According to Simcha Lev-Yadun, from the University of Haifa-Oranim (Israel), and Jamo Holopainen, from the University of Kuopio (Finland), the causes must be sought 35 million years ago . When the green color of chlorophyll decreases in the leaves, the yellow pigments that already exist in the plant become dominant in certain species and become visible. In red-leaved plants something different happens: as the green chlorophyll disappears, a new red pigment is synthesized, called anthocyanin. The work points out that in the American continent a long evolutionary battle took place millions of years ago between the trees and the insects that stay in them and that absorb the amino acids from the leaves in autumn, then laying their eggs, to the detriment of the plants. As the researchers explained in the Journal New Phytologist , the trees chose to invest part of their energy in changing the leaves from yellow to red to scare off insects .
In Europe, however, with so many mountainous areas , when the ice ages and glaciations followed one another, many species of trees did not manage to survive the cold, and many insects either, so that the plants that resisted the frosts did not. It is necessary to take the step of substituting the yellow color of its leaves for the reddish one .
