We know that plants communicate. Childhood fairy tales taught us this way back in the day. And, in the last four or so decades, hard core, just-the-facts-ma’am researchers have proven that plants of all sorts, from weeds to willows, have means of transmitting chemical signals in order to attract pollinators or defend against predators. But now we can actually see this remarkable process as it happens and understand how signals are shared between plants.

A summer flower meadow along the Elk River near Fernie, B.C.

A new study published just this past October reveals how plants can signal danger and they captured the process on camera. I urge you to take a moment to check out the paper. Don’t let the title–Green Leaf Volatile Sensory Calcium Transduction In Arabidopsis–put you off. BTW: Arabidopsis is rockcress, a small plant in the mustard family.

In order for the researchers to be able to see and track the plants’ responses ‘on film’ so to speak, they had to genetically modify the plants they were studying (mustard and tomato plants) so that the calcium ions within the leaves of the plants would fluoresce. Why calcium ions? Calcium signalling is part of how cells function, even in humans.

What this team of researchers have done is extraordinary and, yup, I can barely wrap my head around what they’ve accomplished much less explain it to anyone else. But, if you’re interested, the Washington Post has a wonderfully easy to understand article that covers the whole thing entitled How Plants Communicate With Each Other When In Danger.

And what are they saying?

Plants emit chemicals called Volatile Organic Compounds and–this is really cool–we humans can smell them. The VOCs in the scent of a rose attract pollinators. The VOCs in the scent of a ripe apple attract predators of insect herbivores. For instance, the apple’s fragrance can appeal to birds who then arrive and eat the bugs that might otherwise damage the apple.

And what do plants have to say to other plants? When an injured plant emits certain chemicals, healthy plants can sense this (the research paper shows exactly how) and start up their own defense mechanisms such as producing chemicals that can deter the bad bug that’s wreaking havoc at the moment.

Any plant that has leaves emits a class of VOCs called Green Leafy Volatiles. Whenever a plant registers injury in its leaves it/they will emit GLVs and we can smell these volatiles, too. So the next time you inhale the fragrance of freshly cut grass keep in mind that what you’re receiving are signals sent by the grass that the grass blades have been injured.

Kind of puts a whole new spin on that classic summer-time scent.