nprofile1qy2hwumn8ghj7un9d3shjtnyd968gmewwp6kyqpqqs8ufsltqx5l6gzwaalvdugrhnta56842petwvajmw2rtrcmqjnsac77kd (nprofile…77kd) from what I understand it’s about the plants themselves not losing water due to evaporation loss.
Plants release a lot of humidity when they respire which is why they all do it at night when it is cooler and the sun isn’t shining on their leaves.
At midday in full sun, the surface leaf temp in 90F ambient temp can reach 140F - when plant leaf evaporation is its most intense. Cactus plants’ leaves evolved into tight coils (thorns) to avoid this kind of loss.