An injury to a single root can alert other underground parts of a plant almost immediately.
Researchers observed this mechanism in Arabidopsis thaliana, a small plant widely used in laboratories. When a root is cut or damaged, the pressure inside its cells drops sharply. This change then spreads through the water-filled tissues that run throughout the plant.
Roots.
Pixabay illustration
The phenomenon is fast: the pressure wave advances at approximately 75 mm/s. At this speed, it travels 7.5 cm in one second. The researchers indicate that it moves about 10,000 times faster than some calcium waves already observed in plants.
To understand what happens next, we need to look at the cells in the roots that remain intact. Some proteins in their membrane respond to mechanical stress. One of them, called MCA1, detects the change caused by the wave and transforms it into electrical signals and variations in calcium within the cell.
In other words, the plant very quickly converts a physical disturbance into a biological message. The signal then reaches other cellular actors and promotes the production of stress-related hormones. Nearby roots can thus alter their state before a new injury occurs.
This communication is not, however, identical to that observed in leaves. In roots, the intensity of the signal decreases with distance from the injury. The researchers link this limited range to the underground environment, where pests such as larvae and nematodes move slowly through the soil.
These results could help improve our understanding of how crops respond to organisms that attack their roots. Underground damage often remains difficult to detect before its effects on the plant become apparent.