In order to explore suitable nutrient concentration for the growth of Cryptotaenia japonica seedlings, the effects of six different concentrations of Yamasaki nutrient solution (1/12s, 1/10 s, 1/8s, 1/4s, 1/2s and full strength) on the growth, antioxidase activities and chlorophyll fluorescence parameters of Cryptotaenia japonica seedlings were investigated. The results show that the highest Cryptotaenia japonica seedlings' growth factors (plant height, leaf area, stem diameter, fresh and dry weights of shoots, fresh and dry weights of roost, fresh and dry weights of plants) are observed in the 1/8s Yamasaki nutrient solution. The seedling indexes are increased firstly and then declined with the increase of the nutrient solution concentration, and the maximal values of the seeding indexes are observed in the 1/8s nutrient solution, which are significantly higher than those of the other concentrations. When the concentrations of nutrient solution are between 1/12s~1/8s, the activities of POD, CAT and SOD are increased gradually with the increase of the nutrient concentration, while the MDA content is gradually decreased. However, the trends of the POD, CAT and SOD activities and as well as MDA content are contrary under the 1/8s~s nutrient concentrations. When the concentration of the nutrient solution is close to 1/8s, the activities of POD, CAT and SOD are highest, while the MDA content was the lowest. The contents of chlorophyll a, chlorophyll b and total chlorophyll are increased under the lower nutrient concentrations and decreased under the higher concentrations, and the physiological parameters are highest under the 1/8s nutrient solution. Under the 1/4s~full strength Yamasaki nutrient solution, the initial fluorescence (Fo) values are higher than those under the 1/12s～1/10s, while the maximal fluorescence (Fm), potential activity of PSII (Fv/Fo), and the maximal photochemical efficiency of PSII (Fv/Fm) are lower than those under the 1/12s~1/10s. The Fo value is lowest under the 1/8s nutrient concentration, while the values of Fm, Fv/Fo, Fv/Fm are the highest. Our findings suggest that the nutrient concentration plays dual roles on Cryptotaenia japonica seedlings, i.e. at the lower nutrient concentrations, seedling growths are accelerated with the increase of the concentrations due to alleviated nutrient stress, while seedling growths are inhibited the increase of the concentrations under the higher nutrient concentrations due to enhanced nutrient stress. The 1/8 strength Yamasaki nutrient solution is the optimal concentration for growth of Cryptotaenia japonica seedlings.
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