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In the modern world we live in today, perhaps the most rapidly innovative industry we have is the field of communication. Just think about how far we have come in the last twenty years: from the days of simple analog land-line calls to the advanced cellular networks and ongoing digitization of land-lines that we are witnessing today.

Two years ago, a really good friend of mine was involved in a pretty critical automobile accident in which he sustained severe injuries and was left unconscious after the initial impact. If such a situation had occurred in a major city, rescue teams and paramedics would arrive to the scene almost instantaneously; however, my friend wasn’t so lucky, as his unfortunate accident took place on a small F.M. road in the back country roads of central Texas. Further complicating this already frightening dilemma was the fact that the accident occurred in the wee hours of the morning. As “nightmare” like as the above dilemma sounds, luckily my friend was helped within minutes because of a S.O.S or “save our souls” system equipped in his vehicle which automatically notified emergency personnel of the location of his car and the fact that the car was involved in a major accident in which the airbags were deployed. Such technological innovations are responsible for saving millions of lives every year and are a great testament to the prowess of human ingenuity and invention. Although it took humans nearly 200,000 years to reach such levels of advanced communication, you might be surprised to know that a seemingly much less intelligent kingdom of life has been shown to exhibit levels of life-saving communication that rival even the state-of-the-art degree of communication we have at our disposal today. Given the nature of this website, you might not be surprised to know that I am referring to such communication in the plant Kingdom.

Harsh Bais and his research team at the University of Delaware have recently discovered that when injured, plant leaves can send an emergency chemical signal to their friendly neighbors to the south (the roots) requesting assistance. If a pathogen is recognized, a chemical “S.O.S” signal travels from the leaves to the roots which then secrete malic acid as a response. Malic acid has been shown to attract helpful bacteria in the soil which are then rounded up and sent to the sight of the infection to assist in combating it.

Bais, the head of the research team responsible for the findings of this study noted, “Plants are a lot smarter than we give them credit for. People think that plants, rooted in the ground, are just sitting ducks when it comes to attack by harmful fungi or bacteria, but we’ve found that plants have ways of seeking external help”.

To conduct this study, the team infected the leaves of Arabidopsis thaliana with a harmful bacterium known as Pseudomonas syringae. Not surprisingly, the infected plant’s leaves began to look ill soon after exposure to the pathogenic bacterium and so their roots were coated with an assistive microbe known as Bacillus subtilis.

Using complex biological tools, the research team was able to pinpoint a chemical “S.O.S” signal sent from the leaves to the roots of the plant, a signal whose response resulted in a release of malic acid. As noted earlier, the malic acid helped attract B. subtilis which was then sent to the site of the infection in the leaves. At the conclusion of the study, all plants initially infected with the harmful bacteria made a full and speedy recovery.

Although the research team was able to detect the chemical “S.O.S” signal, little remains to be known about exactly what this essential signal is. Perhaps future studies will reveal more information about this important clue in unraveling the complexities surrounding the surprisingly intricate system of plant communication.

News article:http://www.livescience.com/strangenews/081017-plants-cry.html
Scientific article: Plant Physiology (2008) 143:3 (Nov issue)

Question for comment: Given your knowledge of cellular response mechanisms, what sort of trigger and response system do you think is involved in the chemical “S.O.S” signal sent from the plant leaves to the roots when infection is detected?