Autoradiographs were made of plants of Lolium multiflorum Lam. after 14CO2 had been fixed by selected leaves. The results showed that labelled compounds were not translocated to other tillers but were moved to the whole root system. This pattern of distribution was changed when all or some of the tillers on the plant were defoliated. Where a single undefoliated tiller remained, it initially supplied the cut tillers with 14C-containing products, thus reintegrating a system of apparently independent tillers. When all the tillers were partially defoliated, labelled compounds were no longer translocated to the root system. A further experiment suggested that root reserves were not mobilized for regrowth following defoliation. These results are discussed in terms of the integration of a grass plant in the vegetative state.