Habitat exploration through morphological plasticity in two chalk grassland perennials

Rhizome lengths and degree of rhizome branching in clonal perennial plants may change in response to environmental conditions, enabling plants to more efficiently capture unevenly distributed resources (so-called "foraging' responses). Such components of plant growth were investigated in Carex flacca and Brachypodium pinnatum. Mean rhizome length in Brachypodium was significantly smaller under high nutrient availability, but only when unshaded. Carex produced longer rhizomes under high light conditions, but showed no effects of nutrients. In both species, branching was greater under higher levels of light intensity, and with more favourable nutrient conditions. Shoots of both species increased in height in response to shading, but only shoots of Brachypodium responded to fertilization. As Carex does not produce shorter rhizomes under more favourable conditions, the foraging model is inapplicable. Growth responses of Brachypodium were in better agreement with the foraging hypothesis, but the amount of endogenous variation in rhizome length and bud dynamics overrides the plastic changes in response to different resource supply. -from Authors