Development of the alpine perennial Polygonum viviparum (Polygonaceae) is characterized by extreme preformation. Four years are required for each leaf and inflorescence to progress from initiation to functional maturity. Such extreme preformation may inhibit or delay developmental and morphological responses to environmental change. This prediction was tested in natural populations using three different approaches: 1) individual plants were permanently marked and examined for among year variation in reproductive phenotype; 2) a defoliation experiment tested the capacity for plants to accelerate development of individual primordia; and 3) starch gel electrophoresis was used to identify individual ramets of clones, and phenotypic variation among physiologically independent members of a clone was examined. Results demonstrated that vegetative phenotypes are more constrained than reproductive phenotypes. Whereas defoliation did not induce any change in vegetative phenotype, reproductive phenotypes varied within individuals among years, and among ramets of individual clones. Plasticity of leaf development in P. viviparum likely is constrained by the four year duration of preformation development. In contrast, although inflorescence development requires four years, flower and bulbil (asexual propagule) development takes place only over the final two years of development (including the year of function). The shorter period of development may confer a greater ability to respond to variation. In addition, abortion of reproductive structures may provide additional phenotypic flexibility.

Key words: alpine, asexual reproduction, phenotypic plasticity, Polygonum viviparum, preformation