Why Trees Are Not (Much) Higher Than 100 Meters Are
Biophysicists explain growth limit with blade sizes: For taller trees were neither large nor small leaves suitable
leaves on trees have very different shapes and sizes, which can range from a few millimeters to over a meter. Little known and not yet explained is a curious fact: the higher tree species can be, the more similar their green extremities: All giant trees – like the giant sequoia, or eucalyptus – ten to 20 centimeters large leaves.
Is that a coincidence or necessity? As botanists have pressed this issue so far, Kaare Jensen (Harvard University) and Maciej Zwieniecki went biophysically (University of California at Davis) and ask the question in the “Physical Review Letters” on a new theory. Which is not trivial, and assumes that sheets produce by photosynthesis an energetic liquid flowing through the vascular system of the tree to the roots. The greater the sheet is, the higher the speed of the liquid, which pushes the root of resistance. And this resistance is greater, the higher the tree.
Above a certain size of the tree, the resistance is so great that even the giant blades do not help. Very small leaves are also bad. Jensen and Zwieniecki have cast these considerations for large and small leaves in equations, the curves intersect at 100 meters. The researchers compared their data with 1,925 species of trees and their leaves – and found her theory confirmed.