why does transpiration occur. I know it is a side effect of photosynthesis due to stomata opening but why does water evaporate into the air spaces from the mesophyll cell walls in the first place. is this the way plants rid excess water like how we do when we urinate?
It is to regulate the own water supply. To much or to few water and the plant fades.
Urination put it quite in a nutshell.
One of the main uses of water in a plant body is to help keep it turgid, prevent wilting, and is used for photosynthesis of course as well as help act as a body of water for transport of enzymes and nutrients of course. But what really surprised me is the fact that the plant doesn't use most of the water it absorbs via the roots, and only uses a very small percentage (not sure exactly.) A leaf will transpire many times more water than its own weight.
So basically, transpiration helps gets rid of this excess water it has due to the transpirational pull all day, but the MAIN reasons why transpiration is important is that it helps COOL the plant down.
Hope this helps.