Influence of Position and Number of Nodal Roots on Outgrowth of Axillary Buds and Development of Branches in Trifolium repens(L.)

Abstract

The implications of the presence of a root, either at the parent node or at neighbour nodes, on branch formation of Trifolium repens(white clover) was investigated. Plants were freely rooted or rooting was restricted to every sixth or every twelfth node along the parent axis. The absence of a root at the parent node had little influence on the probability of the subtending axillary bud forming a branch but, on average, delayed the outgrowth of the bud. The probability that an axillary bud, emerging from a non-rooted parent node, developed to a lateral branch (branch with elongated internodes) decreased with decreasing proximity of the parent node to a rooted node. Lateral branches emerging from non-rooted parent nodes which were two nodes distal to a rooted node had a higher rate of node appearance, a greater mean internode length and area per leaf, and were more branched than lateral branches emerging from other non-rooted parent nodes. The dry mass of each single root and of branches grown at rooted parent nodes were significantly higher in plants with restricted rooting than in freely rooted plants. Restriction in the number of rooted nodes per plant increased the number of inflorescences. It is concluded that the whole plant response to restricted root formation was continuous growth of the parent axis and compensatory growth of the branch at the rooted node. In general, growth was slow for axillary buds whose development was dependent on the basipetal movement or cross-transport within the stolons of resources exported from roots.