Life history and plant architecture: size-dependent reproductive allocation in annual and biennial Centaurium species

The frequency of annuals, monocarpic perennials and polycarpic perennials among the dicotyledonous, herbaceous representatives of the European plant families are compared and related to various characteristics of plant architecture. It is suggested that the evolution of life-history may be governed by plant architecture. A comparison between annual and biennial Centaurium species suggests that the selective advantage of bienniality could relate to the production of a large stem within a short period. The typical architecture of a monocarpic perennial does not automatically imply an allometric relation between seed production and plant size. Size-dependent seed allocation, when present, is due to disproportionality between the plant’s size and the amount of resources available for reproductive allocation, and not to the size constraints imposed by the plant’s architecture. The evolution of monocarpic perenniality is therefore not a simple allometric step. Interpopulation differences in seed allocation may arise from differences in the nature or the availability of that particular resource that limits the reproductive allocation of biomass, and do not necessarily reflect differences in partitioning strategies.