An electronic sniffer can not only determine when plants are under stress, it can also differentiate between those that have been damaged by caterpillars, mites, mildew, or by humans armed with a hole-puncher. In a new study, researcher Nigel Paul showed that an electronic nose can detect the subtle volatile organic compounds given off by plants that are under attack.
In previous experiments with artificial noses, researchers have found that they can tell the difference between champagne and other white wines, can find minuscule gas leaks in the space shuttle, and may even be able to detect the chemical compounds given off by cancer cells. But the new study, published in Environmental Science and Technology [subscription required], is the first to apply the technology to agriculture. Paul says that a number of electronic noses could be dotted around a glasshouse, checking the air for the early signs of pest attack. Portable electronic noses – about the size of a four-pack of beer – could be used to precisely locate infected plants [New Scientist].
Researchers tweaked a commercially available e-nose that has an array of sensors that react to a wide range of volatile compounds. Then they wafted streams of air over cucumber, pepper, and tomato plants that were subjected to a number of different stresses, including powdery mildew, tobacco hornworm caterpillars, and physical damage with a hole-puncher (to simulate the stress of pruning or clipping). They found that even though the e-nose hadn’t been “tuned” to pick out particular chemicals, it could easily tell the difference between plants subjected to different stresses.
Scientists have described about 1,700 volatile compounds made by different plants, a clever communication strategy for organisms that can’t move and don’t have mouths. The flirty coo emitted by a flower that’s trying to attract pollinators may be a perfume of 100 of these compounds. Plants also emit volatiles when stressed, including several rallying cries. Some of the cries stimulate production of defensive compounds in nearby plants, and others may attract enemies of the pest that is attacking the plant [Science News]. The e-nose is picking up on those subtly smelly distress cries.
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