In response to mechanical stimulation in plants, the activity of a number of genes changes rather rapidly
Although we know that the plants are alive, it is still difficult for us to imagine that they are feeling something - if a plant clicks on a leaf, it will not pull back the branch and run away. There are some exceptions - for example, some carnivorous plants that feel very well mechanical irritation from a potential victim, but one way or another, we consider plants to be somewhat insensitive - neither sense organs, like those of animals, nor the nervous system They dont have.
However, in fact, plants feel everything, even if they do not show it outwardly. Researchers at the University of Western Australia have found that in response to water spraying, Arabidopsis thaliana leaves change the activity of many genes that control mitochondria and chloroplasts.
Everything really looked as if Arabidopsis reacted precisely to the touch of water droplets (the same was observed when the leaves were touched with tweezers or when they were lightly patted): in an article in Plant Physiology, the authors write that the molecular response was different, than when the plant was acted upon with a chemical irritant. A mechanical reaction occurred after 10-30 minutes; at the same time, curiously, similar changes occurred if a shadow suddenly fell on the leaves, as if someone approached the plant - such a sharp shadow, obviously, served as a signal that someone would touch the leaves, and good, if just some passer-by, and not someone herbivore.
It was also possible to identify two genes that trigger molecular rearrangement after mechanical stimulation, AtWRKY15 and AtWRKY40 - their task, apparently, is to assess how serious the "threat of touch" turned out to be and whether it is worth returning back to normal.
In fact, biologists have long known that mechanical stimulation suppresses plant growth - in 2000, researchers from Rice University reported that if a plant is regularly touched, it grows more slowly and grows very small. In a relatively recent article in Current Biology, the same authors wrote that one of the components of the plant's mechanical sense could be the hormones jasmonates. They influence a variety of processes, from individual plant development to pest control.
It was found that when the level of jasmonates rises, metabolites accumulate in plant tissues, literally causing indigestion in insect pests. In addition, jasmonates help not only against insects, but also against some fungal infections. On the other hand, as it turned out, their concentration in plant tissues increases under mechanical action. It is easy to imagine that in this way the plants are protected from the invasion of caterpillars: the more insects crawl on them, the stronger the mechanical irritation, the more protective hormones are produced.
Aside from mechanical sensitivity, we can recall that, for example, goldenrod senses flies that lay their eggs on it by smell, and in response emits its own odor signals to scare away insects. Three years ago, researchers from the University of Pennsylvania wrote to PNAS about this - however, the authors of the work did not offer any explanation of how exactly goldenrod can sense the pheromones of flies.
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Plants can even warn neighbors of danger: recently, biologists from the University of California, Davis discovered that when someone starts eating wormwood, it releases volatile substances that its neighbors catch and in response synthesize some substances that make them less tasty. Curiously, only a close relative will understand the signal - if the wormwood neighbor was genetically very different from the one in trouble, the distress signal passed by him.
Kirill Stasevich