Inside a Tree Leaf, It’s Always a Balmy 70 Degrees

Who knew that a white spruce in northern Canada, a red maple in Pennsylvania, and a mahogany tree in Puerto Rico have so much in common? Their environments are certainly very different, with icy winds buffeting the spruce tree's needles and hot, humid air bathing the mahogany tree's leaves. But despite these external variations, a new study shows that inside each tree leaf (or needle) it's always just the right temperature for the delicate and vital process of photosynthesis, and the leaves are responsible for keeping that thermostat steady. The findings, published in Nature [subscription required], show that trees all across North America favor the temperature of 70 degrees Fahrenheit for the photosynthesis process, which uses sunlight to convert carbon dioxide into oxygen and sugars. To keep in that comfort zone, they've come up with some clever adaptations. Trees release water, and during hot times, that botanical sweat cools them ...