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In-depth discussion ---- Plants send distress signals to their roots after being injured

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Scientists in the United States recently said that in a study they found that when plants suffer external damage, they can send chemical signals to their roots to seek help.

In this research on plant physiology and nervous systems, scientists claim that they found in their study that when plants are attacked by pathogenic bacteria, their leaves send distress signals to the roots. After the roots receive the distress signals, they immediately respond by secreting an acidic substance carrying beneficial bacteria to resolve the situation.

Harsh Bais, a professor of plant and soil science at the University of Delaware in the United States, explained that people generally believe plants are most vulnerable to attack by harmful fungi or bacteria yet show no response. But we have found that plants actually have multiple ways of calling for help. Bais used a pathogenic bacterium called Pseudomonas syringae to infect the leaves of Arabidopsis thaliana, and the Arabidopsis quickly began to show symptoms. However, after a beneficial bacterium called Bacillus subtilis was introduced to its roots, the diseased Arabidopsis was able to recover quickly. Farmers can also apply fertilizer containing Bacillus subtilis to the soil to enhance plant immunity, and Bacillus subtilis will form an antibacterial protective film around the plant roots.

Using molecular biology methods, scientists detected this distress signal transmitted from the leaves to the roots. Roots growing in soil containing Bacillus subtilis respond to the signal and secrete a carbon-rich chemical substance -- malic acid. Bais explained that all plants can synthesize malic acid, but only under special circumstances or for a specific purpose. In the experiment, the plants actively secreted malic acid to attract Bacillus subtilis. Enlarged images of the roots and leaves showed that the plant's self-defense response was provided precisely by this beneficial bacterium. Scientists have not yet figured out exactly what this distress signal transmitted from the leaves to the roots is, and this question still requires further experiments and research.