XVI International Botanical Congess

We have been studying the developmental basis and adaptive significance of variation in flowering time in annual plants. We propose a framework in which flowering time is related to three types of Astructural elements@ of plant construction: (1) meristem fates, (2) developmental rate or size of metamers, and (3) plant metabolism. The structural elements affect other important fitness components, e.g. plant architecture, growth rate, and breeding system. As a result, selection on flowering time is a function of (a) the links between structural elements and multiple fitness components, and (b) the links between fitness components and fitness. Both sets of links may differ across environments. We report on studies of structural element variation and selection in two annual species (Polygonum, Clarkia) that address the adaptive significance of early vs. late flowering in stressful vs. benign environments.