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.

  • stubborn broccoli plant
    Broccoli no more aspires to sizzling in a stir-fry than pigs dream of becoming ham.
    Illustration By Brad Anderson
  • seedlings illustration
    Seedlings of parasitic dodder plants scout for volatile chemicals released by a potential host, such as the tomato, then put out tendrils to slowly encircle their victim and suck out its life.
    Illustration By Brad Anderson
  • plants call for backup
    Some plants "call" for backup whenever they're attacked.
    Illustration By Brad Anderson

  • stubborn broccoli plant
  • seedlings illustration
  • plants call for backup

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.

5/28/2016 7:09:46 AM

I wonder what type of defense a plant launches when it is attacked by roundup. Wheat sprayed before harvest must change the grain to defend itself from roundup but we humans get the results of the attack. This defending attack plus the roundup is probably the reason there is so much gluten or wheat problems. Eric

5/15/2013 2:54:52 PM

Very interesting!


5/8/2013 5:31:09 AM

I made my first loaf of bread today using the 'fridge method'....but I only use sourdough starter for the yeast...have been making kneaded sourdough bread for quite a long time....i put the pizza stone in the oven then turned it on to 230 deg celcius, then put the ball shaped dough straight from the fridge after shaping it, onto the stone so that it could rise gently as the oven heated up....also put a seperate dish of boiling water in the bottom of the oven once temp was reached and also timed 40 mins from when temp was reached....the bread doubled in size, had a crisp, brown outside and a lovely moist inside...truly a FABULOUS loaf of bread....oh...and I only used 3 teaspoons of salt....and it was great....I felt 3 tablespoons was too much....and another onus...husband declared it VERY GOOD too....that's a first.

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