Morphological and Anatomical Variations in Rheophytic Ecotype of Violet, Viola mandshurica var. <i>ikedaeana</i>(Violaceae)

We compared the leaf morphology and anatomy of the putative rheophytic ecotype of Viola mandshurica W. Becker var. ikedaeana (W. Becker ex Taken.) F. Maek. and its closely related variety, V. mandshurica var. mandshurica. We showed that the leaf of the rheophytic ecotype of V. mandshurica var. ikedaeana was narrower than that of V. mandshurica var. mandshurica. Moreover, the leaf thickness and guard cell size of the rheophytic ecotype of V. mandshurica var. ikedaeana were significantly larger than those of V. mandshurica var. mandshurica. We further showed that leaves of the rheophytic ecotype of V. mandshurica var. ikedaeana contained fewer cells than did those of V. mandshurica var. mandshurica. Our results suggest that the narrower leaves of V. mandshurica var. ikedaeana are caused by a decrease in the number of cells. A narrower leaf may enable the rheophytic ecotype of V. mandshurica var. ikedaeana to resist the strong flow of water that occurs after heavy rainfall, while a thicker leaf may enhance tolerance to desiccation and high- intensity light.