Heat does NOT cause a plant to wilt. Doesn't anyone google ANYTHING on this forum? A few weeks ago it hit 103 here in the shade... did all the plants in the city wilt?? Fuck no they didn't. You dont think it hits 80..90..100 in Jamaica and Afghanistan?
Plants wilt from one thing only, one. Wilting is caused by a reduction in turgor pressure. This is the pressure exerted on cell walls of the plant from water.
Sooo.. a plant wilts when water intake is less than water lost through transpiration.
So if your plant is wilting you have water movement problems. These typically fall into two categories.. problems us pros have and problems the newbs have.
1. Those that have been growing a long time usually see wilt because we forgot to water or were just too fucking tired to water. I know i know.. but YOU try to unconvince yourself that 640 3 gallon plants can make it another day without being watered.. it happens. Easily fixed
. Water them and they pop right back if they haven't reached the permanent wilting point.
2. And on to the new growers... killing with kindness. It seems dry, i should watet, i should water. Which ultimatly causes root rot. Your roots are slowly dying and at some point you dont have enough roots to support the tissues above the soil with enough water.... wilt.
This requires some repotting, soil sterlization, some TLC.
Of course other things can cause wilt... but what they are REALLY causing is a loss in the plants ability to uptake water.
These are things like root aphids, fungal disease blocking xylem channels...most often seen in seedlings, and a whole host of other pathogens that i cant provide a list of.
At any rate, water like the pros do. And here is how. Pot your plant and water it till runoff. Now pick it up. See how heavy it feels? Its pretty heavy because water is heavy. Now, dont water it until the soil is almost completely dry. How do you know this? The plant is JUST starting to wilt. Now pick up the plant... feel the difference? So from now on, dont water till you feel its really light again. When you do water, water everything till it starts to runoff.
You will soon learn how often they need to be watered throughout the lifecycle but you always know WHEN to water by simply picking up the plant.