Remember, plants are probably sensitive, too

Plants Smell

Is my ability to see more wondrous than a plant’s ability to smell? It’s more complex, certainly. But in the realm of the wondrous, should I be asking whether one is better than the other? Or should I simply see each as a marvel to be celebrated, rather than ranked?

And if I see them as marvels equally to be cherished, what happens to my place in the universe? If I no longer say, “I’m the best, most magnificent of all creations,” will I not have to abandon the belief that everything on earth is here entirely for my use. Won’t I have to value and respect other life forms for what they are, instead of what they can do for me? Won’t I have to protect them simply because they exist, because they are, like humans, wondrous?


I was launched on this train of thought by an article in New Scientist (26 Sept. 1998, pages 24-28). It reported that researchers with the U.S. government’s Agricultural Research Service in Gainesville, Florida, found that « corn, beet, and cotton leaves respond to attacks from caterpillars of the beet army worm moth by calling for help.’’

Caterpillar saliva contains a substance called volicitin, and the plant leaves react to it by secreting volatile compounds called indoles and terpenes, which evaporate and waft away. Female parasitic wasps (Cotesia marginiventris) are attracted by the scent, and lay eggs on the caterpillars. When the eggs hatch, the larvae kill the caterpillars.

However, not only wasps can smell a terpene. So can other plants. Researchers at Washington State University in Pullman previously had discovered that plants not under attack will react to the smell of a terpene, and « prepare for battle by producing chemicals that repel insects or attract predators.’’

In addition, the article says, a third group of scientists in England, at the Institute for Arable Crops Research in Rothamsted, Hertfordshire, say they have discovered a different « `wound signal’ compound that neighbouring plants can smell. The team  is keeping its identity secret until patents have been filed.’’


What links the ability of humans to see, and the ability of plants to smell, is that both functions depend on electrochemical transmissions to convey internal messages. In other words, our operating systems are based on exactly the same principles. That of humans is more complex; both are wondrous.


The New Scientist article goes on to describe other things plants do. They respond to a wider spectrum of light than we can see, enabling them to work out the length of the day, the quantity of light, and the direction from which the light is coming. This allows them to adjust their growth, for instance, directing more resources into their stems to outgrow competing plants.


Other plants forage underground, using something akin to a sense of taste to track down minerals and nutrients.


Also, it has long been known that some plants react to touch, such as the Venus flytrap, which snaps shut on visiting insects. But, according to a researcher at the University of Edinburgh, who is quoted in the article, « We now realize that plants that have developed specialized touch’’ (such as the Venus flytrap) « are amplifications of something all plants have.’’ Some use it for climbing, some for stiffening against buffeting from winds, some, such as the mimosa plant, will point their leaves downward at the slightest contact.


And, of course, the folk tales are true: plants do hear. The article reports that research at Wake Forest University in North Carolina found that plant growth doubled when exposed for lengthy periods to sound in roughly the same range as a human voice, and at 70 to 80 decibels, « which is a bit louder than speaking.’’


In a society bent on quantifying and rating everything, such as ours, it’s difficult to find space for wonder. But the next time you stop to smell the roses, just think: they may be smelling you back.

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