Evaluation of shade tolerance of Carex species available for garden-environment planting

The grass species, Carex nemostachys, C. chungii, C. brunnea and C. tristachya, were selected to investigate their shade-tolerance, with Reineckia carnea as control.Their morphological and physiological characteristics, i.e. lengths and widths of leaves, chlorophyll content (Chl a+b), the chlorophyll a/b ratio (Chl a/b), photosynthetic light-response curves and chlorophyll fluorescence, were investigated. There were no significant differences in leaf width when the degree of shade ranged from 0 to 90%; leaf length, Chl a+b, Fv/Fm,Fv/F0 and Fv′/Fm′ increased; but Chl a/b, the light compensation point (LCP) and qN decreased. The maximum Chl a+b occurred in C. chungii and C. tristachya under 75% shade, while the minimum Chl a/b occurred in C.chungii and C. tristachya under 75% and 50% shade, respectively. The maximum light saturation point (LSP) of C. brunnea, C. chungii and C. tristachya occurred under 50% shade, while that of C. nemostachys appeared without any shade. Under 75% shade, R. carnea had the highest LSP. Results indicated that among the five plant species, C. brunnea was the most shade-tolerant, followed by R. carnea, C. nemostachys, C. tristachya and C. chungii. Among these species, C. brunnea and C. nemostachys are better adapted to changes in light intensity than the other three species. Therefore, C. nemostachys should be selected as greening and beautifying species for both stagnant water areas and areas with changing water levels (i.e. reservoirs and rivers). C. brunnea could be used as a greening species under strong shade, such as undergrowth, the north side of buildings and open spaces under bridges. The other two species, C. tristachya and C. chungii are recommended for planting at the margin of evergreen broad-leaved forests, as roadside grasses and with hillside shrubs, due to their weak shade-tolerance.