Differences in resource allocation to stolon branches of Kopu white clover genotypes induced by manipulation of rooting

Abstract

White clover (Trifolium repens L.) genotypes of the cv. Grasslands Kopu which had differing numbers of vascular bundles within their stolons were tested for potential for resource sharing between shoot branches on either side of parent axis. Genotypes with a high (10-13) number of vascular bundles (H-genotypes) had larger leaves, thicker stolons but lower node appearance rates than genotypes with a low (8-9) number of vascular bundles (L-genotypes). In the first experiment all roots on one side of the parent axis were severed two days before plants were labelled with 32P (uptake period 24 h). In H-genotypes, distribution of radioactive phosphorus (32P) exported from a nodal root was restricted largely to near-side branches, i.e. branches which were on the same side of the parent axis as the source root, with only 4% allocated to far-side branches. In contrast about 20% of 32P exported from the source root was transported to far-side branches in L-genotypes. In the second experiment, where all far-side roots were severed three weeks before harvest, growth of far-side branches was similarly reduced in L-genotypes and Hgenotypes. When root formation along one side of the parent axis was prevented during the entire experimental period the mean ratio of total dry weight between nearand far-side branches was higher in H-genotypes compared to L-genotypes. Keywords: branch development, nutrient distribution, phosphorus, vascular bundle, white clover, Trifolium repens L.