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

Abstract

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 highintensity light.

Rheophytic Adaptation of Eurya Japonica Thunb. (Ternstroemiaceae)

“…Our results indicated that the stomatal density of riverside populations was significantly higher than that of the inland populations (Table 5). The increase in stomatal density was not, however, a specific differentiation, and some similar cases have been reported in rheophytic adaptation of various angiosperms (Nomura et al, 2006;Ueda et al, 2012;Matsui et al, 2013). Some studies have indicated that changes in stomatal density in response to soil moisture appears to correspond to environmental conditions (Bakker, 1991;Miyazawa, Livingston, & Turpin, 2006;Xu & Zhou, 2008;Sun, Yan, Cui, & Liu, 2014), and several approaches to improve water-use efficiency through the modification of stomatal traits have been tested in model plants (Büssis, von Groll, Fisahn, & Altmann, 2006;Liu, Ohashi-Ito, & Bergmann, 2009;Dow, Berry, & Bergmann, 2014;Dittberner et al, 2018).…”

“…ikedaeana, and Farfugium japonicum var. luchuence had thicker leaves than those of closely related dryland species of R. macrosepalum, V. mandshurica, and F. japonicum, respectively (Nomura, Setoguchi, & Takaso, 2006;Ueda et al 2012;Matsui et al 2013). Therefore, the thick leaves induced along rivers were the general tendency in rheophyte plants because this modification was common to different plant lineages.…”

“…This anatomical differentiation of the rheophytic E. japonica was similar to that of R. indicum f. otakumi, R. ripense, and V. mandshurica var. ikedaeana (Setoguchi & Kajimura, 2004;Ueda et al, 2012;Matsui et al, 2013), although Dendranthema yoshinaganthum, As. microcephalus var.…”

“…F. Maek. (Violaceae) were also induced by a decrease in number of cells (Matsui et al, 2013). Although their narrow lanceolate or cuneate leaves were formed by changes in the number of leaf cells, Tsukaya (2002a) and Yamada et al (2011) reported a variation in leaf width in the rheophyte Dendranthema yoshinaganthum (Makino ex Kitam.)…”

“…In addition to cell size and number of leaves, some anatomical studies reported that rheophytic species had seen an increase in their stomatal size density, suggesting that they had differentiated the use of solar radiation and water for photosynthesis from closely related inland species (Ohga et al, 2012;Ueda et al, 2012;Matsui et al, 2013). These observed morphological and anatomical traits of rheophytic species could be explained by certain aspects of the riparian environment, such as high irradiation and frequent flooding after heavy rainfall-to which they were exposed.…”