Stressful species interactions, such as competition and herbivory, may result in a loss of plant tissue and, consequently, in reduced reproductive output. To minimize the harmful effects of these interactions, plants rely on chemical cues in their environment to detect stressors and alter resource allocation to growth, reproduction, and defense. This study exposed plants of a single Arabidopsis thaliana ecotype (receiver plants) to volatile emissions of neighboring plants (emitter plants), which were either the same (Col-0) or different ecotype (Ler) than the receiver plants. In addition, emitter plants were either intact or damaged by larvae of the specialist herbivore Plutella xylostella. Our aim was to examine how indirect plant-plant interactions may affect the development and fitness-related traits of neighboring plants. Plant traits measured included early changes in size and trichome density, as well as plant height, biomass, and fruit set at senescence. We predict that plant-plant priming against herbivores would be more effective between emitter and receiver plants of shared ecotype than emitters and receivers with a dissimilar ecotype due to the likelihood of more similar volatile chemistry.
Results/Conclusions
Results showed that receiver plants grew significantly taller and produced significantly more fruits when exposed to intact plants of a different ecotype. In fact, fruit set was an average of sixty percent higher for plants exposed to intact emitter plants of a different ecotype compared to all other treatments. This suggests that plants may be able to use volatile cues to distinguish possible competitors of an unlike ecotype. In contrast, no differences in plant height or fruit set was observed for plants that received chemical cues from intact emitters with the same ecotype or from emitters of either ecotype that received herbivore damage. These results suggest that the effect of genetic similarity (ecotype) on resource allocation to growth and reproduction in receiver plants is dependent upon herbivory of neighboring plants. Exposure to an emitter plant of a different ecotype induced a competition-like effect; however, this effect was not maintained in the presence of herbivores. The findings of this study show that indirect, intraspecific plant interactions can have significant impacts on resource allocation and fitness, but that the outcome of these interactions is dependent on both genetic similarity and potentially stressful factors, such as herbivory.