The influence of Rhizobium trifolii on growth characteristics of Trifolium repens: integration of local environments by clonal genets of T. repens

Abstract

Seven replicate clones of Trifolium repens were each grown such that the two halves of each clone were growing in different environments, one half in sterilized soil with an added inoculum of Rhizobium trifolii, and the other in sterilized soil without the inoculum. In one block, the two halves of the clone remained connected, while in the other block, the two halves were severed. For all measured characters there were no significant differences between connected and severed clones. Two responses to the presence of Rhizobium were detected. First, the half clone with Rhizobium grew faster and produced more leaves, longer stolons, more new ramets, and had a greater dry weight than the other half of the same clone, either connected or severed, growing without Rhizobium. Secondly, there was a significant increase in the percent branching of nodes along the main stolon, thus altering the form of the half clone growing with Rhizobium; other within-clone characteristics did not change. These responses are discussed in the context of the ecological and evolutionary benefits and costs of integrating environmental differences experienced by the same clone.