How Plants Defend Themselves

Maybe it’s time to reconsider what we think about plants: They hear, touch, see and even “talk” in order to survive.
April/May 2013
http://www.motherearthnews.com/nature-and-environment/how-plants-defend-themselves-zm0z13amzcom.aspx
Broccoli no more aspires to sizzling in a stir-fry than pigs dream of becoming ham.


Illustration By Brad Anderson

The more researchers study the science of plants, the more remarkable those chlorophyll-filled wonders seem to be. If your definition of ethical eating involves dining only on non-sentient plants, you might rethink your food choices. Tomatoes, Brussels sprouts and other members of the plant family are lively, highly reactive to their environments and, in a variety of ways, communicate with the world around them. This excerpt is taken from “Sorry Vegans: Brussels Sprouts Like to Live, Too,” first published in The New York Times. — MOTHER EARTH NEWS  

When plant biologists speak of their subjects, they use active verbs and vivid images. Plants “forage” for resources such as light and soil nutrients, and “anticipate” rough spots and opportunities. By analyzing the ratio of red light and far red light (light at the far end of the spectrum) falling on their leaves, for example, plants can sense the presence of other chlorophyllated competitors nearby and try to grow the other way. Their roots ride the underground rhizosphere and engage in cross-cultural and microbial trade.

“Plants are not static or silly,” says Monika Hilker, Ph.D., of the Institute of Biology at the Free University of Berlin. “They respond to tactile cues; they recognize different wavelengths of light; they listen to chemical signals; they can even talk (via chemical signals).” Touch, sight, hearing, speech: “These are sensory modalities and abilities we normally think of as only being in animals,” Hilker says.

Plants can’t run away from a threat, but they can stand their ground. “They are very good at avoiding getting eaten,” says plant geneticist Linda Walling, Ph.D., of the University of California, Riverside. “It’s an unusual situation where insects can overcome those defenses.” At the smallest nip to its leaves, specialized cells on the plant’s surface release chemicals to irritate the predator or sticky goo to entrap it. Genes in the plant’s DNA are activated to wage systemwide chemical warfare, the plant’s version of an immune response. We need terpenes, alkaloids, phenolics — let’s move! 

“I’m amazed at how fast some of these things happen,” says Consuelo De Moraes, Ph.D., of Pennsylvania State University. De Moraes and her colleagues did experiments to clock a plant’s systemic response time and found that, in less than 20 minutes from the moment a caterpillar began feeding on its leaves, the plant had plucked carbon from the air and forged defensive compounds from scratch.

Just because we humans can’t hear them doesn’t mean plants don’t howl. Some of the compounds that plants generate in response to insect mastication — their feedback, you might say — are volatile chemicals that serve as cries for help. Such airborne alarms have been shown to attract both large, predatory insects such as dragonflies, which delight in caterpillar meat, as well as tiny parasitic insects, which can infect a caterpillar and destroy it from within.

Read the full article: Sorry, Vegans: Brussels Sprouts Like to Live, Too.  


This excerpt has been reprinted with permission, © 2013 The New York Times.