S u m m a r y :
Plants can choose their responses to rivals—they can display decision-making skills, says a new study published in the journal Nature Communications.
Plants Choose to Attack
Plants have freedom of will—at least when it comes to dealing with their competitors. A new research, conducted by biologists from the University of Tübingen, showcases the ability of plants to choose the appropriate reaction to competitors; they do so after evaluating the latter to generate the best responses to them. This type of behaviour is normally present in animals.
Previous studies confirm how animals will choose between distinct behaviours to adopt as per the abilities of their competitors: if their opponents are comparable to them in strength, they will opt for confrontation; if they are stronger and bigger, they will go for a more passive response. In the latter case, animals will give up and not fight back, choosing avoidance or tolerance instead of confrontation.
Outgrowing Rivals or Tolerating Them?
Plants are known to have their own version of these behaviours in response to competitors. They will first have to detect competing plants in their vicinity through cues such as a decrease in light intensity resulting from other leaves blocking sunshine. Upon identifying the presence of rivals, they will react with either confrontational vertical elongation, whereby they outgrow and shade their competitors, or shade tolerance which allows them to promote their performance in conditions of limited light, or they can sometimes display avoidance behaviour, growing away from those threatening their lives. These three responses are well-documented in science, explains lead author Michal Gruntman. What has been unknown is whether the plants can decide between the options.
“In our study we wanted to learn, if plants can choose between these responses and match them to the relative size and density of their opponents,” says Gruntman.
Simulating Light Competition
The team worked on the clonal plant Potentilla reptans; they subjected it to different forms of light competition. Their findings show that P. reptans can choose its response to its competitors in an optimal manner. For instance, when it was in a scenario representing competitors that were too dense such that they could not be avoided laterally, the plant would outgrow them vertically, exhibiting the highest confrontational vertical growth. On the other hand, when it could not outgrow competitors neither laterally nor vertically, it displayed the highest shade tolerance. Then, when the circumstances were such that it could only avoid the rivals laterally, it had the highest lateral-avoidance behaviour.
These results indicate that the plant can assess the density and competitiveness of other plants, and fine-tuning its responses accordingly.
“Such an ability to choose between different responses according to their outcome could be particularly important in heterogeneous environments, where plants can grow by chance under neighbours with different size, age or density, and should therefore be able to choose their appropriate strategy,” says Gruntman.