Instead of talking to the trees, try cuddling your favourite geranium.
While flowers and other members of the plant kingdom seem not to complain when we pinch their buds or step on them, they are fully aware of what's happening and rapidly respond to the way they're treated, scientists have discovered.
The research, published in the respected journal Plant Physiology, reveals that plants react in various ways when patted or touched – and may even flower differently or develop greater resistance to pests.
"We've found that even the simple act of water droplets landing on a leaf causes an elaborate response inside of plants," said lead researcher Dr Olivier Van Aken of the University of Western Australia's ARC centre of excellence in plant energy biology. "The same goes for the wind blowing, an insect moving across a leaf or even clouds casting a shadow over a plant."
It's also been shown that the vibrations of something a small as a caterpillar chewing on a leaf, for instance, are passed on to more distant parts of the plant to elicit a response. "But, as yet, there's no evidence to back the idea held by some people that the vibrations caused by just talking to plants has a strong enough effect to move plants," Dr Van Aken explained.
The study suggests that the touch response may prepare plants to defend themselves from danger or to take advantage of favourable changes in the weather.
"While nothing very obvious happens to plants when they are touched, their physiological response launches a cascade of signals inside leaves that prepare them for the future," Dr Van Aken said.
A change in the expression of thousands of plant genes was initially observed by researchers when plants were sprayed with water. This occurred within minutes of spraying and stopped about half an hour later.
"We were able to show that this response was caused not by active compounds in the spray but by the physical contact from water drops landing on the leaf surface," said Dr Van Aken.
Curious as to what was happening, the researchers examined what else could trigger such a response. They found the results could also be produced by gently patting plants by hand or by touching them with tweezers. A similar response was triggered by shadows falling suddenly over plants, restricting the light received.
"Unlike animals, plants cannot run away from harmful conditions," said Dr Van Aken. "Instead, they've developed intricate stress defence systems to sense their environment and help them detect danger and respond appropriately."
The study also identified two proteins, AtWRKY15 and AtWRKY40, which help switch off the plant's touch response. "Switching off the response signal is very important," Dr Van Aken said. "It allows plants to get on with life as normal, forgetting about the signal and treating it as a false alarm."
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