Sensitive to touch
Environmental signals help to optimize growth. In this way tells the ratio red versus far-red light if there is an obstructing neighbouring plant. But a touch is also informative. Now Dutch researchers discovered how a plant perceives this kind of long duration touch.
When the ratio red versus far-red light tells that there is an encroaching neighbouring plant, then a plant lifts its in the shadow laying leaves. By touch the reaction is the same. But so discovered the researchers, the underlaying mechanism is different. Plants that could no longer respond to a changing light ratio, still responded to touch.
Calcium the messenger
From earlier research it is known that upon touch that with calcium a signal can be sent. With help of a fluorescent sensor that perceives calcium, the researchers analysed if this was also happening in this situation.
When the researchers touched the tip of the leaf for a long time, then the sensor lighted up after about 4 minutes. Only after about 7 minutes the researchers observed a wave of calcium flowing from the top of the leave to its base. When the researchers blocked this calcium signal, then the plant did not lift its leaf upon touch.
Essential leaf hairs
Trichomes, those hairs you see on leaves, are one of the first cells of a leaf to that touch another leaf. Zooming in on those trichomes, the researchers noticed that after touch that the calcium sensor at the base of those trichomes lights up.
To confirm that those trichomes are indeed needed for the reaction to touch, the researchers looked at trichome less plants. The noticed that without trichomes that the touch induced calcium signal is less strong. Moreover, the plants did not lift its touched leaf.
And this is a disadvantage for the plants. In dense vegetation trichome less plants were growing less well the researchers noticed. Showing at the same time, that a timely reaction to a neighbouring plant prevents growth loss.
Literature
Pantazopoulou, C.K., Buti, S., Nguyen, C.T. et al. Mechanodetection of neighbor plants elicits adaptive leaf movements through calcium dynamics. Nat Commun14, 5827 (2023). https://doi.org/10.1038/s41467-023-41530-0
Plant en Zo 