Persistency of plant growth is closely related to the manner of resource allocation; however, plants often shift the pattern of resource allocation depending on their growth condition. We examined how the plants with different levels of persistency change their resource allocation patterns in response to defoliation using three Lolium species: L. temulentum (annual); L. multiflorum (predominantly annual but occasionally overwinter); and L. perenne (perennial). We subjected the plants to clipping treatment by excising approximately 70% of the aboveground body parts of the plants from the three species, and compared the growth pattern of clipped plants with that of the intact controls. Lolium species with different persistency have developed different reaction norms for resource allocation to clipping treatment. After clipping, L. temulentum and L. multiflorum maintained the proportion of reproductive tillers and seed productivity resulting in an increase in the resource investment in the development of reproductive parts, which was compensated with the loss of allocation to the development of vegetative parts. Annual species, which can propagate themselves only through seed generation, possibly enhanced seed production to ensure regeneration under undesirable condition at the cost of vegetative growth. In contrast, L. perenne invested more resources in foliage development by reducing seed production in response to clipping treatment. Perennial plants that can endure adverse effects possibly allocate substantial portion of the resources to vegetative growth for ensuring survival. L. multiflorum showed similar regrowth habits with respect to the constant foliage and seed production per panicle as those of L. perenne, but differed from those of L. temulentum. This may be because the two former species have common ancestors.
