New York, NY (October 3, 2013) – A recent issue of science magazine, Nautilus, explores the chemical codes that allow plants, including trees, to send messages to each other, especially those of their own species. This communication helps them defend against insects and other threats, and in some cases summon predators to feed on insect invaders. While we can’t hear this chatter, scientists are beginning to tap into their cryptograms, helping to understand how plants react to environmental changes, such as those expected with climate change.
The article, “Learning to Speak Shrub: Using molecular codes, plants cry for help, ward off bugs, and save each other,” presents an intriguing report on the chemical codes that help plants and trees communicate, and how scientists are using these findings to understand the impacts of higher temperatures, drought, and other environmental changes.
Plants speak in chemical codes—carbon-containing molecules called volatile organic compounds (VOCs). Characterized by the ease with which they enter the air, VOCs are a diverse group: plants alone make more than 30,000 varieties. Some VOCs produce the familiar scent of herbs or flowers, while others are released only in response to a specific cue, such as when a plant is damaged.
According to the article, “Humans don’t get much more information from VOCs. But the waves of molecules produced by a plant carry packets of cryptic messages. And just like any transmitted signals, plant-o-grams can be received, decoded, eavesdropped on, and even scrambled.”
For example, “apple trees that are chewed by spider mites send out a message that attracts other mites that eat the attacking spider mites. When female sawflies lay their eggs inside the needles of a Scots pine, the tree’s VOCs summon parasitic eulophid wasps that kill the eggs.”
Scientists warn that climate change may scramble communications, and destabilize ecosystems. Some signals may be amplified while others are dampened or never detected. Temperature changes tend to create a lot of volatility.
Higher temperatures may increase the activity of enzymes that manufacture VOC’s. And plants trying to survive droughts “will squeeze their stomata shut to prevent water loss. Leaves with closed stomata take in less carbon dioxide, which they need to manufacture VOCs. With less VOC communications, plants might not detect alarm signals and become more vulnerable to insects, or completely succumb to them.”
While plants and insects evolved to exchange these chemical messages, humans are only beginning to break the code, but to fully crack the plants’ codes, scientists will need to decipher the chemistry of whole ecosystem at one time.