Plants do not warn each other for approaching danger via an underground network, but they do use that network to listen to each other. This is evident from a new study from the University of Oxford and the VU University Amsterdam that was published in the scientific journal Proceedings of the National Academy of Sciences.
Scientists have long been aware of an underground network that connects plants. Through a symbiotic collaboration between fungi and the roots of the plants, also called Mycorrhiza, something like the wood wide web. Earlier it was shown that plants can send raw materials and information through that network. For example, scientists discovered that when a plant is attacked by a herbivorous or pathogen, other plants in the network put their defense mechanisms on sharply. But how exactly that communication goes was unclear until recently.
According to scientists, the fact that plants would actively inform each other would contradict evolutionary theory. It suggests that such a behavior is only promoted when there is an advantage for the transmitter and the recipient of such a signal. The researchers therefore faced a mystery: why would a plant that are being attacked signals to warn its neighbors?
To find out that, a team from the universities of Oxford and Amsterdam used mathematic models to go through all possible scenarios. They discovered that it is extremely difficult to find situations in which plants would have been evolutionally selected to warn their peers about an imminent attack. Because plants compete with their neighbors for sunlight and nutrients. So they do not benefit from helping their neighbors. The results of the study even indicate in the completely reverse direction. Plants would benefit from sending unfair signals to their neighbors in an attempt to harm a nearby plant.
“Our results indicate that it is more likely that plants are deceptively behaving in relation to their neighbors, rather than altruistic,” says the Thomas Scott study. “For example, plants can signal that a herbivore is being attacked, even if there is no herbivore present. Plants can take advantage of unfair signaling because it harms their local competitors, by tempting them to invest in expensive defense mechanisms against herbivores. ”
Fungi
The researchers therefore had to look for a different hypothesis. The mathematical models led the scientists to two feasible alternatives. Plants may not be able to suppress that they send a signal when they are attacked, even if they do not want to pass on that information to their neighbors. Whether it is an option, according to the researchers, that the fungi keep an eye on their guest plant and they broadcast the signal when it is attacked. That scenario is interesting for the fungi, because they do get an advantage from protecting all the plants with which they are connected.
“Our results indicate that it is more likely that plants are deceptively behaving in relation to their neighbors, instead of altruistic”
Thomas Scott
Main author Study
“Perhaps it is the fungal networks themselves that issue the warning signals,” says Scott. “Mycorrhiza fungi depends on the plants in their network for carbohydrates, so it is important to keep these plants in good condition. Perhaps the fungi listen to their plant partners, detect them when one has been attacked and they warn the others to prepare. ”
“There is no doubt that information is being transferred,” adds co-author Toby Kiers from the VU University Amsterdam. “Organisms constantly detect and process information about their environment. The question is whether plants actively broadcast signals to warn each other. Perhaps one plant, just like gossiping neighbors, just listens the other. “