Effects Of Nitrogen Forms On The Physiological Characteristics Of Tea Plant And Tea Leaf Quality

In this paper, a field experiment with three -year-old clonal cultivars of Camellia sinensis (L.) cv.Wuniuzao was carried out in tea plantation in subtropical hilly yellow brown soil.Effects of different nitrogen forms on the activities of glutamine synthetase (GS), glutamate: 2-oxoglutarate aminotransferase (GOGAT), the contents of endogenous hormones: indoleacetic acid(IAA ), abscisic acid (ABA), gibberellin (GA3), zeatin riboside (ZR) and endogenous polyamines in tea leaves, phyotosynthetic characteristics of tea plant and quality of tea were conducted. The results were as belows:The activity of GS and GOGAT was low when fertilizing NO3--N. However, fertilizing NH4+-N could significantly increase the activities of GS and GOGAT. This indicated NH4+-N form could enhance the efficiency of nitrogen assimilation, then promote the growth of tea plants, and lay a foundation for creating a good quality of tea.In NH4+-N trement, the contents of chlorophyll a, chlorophyll b, total chlorophyll and carotenoids were higher than those of other treatments, in particular, the total chlorophyll content was respectively 7.69% higher than in CK, 5.95% higher than in NO3--N trement and 6.98% higher than in NH4+-N + NO3--N trement. The changes of intercellular CO2 concentration (Ci) was consistent with the changes of net photosynthesis rate (Pn). Which indicated that the different nitrogen forms influenced photosynthesis of tea plant by stomatal conductance (Gs). In NH4+-N treatment, the net photosynthesis rate (Pn), stomatal conductance (Gs), intercellular CO2 concentration (Ci), electron transport rate (ETR), photochemical quenching coefficient (qP) and actual photochemical efficiency of PSⅡ(ФPSⅡ) was significantly higher than those of other treatments. High qP values help to improvement the quantum yield of PS, and ultimately help to provide more reducing power for carbon assimilation, then promoting carbon and nitrogen metabolism. These results suggested that fertilizing NH4+-N is more conducive to the photosynthesis.When NH4+-N as nitrogen resource, in spring, summer and autumn the ratio of GA3 / ABA, IAA/ABA in tea plants were all the highest, and at the same time the activities of GS, GOGAT were the highest. From these phenomena it may conclude that nitrogen forms by changing content of endogenous hormones and hormone balance induced changes of enzyme activity, and changes of enzyme activity regulated the expression of metabolic enzyme genes, while metabolic enzyme genes expressing resulted in changes of enzyme activity in vivo, thereby regulating their growth and development.For spring tea, the content of quality composition in NH4+-N, NH4+-N+NO3--N treatments was superior to NO3--N treatments; For summer tea, the content of quality composition in three fertilizing nitrogen treatments were all higher than the control, but the content of quality composition in summer tea were significantly lower than in spring tea in three fertilizing nitrogen treatments; For the content of quality composition in autumn tea, NH4+-N + NO3--N treatments was superior to NH4+-N treatments. The content of quality composition in NO3--N treatments was the lowest. Effects of nitrogen forms on the content of quality composition in different seasons may be associated with the growth and development of tea plants as well as light, heat, water and other external environment conditions. In spring tea, the content of amino acid was the highest, the content of polyphenols was the lowest. In autumn tea, the content of polyphenols was the highest, the content of amino acid was the lowest.