Solute patterns and diurnal variation of photosynthesis and chlorophyll fluorescence in Korean coastal sand dune plants

Four plant species, Elymus mollis Trin., Carex kobomugi Ohwi, Glehnia littoralis F. Schmidt ex Miq., and Vitex rotundifolia L.f., are dominant perennial species in coastal sand dunes of Korea. We examined a physiological adaptation of these species by measurements of diurnal variation in photosynthesis and chlorophyll (Chl) fluorescence and solute patterns in leaves during one season (June), which is favorable for plant growth of all four species. All four species adopted different strategies in order to utilize radiation and to maintain water status under a fluctuating microclimate. Although the lowest water contents among four plant species was found, E. mollis with a high Chl and K⁺ content showed better photosynthetic performance, with high stomatal conductance (g_s), net photosynthetic rate (P_N), instantaneous carboxylation efficiency (CE), and water-use efficiency. Midday depression of P_N in E. mollis and G. littoralis, without a reduction of gs, was associated with a reduction in CE and maximum photochemical efficiency of PSII, indicating nonstomatal limitation. Photosynthesis depression in both C. kobomugi and V. rotundifolia, with relatively low g_s values, could be attributed to both stomatal and nonstomatal limitations. The high storage capacity for inorganic ions in E. molli, C. kobomugi, and G. littoralis may play an efficient role in regulating photosynthesis and maintaining leaf water status through stomatal control, and can also play an important role in osmotic adjustment.