Plant & zo
The science of plants and more
Touch
An obstacle influences plant growth. How a plant registers touch is not completely clear. Long did researchers think plants observe touch with help of their trichomes, the hairs on a leaf. But not all plants have hairy leaves. Now a group of American, German, and Danish researchers show that the pavement cells at the outside of a leaf observe touch.
After observing touch, plant cells sent a signal to their neighbouring cells, who in turn sent the signal onwards to their neighbours. This signal consists of a temporally increase in calcium concentration. In this way generate plants a wave of temporally increased calcium concentrations. Something researchers can measure using fluorescent sensors.
The signal tells the plant if it is growing against an obstacle
Using a microscope, the researchers studied this calcium signal. There they noticed that straight away the fluorescent sensor lights up when a single cell on the outside of a leaf was touched, after which sometimes the sensor was also turned on in neighbouring cells. In addition, 20 to 50 seconds after touch, the researchers observed a signal that slowly moved from cell to cell. When they let go of a leaf the researchers noticed in some leaves a fast signal traveling from cell to cell.
What is happening between observation of a touch and the sending of a signal is not jet clear. But the researchers think that there is a correlation between the intern pressure the cell experiences, and the speed of the signal. The pressing of the cell while touching it, increases the internal pressure, which is followed by a slow signal. While by letting go of a cell, the internal pressure is suddenly lower, which result in a fast signal. In this was a plant knows if it is growing against something, or away from it.
Literature
Alexander H. Howell, Carsten Völkner, Patrick McGreevy, Kaare H. Jensen, Rainer Waadt, Simon Gilroy, Hans-Henning Kunz, Winfried S. Peters & Michael Knoblauch (2023) Pavement cells distinguish touch from letting go. Nature Plants https://doi.org/10.1038/s41477-023-01418-9
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