Effects of excessive calcium fertilization on photosynthetic characteristics and chloroplast ultra-structure of tea tree

Tea tree absorbs less calcium than other plants in the same soil usually. In order to probe the effects of excessive calcium fertilization on the photosynthetic physiology of tea leaves and provide the theoretical foundation to explain why the poor growth of tea tree in the soil with high calcium content, this study focused on the changes of chlorophyll content, the leaf photosynthesis, chlorophyll fluorescence parameters and chloroplast ultra-structure of tea leaves treated with excessive calcium using sand culture. The results indicate that the net photosynthetic rate and stomatal conductance of tea leaves are reduced with the increase of calcium concentration, and the leaf chlorophyll content, the primary photochemical efficiency (Fv/Fm), photosynthetic electron transport rate (ETR) and quantum yield of PSⅡ(ΦPSⅡ) are decreased as well, while the ratio of Chl a and Chl b and the minimum fluorescence (Fo) are increased with the increase of calcium concentration. Under the condition of excessive calcium fertilization, the chloroplast structure is destroyed. Meanwhile the growth of tea is restrained. The burl interval, the length of treetop, the amount of leaves and leaf area are lower than those of the control (CK). On the basis of above results, it is concluded that excessive calcium fertilization could damage the membrane of photosystem, and then block the electron photosynthetic rate and decrease light use efficiency of tea leaves, and finally slow down the growth rate of tea shoots.