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-tillerinteractions within plants of Lolium perenne L. cv. S24 as factorswhich could play a part in determining the growth-rate of thewhole plant. In order to do this, the effect of tiller separationon plant growth was studied as well as the influence of theremoval of different parts of the root and shoot system. Wheneverplants were supplied with nutrients by means of culture solutions,separation of tillers brought about a marked increase in theamount of dry matter produced. Root pruning and in particularthe removal of root apices brought about similar increases ingrowth. Separation of tillers in soil-grown plants did not bringabout increased growth. These results are interpreted as indicatingthat separation of tillers or the initial removal of root apicesin plants supplied with nutrients by means of culture solution,promotes root branching which brings about an increased netassimilation rate arising from an increase supply of a growth-promotingsubstance, probably a cytokinin, from the root apices. The resultsare not taken as indicative of an intertiller interaction whichrestricts the growth of intact plants.