrometer I really appreciate all the feedback so should I be taking my temps from the bottom or the top of the leaf?

Tell ya what... Grab a leaf and do top and bottom. Post the difference. But I can tell you that thermometer is nowhere near sensitive enough to

Can you reiderate what kind of temps I should be shooting for maybe?? And thank you again for responding!!

Without CO2 I would say 77f is a good target for leaf temps.