I've read that efficiency of photosynthesis is only like 5%, and it operates on visible light spectrum, not infrared (which is heat radiation). Which means light should either be absorbed and increase plant temperature, or reflected, and heat what's around the plant. But when you get near or touch plants under sunlight, they are at ambient temperature. In contrast, if you touch a metal plate, ceramic tile, rubber, plastic, asphalt, concrete, sand etc, that's exposed to strong sunlight, they are very hot, either because they reflect heat onto you (sand), or because they absorb heat and their temperature is high (asphalt). But with plants, it seems like neither happens, and it stays cool. How does that work?
Take a look at the
Temperature paragraph from this reference:
Plants can avoid overheating by minimising the amount of sunlight absorbed and by enhancing the cooling effects of wind and transpiration.
They seem to have several ways to counter the heat as we do with transpiration, wind etc.
This article is more complicated but as really useful informations on the effects of wind on the plant's temperature:
You mix several things.
- logic: if the plant converts some of the radiation into energy rather than heat + reflection, then it's normal that it heats less than some other object with same amount of reflection.
- physics: the feeling of cold/hot object is related to his thermal conductivity more than its temperature. That's why walking on wood/wool doesn't feel the same than on steel.
- physics+bio: plants are mostly made of water, and thus evaporate, which cool them down. Steel doesn't.