Why do mimosa shrink when it touches leaves?

It turns out that there is an enlarged organ called "leaf pillow" at the base of the petiole of mimosa, and there are many parenchyma cells in the leaf pillow, which is very sensitive to external stimuli. Once it touches the leaves, the stimulation will be immediately transmitted to the occipital bone. At this time, the cytosol in parenchyma cells began to flow into the intercellular space, which reduced the expansion ability of cells, reduced the intercellular pressure in the lower occipital region, and the leaves closed and the petiole drooped. 1-2 minutes later, the cell fluid gradually flows back to the leaf pillow, so the leaves return to their original appearance.

The above phenomenon of Mimosa leaves is a physiological phenomenon, and it is also the result of Mimosa adapting to the external environment for a long time in the process of system development. Because the mimosa originated in the tropical region, where there are many storms, when the storm blows the leaflets, it immediately closes the leaves to protect them from the storm, thus gradually forming this physiological phenomenon.