PHENOTYPIC PLASTICITY IN CARDAMINE FLEXUOSA - VARIATION AMONG POPULATIONS IN PLASTIC RESPONSE TO CHILLING TREATMENTS AND PHOTOPERIODS

Variability in the plastic responses of seven life history traits to d ifferent chilling and photoperiod regimes was studied in four wild pop ulations of Cardamine flexuosa. This species, a winter-green or year-l ong annual; showed a facultative long-day and chilling requirement for flowering. Considerable variation among populations was noted in plas ticity of all traits. Differences in plasticity were greater among thr ee paddy field populations from different climatic areas than between adjacent populations under different disturbance regimes. A paddy fiel d population (OP) and an adjacent orchard population (OG) exhibited si milar plasticity, in both amounts and patterns of response. TP, a Japa n Sea coast population, was distinct from three other populations, esp ecially in the small amounts of plasticity. Differences in amount of r esponse were much more common than differences in pattern of response. Character expressions of five traits were significantly correlated wi th the number of days to flowering. Days to flowering and the numbers of inflorescences and siliques showed high negative correlations becau se the branching ability of meristems decreased with delay of flowerin g.