Transpiration has a great influence on maintaining water cycle as level of water is getting low day by day, leaves release water in form of water vapour which is in pure form and also doesn't give to low water cycle.
Transpiration is nothing but evaporation of water from lower portions of leaf.even though plant consumes more water only 2 percent of it is actually utilised rest of them are absorbed by sun.the main reason for this is it is also a part of evaporation if there is no transpiration there is no rainfall so to maintain it transpiration must continue.