Earth Equity News

Trees Regulate Leaf Temperature for Photosynthesis. By Heidi Ledford, Nature.com, June 11, 2008. "Whether growing in the heat of Puerto Rico or in the icy chill of northern Canada, tree leaves are able to buffer against the outside temperature, new research has found. A survey of 39 North American tree species over an area spanning 50° of latitude has shown that plants protect one of their most important functions -- photosynthesis -- by maintaining average leaf temperatures at around 70 degrees F, regardless of the weather. The findings, published this week in Nature, could have implications for how scientists use tree rings to model past climates, and how they predict future responses to climate change... Plants use several mechanisms to adjust their temperature. Some cool off by changing the angle of their leaves relative to the sun, or using fine hairs as a kind of sunscreen. They can also 'sweat,' sacrificing water for the cooling effects of evaporation. Meanwhile, trees in cold climates may clump their leaves... so that each is less affected by the weather... Trees that have adjusted to cold temperatures in this way may have a particularly hard time coping with the warming brought on by climate change."