Tree leaves control their own temperature

U.S. scientists say they've found the temperature of a photosynthesizing tree leaf is affected less by outside environmental temperature than believed.

University of Pennsylvania scientists studied 39 tree species from subtropical to boreal and discovered a nearly constant temperature in tree leaves. The researchers said their finding provides new understanding of how tree branches and leaves maintain a homeostatic temperature considered ideal for photosynthesis.

Tree photosynthesis, the study says, most likely occurs when leaf temperatures are about 21 degrees Celsius, with latitude or average growing-season temperature playing little, if any, role.

It is not surprising to think that a polar bear in northern Canada and a black bear in Florida have the same internal body temperature, said Professor Brent Helliker. "They are endothermic mammals like us and they generate their own heat.

However, to think that a black spruce in Canada and a Caribbean pine in Puerto Rico have the same average leaf temperature is quite astonishing, particularly since trees are most definitely not endothermic.

The research appeared in the online edition of the journal Nature.

(UPI)

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