施氮水平对羊草叶片光合特性和叶绿素荧光特性的影响

为了探究科尔沁沙地生境下人工羊草(Leymus chiueusis)草地的适宜氮肥水平，分析追施氮肥对羊草叶片叶绿素含量、光合特性和叶绿素荧光特性的影响，本研究采用随机区组设计，于2018年4月20日在人工羊草草地追施0，50，100，150，200 kg·hm^-2不同水平氮肥(纯N)，5月20日测定羊草叶片叶绿素含量、光合和叶绿素荧光参数。结果表明，随着氮素水平的提高，羊草上部叶片(旗叶和倒二叶)和下部叶片(倒三叶)的叶绿素含量、净光合速率(Pn)、气孔导度(Gs)、蒸腾速率(Tr)、最小荧光强度(F₀)、最大荧光(Fm)和PSII的最大光能转换效率(Fv/m)均呈现先增加后降低的趋势，在N₁₅₀处理下最高；而胞间CO₂浓度(Ci)和非光化学猝灭系数随着氮素水平的升高呈现先降低后升高趋势。在科尔沁沙地生境下追施150 kg·hm^-2(纯N)氮肥有利于提高光合作用，降低荧光特性，从而对羊草的生长有促进作用。

Effects of Nitrogen Application Level on Leaf Photosynthetic Characteristics and Chlorophyll Fluorescence Characteristics of Leymus chinensis

In order to explore the appropriate nitrogen fertilizer level for artificial Leymus chiueusis grassland in the Horqin sandy habitat,and analyze the effects of topdressing nitrogen fertilizer on the chlorophyll content,photosynthetic characteristics and chlorophyll fluorescence characteristics of Leymus chinensis leaves,this study adopted a random block design.Applying 0,50,100,150,200 kg·hm-2 nitrogen fertilizer(pure N)on artificial Leymus chinensis grassland on April 20,2018 and measuring Leymus chinensis leaves on May 20 Chlorophyll content,photosynthesis and chlorophyll fluorescence parameters.The results showed that with the increase of nitrogen level,the chlorophyll content,net photosynthetic rate(Pn),stomatal conductance(Gs)and transpiration of the upper leaves(flag leaves and first two leaves)and lower leaves(first three leaves)of Leymus chinensis Rate(Tr),minimum fluorescence intensity(F 0),maximum fluorescence(Fm)and maximum light energy conversion efficiency(Fv/m)of PSII all showed a trend of first increasing and then decreasing,the highest under N150 treatment;while the intercellular CO 2 concentration(Ci)and non-photochemical quenching coefficient(NPQ)showed a trend of first decreasing and then increasing with the increase of nitrogen level.Topdressing 150 kg·hm-2(pure N)nitrogen fertilizer in Horqin sandy habitat is beneficial to improve photosynthesis,reducing fluorescence characteristics,and promoting the growth of Leymus chinensis.