Do plants have personalities?

Do plants have personalities?

Yes, if you use the term “personality” to refer to “the intraspecific expression of behaviors that are stable over time and consistent in different situations”, explains the ecologist richard “Rick” Karban, an international authority on plant communications and a distinguished professor in the Department of Entomology and Nematology at UC Davis.

“Individual plants react differently to alarm calls, as do individual animals,” says Karban, a 40-year-old UC Davis faculty member who has studied plant communication in sagebrush (Artemisia tridentata) since 1995 on his research site, located east of the Sierra Nevada mountain range.

In a paper recently published in the international peer-reviewed journal Oecoogia, the UC Davis professor and two colleagues found that when plants tell their neighbors – via volatile signals – that they are being attacked by herbivores , the plants showed consistent individual variation in how well they perceived and responded to cues, i.e. how effectively they bolstered their defenses.

“The gist of the argument here is that animal behaviorists have found it helpful to recognize that individual animals show behavioral tendencies that are consistent across different circumstances and repeatable over time,” Karban explained. “So, for example, some people are more daring or more timid in terms of making or responding to alarm calls. They called these individual tendencies “personalities.” We found similar consistent individual differences among mugwort plants.

The document, titled “Constant individual variation in plant communication: do plants have personalities?is co-written by Patrick Grof-Tisza from the University of Eastern Finland and Charline Couchoux from the University of Quebec. Created in 1968, Oecoogia is one of the most cited ecology journals.

“Just as animal biologists have come to view coherent individual personalities as an important factor in shaping animal phenotypes, behaviors, and interactions, so too should plant biologists include individual variation in plant communication as an attribute. important individual that influences their evolution and ecology,” they noted.

In their summary, they explained that “when animals sense danger, some people alert their neighbors with alarm calls, and the calls and responses vary systematically from individual to individual. Plants, including sagebrush, emit volatile signals when attacked by herbivores and neighbors pick up on these signals and reduce their own damage.

The researchers “experimentally transferred volatile compounds between pairs of sagebrush to assess whether individuals exhibited consistent variation in their effectiveness as transmitters and as receivers of signals, measured in terms of reduced damage from herbivores”. They found that 64% of the variance in chewing damage to branches over the growing season “was attributable to the identity of the individual receiving the cues. This variation could have been caused by inherent differences in plants as well as differences in the environments where they grew and their histories.

They found that 5% of the variance in damage caused by chewing “was attributable to the identity of the transmitter that provided the signal. This fractional variation was statistically significant and could not be attributed to the environmental conditions of the receiver. Efficient receivers were also relatively efficient transmitters, indicating consistency across different situations. Receiver and transmitter pairs that were effective communicators in 2018 were relatively effective again in 2019, indicating consistency over time. These results suggest that plants have individual repeatable personalities with respect to alarm calls.

In their paper, the scientists pointed out that the goal “in discussing plant personalities is not to insinuate that plants are people or are intelligent in the same way that we are, but to point out that animal behavior has much to offer to the development of plant biology”. . Recognizing that plants exhibit consistent behaviors that are repeatable across different situations and stable over time (i.e., personalities) has several important consequences.

First, they stated that most plant biologists focus on treatment groups rather than individuals. “The idea that individual plants can show consistent trends that can be quantified, independent of other treatments, leads to a different line of research. Additionally, the existence of plant personalities means that knowledge of an individual’s past provides information that can predict their behavior in the future. In Bayesian jargon, the existence of personalities means that informed priors can be used to improve predictive power.

Second, they wrote, “recognition of correlations between different plant behaviors suggests that there may be trade-offs between important traits that are not independent of each other. For example, a negative correlation between root and shoot growth suggests an allocation trade-off between above and below ground tissues, while a positive correlation between root and shoot growth suggests that the Differential access to resources is more important than such an allocation trade-off. Life history trade-offs of this nature are familiar to evolutionary plant biologists and this framework can be applied to other plant behaviors.

Third, they wrote, “alarm calls that affect herbivory influence plant growth, survival, and reproduction in the few systems where they have been studied. These demographic effects have the potential to shape plant adaptations, population size and distribution, ability to respond to natural and human-induced changes, and interactions with other species, although the potential effects of variation in plant communication have been largely overlooked.

The trio pointed out that “many of these volatile chemicals dissipate rapidly so that they are present in biologically active concentrations over relatively short distances (often less than 1m). In many cases, signals can be emitted unintentionally, and this process is probably best described as eavesdropping by the recipient plant.These same volatile plant signals have been found to perform other functions in some cases, such as repelling herbivores and attracting predators and pests some herbivores.

Karban is the author of the landmark book “Plant Sensing and Communication”. He is a Fellow of the Ecological Society of America (ESA) and the American Association for the Advancement of Science, and a recipient of the 1990 ESA George Mercer Award for Outstanding Research.

The UC Davis ecologist is featured in the December 23-30, 2013 edition of The New Yorker in Michael Pollan’s article, “The Intelligent Plant: Scientists Debate a New Way of Understanding Plants.” Zoe Schlanger featured it in a November 21, 2020, Bloomberg Article by Quint, “The botanist dares to ask: do plants have personalities?”

Karban, who holds a doctorate in biology from Penn, joined the faculty at UC Davis in 1982.