Why plants send distress signals to their roots after being injured

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

http://www.dfac.cc/showtopic-17-283335-0-0-1.htm

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 study on plant physiology and nervous systems, scientists claim that they found in their research that when plants are attacked by pathogenic bacteria, the 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 crisis.

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 already discovered that plants actually have multiple ways of calling for help. Bais used a pathogen called Pseudomonas syringae to infect the leaves of Arabidopsis thaliana, and the Arabidopsis thaliana soon began to show symptoms. However, after a beneficial bacterium called Bacillus subtilis was introduced to its roots, the diseased Arabidopsis thaliana 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 antimicrobial protective film around the plant roots.

Using molecular biology methods, scientists examined 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 show that the plant's self-defense response is 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.