Effects Of Nitrogen Application On Growth And Photosynthesis Of Zizania Latifolia

An experiment was conducted to investigate the effects of nitrogen application (10,30 and 60 kg/667 m2) on plant growth and photosynthesis of Zizania latifolia, an aquatic vegetable. In this experiment, nitrogen fertilization showed little effects on plant height and leaf width. However, leaf number and leaf length were significantly increased, and increase in leaf thickness was also observed after nitrogen application. Nitrogen also promoted tillering. The application of 30 kg/667 m2 of nitrogen showed significant impact on growth, while little or no nitrogen applied will result in a reduction in growth and tillering. However, excessive growth of stems and leaves, the reduced number of tillers were founded when nitrogen applied at the rate of 60 kg/667m2.Chlorophylls (a+b) contents in the leaves were increased in the application of 30 kg/667m2 of nitrogen. Nitrogen was found to improve photosynthesis and net photosynthetic rate (Pn) of leaves, which may result from decreased Ci and increased Gs and Tr. Pn showed greatest enhancement when the nitrogen applied at the rate of 30 kg/667m2 compared to that of 10 and 60 kg/667 m2.Maximum photochemical efficiency of PSⅡ(Fv/Fm), quantum yield of PS II electron transport (ΦPSⅡ) and Apparent photosynthetic electron transfer rate (ETR) in the leaves increased significantly after application of 30 kg/667m2 of nitrogen compared to other treatments. Photocheimcal quenching coefficient (qP) increased and non-photocheimcal quenching coefficient (qN) decreased after application of nitrogen, especially in treatment of 30 kg/667 m2.In this experiment, application of 30 kg/667 m2 of nitrogen increased economic yield, while 60 kg/667 m2 of nitrogen enhanced growth but had little impact on economic yield. And nitrogen applied at the rate of 10 kg/667m2 resultd in lower biological yield and economic yield.