The temperature inside a healthy, photosynthesizing tree leaf is affected less by outside environmental temperature than originally believed, according to new research from biologists at the University of Pennsylvania.
Surveying 39 tree species ranging in location from subtropical to boreal climates, researchers found a nearly constant temperature in tree leaves. These findings provide new understanding of how tree branches and leaves maintain a homeostatic temperature considered ideal for photosynthesis and suggests that plant physiology and ecology are important factors to consider as biologists tap trees to investigate climate change.
Tree photosynthesis, according to the study, most likely occurs when leaf temperatures are about 21°C, with latitude or average growing-season temperature playing little, if any, role. This homeostasis of leaf temperature means that in colder climates leaf temperatures are elevated and in warmer climates tree leaves cool to reach optimal conditions for photosynthesis. Therefore, methods that assume leaf temperature is fixed to ambient air require new consideration.
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