Rheophytic Adaptation of Eurya Japonica Thunb. (Ternstroemiaceae)

Abstract

Plants along rivers have narrow leaves to avoid the stress caused by the river’s flow during flooding. Plants that have undergone such morphological leaf modifications to adapt to rivers are called rheophytes. Some populations of Eurya japonica Thunb. (Ternstroemiaceae) were grown on riversides so that the comparative morphology and anatomy of leaves between riverside and inland (control) populations could be examined to confirm their rheophytic speciation. Our morphological and anatomical analyses revealed that the leaf of E. japonica in the riverside populations was significantly smaller than that of the inland populations due to the decreased number of cells; therefore, the pattern of rheophytic differentiation in riversides was not the stenophyllization but the miniaturization of the leaf. Moreover, our results indicated that this species in the riverside populations had thicker leaves and higher density of stomata than those of inland populations, suggesting that E. japonica had been morphologically modified in response to the light and water environments along the river.

Adaptative Leaf Morphology of Eurya japonica Thunb. (Ternstroemiaceae) in Serpentine Areas

“…In addition, future comparative studies of morphological and anatomical modifications of other organs, such as stem and root, between inland areas and serpentine areas will boost up our understanding of the adaptation of E. japonica into serpentine areas. Shiba et al (2021) indicated that six independent riverside populations of E. japonica experienced differentiation, including smaller leaves and higher stomata density. Moreover, populations of E. japonica are located in a small mosaic area of Kochi Prefecture in accordance with serpentine outcrops.…”

“…E. japonica was analyzed in a total of 60 individuals from the serpentine areas (30 from Ikou and 30 from Kagami) and 93 individuals from the inland areas (30 from Okina, 33 from Shigeto, and 30 from Noichi) (Figure 2). Shiba et al (2021) reported methods of morphological and anatomical analyses in E. japonica. Therefore, we followed these methods in this study.…”

“…It is doubtful whether E. japonica is accompanied by the above-mentioned modifications in the serpentine condition. As for the morphological and anatomical modification of this species to adapt to different environmental conditions, Shiba et al (2021) recently indicated that the leaves of this species along rivers were significantly smaller to adapt to sudden flooding and strong river currents after heavy rain. Moreover, the stomatal density of riverside populations was significantly higher in response to soil moisture, which appears to correspond to riverside conditions (Shiba et al, 2021).…”

“…As for the morphological and anatomical modification of this species to adapt to different environmental conditions, Shiba et al (2021) recently indicated that the leaves of this species along rivers were significantly smaller to adapt to sudden flooding and strong river currents after heavy rain. Moreover, the stomatal density of riverside populations was significantly higher in response to soil moisture, which appears to correspond to riverside conditions (Shiba et al, 2021). This report explored adaptations of E. japonica to other environmental conditions, with morphological and anatomical modifications.…”

Serpentine Adaptation of Ligustrum japonicum Thunb. (Oleaceae) Based on Morphological and Anatomical Approaches

“…In this study, we performed morphological and anatomical analyses of L. japonicum based on Shiba et al (2021). For morphological analysis, the length, width, and thickness of the leaf blade were measured using a digital caliper and micrometer.…”