How do the plant muscles fold the mimosa leaf quickly?

We call them motor plants. Or lizard plants. Tiny swellings of specialized cells in the mimosa plant can fold feathery leaflets in seconds, then relax – and do it again.

A new look on these noses Mimosa chaste The plant has revealed the details of how the leaf manages its usual speed of folding, says biomechanist David Sleboda of the University of California, Irvine. “I think these particular organs are really cool because their movement is reversed,” he said. “[W]A chicken is seen by humans as a reversible movement of a plant, and it feels much more like an animal’s movement.

Scientists have already developed the basic chemistry that makes the little mimosa motor, or cushion, work, he and his colleagues write in a paper due Dec. 6. Current Biology. When a deer’s hoof or something else creepy hits a leaf, potassium and other ions transfer from one side of the cushion to the other. A stream of water follows the ion. Cells that lose water deflate and sag while those on the other side bloat. The multiple deformations of the cushions make the halves of the feather fold into each other, like an invisible hand gently closing a book.

A side view of a folded mimosa leaf shows muscle-like cushion structures (orange) where chemistry creates temporary microsurges of water that bloat some cells while others sag, thus exposing parts of the leaf into position.DA Sleboda et al/Current Biology 2023A side view of a folded mimosa leaf shows muscle-like cushion structures (orange) where chemistry creates temporary microsurges of water that bloat some cells while others sag, thus exposing parts of the leaf into position.DA Sleboda et al/Current Biology 2023

Instead of studying chemistry, Sleboda and colleagues looked at the details of the microscopic structures in cushion cells that help create such beneficial distortions, he reported February 7 at the annual meeting of the Society for Integrative and Integrative Biology in Austin, Texas. One feature that makes plant muscle cells bloat more effectively is microscopic fibrils. They act like scabs, which hold back cells that swell from all sides. But the corset directs much of the swelling along the axis, which will fold the leaf in half.

The cushion also has cells that are needed for rapid swelling that appear as folds of tissue expanded to facilitate the flow of water, and particularly in highly perforated zones called pit fields. See wells that if the water could easily trickle through the leaf in an emergency. The cell arrangement itself looks special for expansion and contraction. A cross-section of the pillow reveals a pattern “like the leaves of a concertina,” Sleboda said.

Latos M. pudicaor sensitive plant, is one of the best known leaf benders. However, clusters of other plants in the same family, vegetables, also move their leaves, botanist Thainara Policarpo Mendes of Universidade Estadual Paulista in Botucatu, Brazil. Some relatives fast like that M. pudicabut many more slowly. What he also thinks, though, ends completely. People have proposed different benefits: discouraging animals from feeding on a plant that suddenly looks more visible, or even helping the plant lose less heat during the coldest nights.

Sleboda can also relate to the proposed hypotheses, but he remains a skeptic of all. “There’s not a ton of research,” he says. But that’s it. “My favorite thing about sensitive plants’ leaf closure,” he says, “is that we don’t know why they do it.”