中文摘要：

采用营养液栽培方式,以＇细叶苦苣＇为实验材料,研究了5个不同供氮水平处理对苦苣干物质积累、光合气体交换参数和叶绿素荧光参数的影响。研究结果表明：5个不同处理的苦苣植株地上和地下部干物质积累量和叶片的叶绿素相对含量（SPAD值）、净光合速率（Pn）、气孔导度（Gs）、蒸腾速率（E）、PSII最大光化学效率（Fv/Fm）以及PSII实际光化学效率（ΦPSII）均随着供氮水平的提高呈现出先升高后降低的趋势,而胞间CO2浓度（Ci）表现出先降低后升高的趋势;不同处理中,供氮水平（8和11 mmol/L）通过提高苦苣叶片光合色素含量、CO2传导能力和PSII光化学反应活性,从而提高了Pn,有效促进了干物质积累。而过低（2 mmol/L）和过高（14 mmol/L）供氮水平不同程度地降低了光合色素含量,抑制了光化学反应活性、从而降低了苦苣叶片光合作用和干物质积累。

英文摘要：

A hydroponic experiment was conducted to investigate the effects of five different nitrogen levels on the dry weight of shoots and roots, photosynthetic gas exchange, and chlorophyll fluorescence parameters in leaves of endive（Cichorium endivia L. cv. Xiyekuju）. The results showed that, with the increasing of application, the dry weight of shoots and roots, chlorophyll relative content（SPAD value）, net photosynthetic rate（Pn）, stomatal conductance（Gs）, and transpiration rate（E）, actual photochemical efficiency of PSII（ΦPSII）, the maximum quantum yield of PSII（Fv/Fm） in leaves of endive under five different nitrogen treatments showed the trend of first increased and then decreased, but intercellular CO2concentration（Ci） values showed the trend of first decreased and then increased. The dry matter accumulation and Pn of endive plants under 8 mmol/L（N8） and 11 mmol/L（N11） nitrogen level treatments were the best among of five different nitrogen treatments, which was related to the higher SPAD value, CO2 transmission capacity, as well as photochemical activity of PS Ⅱ in leaves of endive.Furthermore, the application of low nitrogen（2 mmol/L） or high nitrogen level（14 mmol/L） decreased Pn and inhibited the dry matter accumulation of shoots and roots of endive plants in different degree which was likely due to the decrease the photosynthetic pigment content, CO2 transmission capacity and photochemical activity of PSⅡ in leaves of endive.