Morphological Characteristics of Radical Leaves in the Serpentine Ecotype of Adenophora triphylla var. japonica (Campanulaceae) Revealed by Cultivation Experiments

ABSTRACT Several plants have adapted to serpentine soils by developing distinct morphologies. We conducted comparative morphological analyses of radical leaves through cultivation experiments to determine whether the distinctive morphology of the serpentine ecotype of Adenophora triphylla (Thunb.) A.DC. var. japonica (Regel) H. hara (Campanulaceae) is determined by phenotypic plasticity or genetically based morphological differentiation. Comparisons between the cultivated serpentine and non‐serpentine populations revealed no significant differences in radical leaf silhouette, whereas leaf size was significantly smaller in the cultivated serpentine population. Furthermore, comparisons of radical leaves between cultivated and wild populations originating from the same serpentine area revealed no significant differences in the silhouette or size of either the lamina or petiole, whereas leaf mass per area (LMA) differed significantly between the populations. In addition, the cultivated and wild serpentine populations showed more moderate increases in lamina area relative to increases in petiole traits than did the non‐serpentine population. These results indicate that the radical leaves of the serpentine populations are characterized by an overall reduction in size involving both the lamina and petiole. Furthermore, the increased LMA in the wild serpentine population may be induced by phenotypic plasticity and may contribute to water retention or a more conservative resource‐use strategy.