A latitudinal cline and response to vernalization in leaf angle and morphology in Arabidopsis thaliana (Brassicaceae).

Adaptation to latitudinal patterns of environmental variation is predicted to result in clinal variation in leaf traits. Therefore, this study tested for geographic differentiation and plastic responses to vernalization in leaf angle and leaf morphology in Arabidopsis thaliana. Twenty-one European ecotypes were grown in a common growth chamber environment. Replicates of each ecotype were exposed to one of four treatments: 0, 10, 20 or 30 d of vernalization. Ecotypes from lower latitudes had more erect leaves, as predicted from functional arguments about selection to maximize photosynthesis. Lower-latitude ecotypes also had more elongated petioles as predicted by a biomechanical constraint hypothesis. In addition, extended vernalization resulted in shorter and more erect leaves. As predicted by functional and adaptive hypotheses, our results show genetically based clinal variation as well as environmentally induced variation in leaf traits.