As far as I can tell, if you have the basic information - temperature, air pressure, and partial pressure of water vapor - then RH, dewpoint, and VPD are different ways of looking at the same thing. There are formulas and tables that let you get to any of them or convert between them. I grew up with RH. The weather people now, at least in the US, like dewpoint, for technical reasons, and the crop science people like VPD, also for technical reasons.
I also use Bluetooth enabled sensors (SensorPush), and it lets me display any or all of those three values. I tend to look at RH first since I'm most familiar with it, but I've got the VPD display turned on and am trying to get used to looking at it for the greenhouse sensor.
I agree strongly with Peter that leaf temperature is in many, maybe even most, cases, more important in knowing whether the plant is too hot than is air temperature, especially with C3 plants. High levels of photorespiration can become detrimental very quickly. (What I can practically do about that in my growing situation, other than more shade, is unfortunately a whole other question.)
The only real use I make of any of those numbers is deciding whether to spray water on the GH floor to increase RH/reduce VPD for the cuttings and seedlings, since they're so sensitive to water stress.
Thanks for the link to "Plant Empowerment", Peter. Looks like some good information there.
I also use Bluetooth enabled sensors (SensorPush), and it lets me display any or all of those three values. I tend to look at RH first since I'm most familiar with it, but I've got the VPD display turned on and am trying to get used to looking at it for the greenhouse sensor.
I agree strongly with Peter that leaf temperature is in many, maybe even most, cases, more important in knowing whether the plant is too hot than is air temperature, especially with C3 plants. High levels of photorespiration can become detrimental very quickly. (What I can practically do about that in my growing situation, other than more shade, is unfortunately a whole other question.)
The only real use I make of any of those numbers is deciding whether to spray water on the GH floor to increase RH/reduce VPD for the cuttings and seedlings, since they're so sensitive to water stress.
Thanks for the link to "Plant Empowerment", Peter. Looks like some good information there.