Physiologically-mediated self/nonself root discrimination in Trifolium repens has mixed effects on plant performance

Recent studies suggest that plant roots can avoid competition with other roots of the same plant, but the mechanism behind this behavior is yet largely unclear and their effects on plant performance hardly studied. We grew combinations of two ramets of Trifolium repens in a single pot that were either intact, disconnected for a shorter or longer time, or that belonged to different genotypes. Interconnected ramets developed lower root length and mass than any other combination of ramets, supporting the notion that self/nonself discrimination in T. repens was based entirely on physiological coordination between different roots that develop on the same plant, rather than biochemical allorecognition. These responses were consistent among eight field-collected genotypes, suggesting that self/nonself discrimination is a common feature in wild populations of white clover. There were no significant treatment x genotype interactions suggesting that genetic variation for self/nonself discrimination may be limited. Self-interactions resulted in lower to similar shoot biomass and number of ramets, but higher flowering probabilities, compared to nonself interactions. Thus, our results demonstrated that the performance consequences of self/nonself discrimination may be more complicated than previously thought.