There’s a Surprising Lot More to Plants Than We Realize

Fagjun | Published 2018-01-10 16:11

Plants can make decisions and learn, which is pretty impressive for organisms that don’t have a brain. Scientists have now gained more insight into the way plants make decisions when under pressure and placed in a competitive situation.


Plants are able to make decisions that benefit their survival.

Plants are able to make decisions that benefit their survival.

 

Many of us probably don’t think of plants as capable of doing things that we and other animals can do, which is to learn and make decisions based on the available information. However, to think that way is to severely underestimate what plants are capable of. Plants, it turns out, do indeed do more than just grow.

 

Just like any other living organism on Earth, plants have a variety of options when it comes to ensuring their survival. According to a new study, plants are able to base their decisions for their survival on the the competitive ability of other plants surrounding them. Doing so allows them to choose between different strategies in order to be able to survive.



Survival Responses


Potentilla reptans [Photo by Olivier Pichard]

Potentilla reptans [Photo by Olivier Pichard]

 

Animals usually choose between behaviors like confrontation, avoidance, and tolerance when it comes to dealing with competition. Take for example the competition between a small animal and a much bigger animal. If the smaller animal wanted to survive, it would be best if it chose avoidance or tolerance instead of confrontation, which can decrease its chances of survival.

 

A new study has found that plants—Potentilla reptans in particular in the case of the study—can also assess the size and strength of their neighbors so they can make decisions accordingly. Plants use cues like changes in light quantity and red to far-red wavelengths (R:FR) to figure out if there are other plants close by. These cues trigger two types of responses: the plants either try to grow taller than their neighbors (confrontational vertical elongation), or they go into survival mode (shade tolerance), in which the plants adapt to limited light. Some plants exhibit a third type of response: growing horizontally away from their neighbors (avoidance behavior).

 

"These three alternative responses of plants to light competition have been well-documented in the literature," says Michal Gruntman, one of the researchers. "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."



Experiments


The experiment setup [Image by the University of Tübingen]

The experiment setup [Image by the University of Tübingen]

 

The researchers found the answer they needed: yes. Yes, plants are indeed able to choose between the three aforementioned options. The researchers came to this conclusion by performing a series of experiments that intend to mimic different light competition situations. In order to mimic neighboring vegetation, the researchers surrounded plants with transparent green filters shaped into vertical stripes. By manipulating the height and density of these stripes, the researchers were able to simulate different competition scenarios for the plants.

 

Apparently, Potentilla reptans was indeed able to optimize its chances of survival by making decisions based on what its competitors are like. When the researchers made Potentilla reptans think that it was surrounded by shorter but denser neighbors, it decided on confrontational vertical elongation. When it thought that it had tall competitors, it went into shade tolerance mode. Lastly, when the plant thought it had tall but sparse neighbors, it decided on avoidance behavior.

 

Of course, the only resource that the research tackled is light. It’s still unknown if plants react in the same way to competition for other resources, such as those that impact roots. This is what researchers want to find out next.

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