Intra-and inter-specific plant interactions: an experimental approach using three model species

Competition is regarded as one of the most important factors shaping dynamics, composition, and structure of plant communities. However, there is much less agreement about the mechanisms by which competition functions, and through which it is defined. We suggest that a better assessment of the relationships between plant traits, resource depletion and performance outcomes across species may provide a better understanding of the underlying mechanisms of plant interactions. Specifically, we assess the generality of competitive mechanisms by comparing intra-and inter-specific competition of three related model species: Arabidopsis thaliana (At), Anastatica hierochuntica (Ah) and Eutrema salsuginea (Es), (Brassicaceae). To achieve a better insight into plants' performance when experiencing competition, we employed phenological measurements, such as number of leaves, flowers, and above/below ground biomass as well as physiological measurements such as stomatal conductance, non-photochemical quenching and water content. Under intra-and inter-specific combinations, a decrease pattern in water content and stomatal conductance was seen in (At) and (Es) individuals. Contrarily, (Ah) showed an increase under the same conditions mentioned above. Phenological observations were more variable among the three species. A reduction on the average number of leaves and developed flowers was observed under intra-and inter-specific competition in (Es) and (Ah) individuals. Contrastively, inter-specific interactions showed only an increase in survival and fecundity in (At) at the expense of plant biomass. Under such control conditions it was difficult to find a common response of plants to their neighbors, probably because of different adaptations of the three species. Additionally, we showed that related species may employ different mechanisms for survival that engage unique plastic responses. We suggest that this study will enable us to provide a stronger theoretical basis for the study of plant interactions through an integrative approach combining ecological and physiological knowledge and, to reduce miscommunications due to different interpretation of fundamental concepts of plant ecology.