She served as a frame pulling the stem perpendicular to the ground.
French biologists from the National Center for Scientific Research conducted an experiment with vascular plants. They found out that the driving force of trees, which makes them rise up, is the bark. The work was published in The New Phytologist.
Previously, scientists assumed that the "engine" that counteracts gravity is located inside the tree trunk. The latest experiment changed these ideas. For the botanical experiment, nine tropical tree species were selected: Cecropia palmata, Laetia procera, Pachira aquatica, Simarouba amara, Virola michelii, Cordia alliodora, Tarrietia utilis, Gossypium hirsutum, Theobroma cacao. They raised eight to 12 specimens of each species. The growth period ranged from three to ten months. The trees were then transplanted into pots at a 45-degree angle, tying the trunk to a post. The samples were kept in this position for three months.
The New Phytologist.
After the support was removed, the trees stretched upward, perpendicular to the ground, forming a curve towards the bottom of the trunk. Then the scientists removed the bark. Representatives of five out of nine species have lost the resulting bend. To understand the cause of this phenomenon, the researchers looked at the internal structure of the bark and stems.
Schematic changes in the structure of the cortex / The New Phytologist.
Biologists found that the fibers of the cortex formed lattice structures. They suggested that the growth system in these trees is similar to that of Carica papaya. In this case, in their opinion, the driving force is radial growth, which increases the perimeter of the cortex and pulls it out. Uneven stretching leads to different deformation of the lattices on the inner and outer parts of the bark, which causes curvatures and helps the plants overcome gravity.
Alexey Evglevsky
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