It’s been a long time since I posted and even longer since I was active.
I’ve been studying the relationships of the effects on root zone temperature to dry weight and have come to a few conclusions.
For those who are interested (please forgive me if I’m covering an old topic) I’ve been looking specifically at the sweet spot of root temperature to increase overall weight.
So most of you hydro growers will know that low water temperature will cause slow growth, affect plants resilience to disease and pests and lower yeilds.
The same can be said about root temperatures/nutrient solutions that are too high.
On average 12c or lower and 25c or higher will cause significant problems in general.
But a 13 degree difference is a massive parameter to work with. Luckily there’s more specific plant research out there that zeroes in that difference to being ideal temperatures of your roots/medium is between 17-23c with as little fluctuation as possible in a 24 hour period. Think of how rapidly your grow room cools down when the lights turn off… This can cause significant stress to your plant and lower yeilds.
If we go up the scale something interesting happens, at 23-27c your roots will actually go into overdrive and you’ll see pretty explosive growth. Sadly this doesn’t equate to higher yields. In fact you’ll have more airy buds, more stalk and very lanky plants. This is obviously an issue when your plants are going into their stretch period when flipping to flower.
To combat this we might want to slowly reduce the light cycle to even out the rapid temperature drop, or we could also think about having some small tube heaters on a thermostat that come on when your lights go out (or we can do both in different combinations.) This is of course assuming you don’t have water heaters/chillers in your res that your setting.
As a coco grower I don’t have this luxury but even when I’ve grown using traditional hydro methods I’ve only bothered with heaters and chillers when running much bigger grows. The best results (this surprised me) I’ve had haven’t been with a soil/water probe connected to tube heaters and set to a particular temperature but using an external thermostat built into the heaters
So (and most importantly!) The sweet spot for optimum nutrient uptake temperature range I’ve found is between 28/32c (at the top of the plants) with lights on and a drop to 18/19c (controlled by tube heaters around 2" off the ground) when the lights go off.
There’s a ton more science involved here and I’m more than happy to go into depth or answer anything I’ve missed.
Again, please accept my apologies if this teaching you lovely people to suck eggs and I hope this makes sense and is useful 
