Physiological and genetic analyzes of population differentiation in plants in relation to life cycle regulation mechanisms.

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(1). We clarified the mechanisms of population differentiation in Cardamine flexuosa (Cruciferae) collected from various habitats in Japan in relation to these characters of life cycle regulation based on developmental and genetic analyzes.(2). The research was planned on three parts as follow : (i) Photoperiodic requirement for flowering under natural alteration of daylength at Sendai (38.16 N.140.54E), (ii) Physiological analyzes of the life cycle regulation depending on combinations with photoperiods and chilling treatments under completely regulated environments, (iii) Genetic analysis of the populations appeared from similarities of zymograms in various isozymes tested.(3). Populations located at higher latitude showed tightly a long-day required flowering, meaning to be useful preparing high tolerant individuals for dry and cold conditions in winter. Populations at lower latitude, inversely, showed a size dependent flowering because of relatively mild environmental selective pressure.(4). Yonakuni population located 24.98 N being the lowest latitude showed very severe regulation whick suppressed the germination with higher temperature refimes. However, no temperature control for germination observed for population located at higher latitude.(5). Genetic similarities in relation to latitudinal habitats were found in isozyme analysis, especially among populations located beyond 38 N to north which showed strong photoperiodic dependency to flowering. But the same genotypes were also observed in other populations far from the latitude.(6). In conclusion, the life cycle was regulated in switching growth phase from vegetative to reproductive by photoperiodic response in higher latitude populations, but no control in germination process. On the other hand, it was regulated in switching on or off germinating procedure by temperature in lower latitude populations, but completely no control in developmental switching.