The shape of the leaves tells the way they fall from the trees. The speed of the fall depends on two factors: the symmetry and the number of leaf lobes.
According to an innovative study, on May 7 at the Journal of the Royal Society Interface, rounded and symmetrical leaves, such as those of apple and ulmeiros, tend to fall faster and deposit near the base of the tree. Already the asymmetrical or lobby leaves – like those of the oaks – take longer to fall and are dragged by the air and end up resting further from the base.
The investigation of physical Matthew Biviano e Kaare Jensen From the Technical University of Denmark underwent the analysis of the leaves of 25 tree species, including oaks, ulmeiros, incers and apple trees and Arabidopsis, a plant with a genetic mutation that gives rise to asymmetrical leaves.
Replica replicas of three sheets of each species were created, which were then thrown into a tank full of water. The water resistance allowed to analyze the drop of the leaves.
Scientists noted that most leaves fell at a speed near the Theoretical maximum (represented by a circular disc, 1.37 cm per second). But Arabidopsis asymmetrical leaves fell about 15% more slowly.
The main conclusion of the study is that two factors determine the speed of fall: symmetry and the number of lobes. Artificially increasing the asymmetry of paper leaves, scientists pointed out falls between 15% and 30% slower. Symmetry was revealed the most determining factor: symmetrical leaves fall faster than lobby leaves, although the combination of both-asymmetry and lobes-produces the slower results.
Although falling aerodynamics is not the only factor in the evolution of the shape of the leaves, the new study suggests that there is an advantage in keeping the leaves near the tree after falling, as the nutrients that break free to decompose can be reused, Jensen explains.
