Effects of Tiller Separation and Root Pruning on the Growth of Lolium perenne L.

Experiments have been carried out to assess the role of inter-tiller interactions within plants of Lolium perenne L. cv. S24 as factors which could play a part in determining the growth-rate of the whole plant. In order to do this, the effect of tiller separation on plant growth was studied as well as the influence of the removal of different parts of the root and shoot system. Whenever plants were supplied with nutrients by means of culture solutions, separation of tillers brought about a marked increase in the amount of dry matter produced. Root pruning and in particular the removal of root apices brought about similar increases in growth. Separation of tillers in soil-grown plants did not bring about increased growth. These results are interpreted as indicating that separation of tillers or the initial removal of root apices in plants supplied with nutrients by means of culture solution, promotes root branching which brings about an increased net assimilation rate arising from an increase supply of a growth-promoting substance, probably a cytokinin, from the root apices. The results are not taken as indicative of an intertiller interaction which restricts the growth of intact plants.