不同施氮水平对柳枝稷光合特性及抗旱性的影响

Effects of different nitrogen levels on photosynthetic characteristics and drought resistance of switchgrass (Panicum virgatum)

为了探究宁夏银北盐碱地区柳枝稷高产优质高效栽培过程中最佳的施氮量及其对柳枝稷叶片光合特性及抗旱性的影响,本研究采用大田试验,以Cave-in-Rock品种柳枝稷为供试材料,设无氮添加(0 kg·hm-2,N0)、施低氮(60 kg·hm-2,N60)、中氮(120 kg·hm-2,N120)和高氮(240 kg·hm-2,N240)共4个施氮水平,分析比较了各生育时期内柳枝稷叶片光合特性、渗透调节物质及抗氧化酶活性的变化,同时采用隶属函数法综合评价了盐碱地柳枝稷的抗旱性。结果表明,随着不同施氮水平的增加,柳枝稷各生育时期内叶片叶绿素相对含量(SPAD)、净光合速率(Pn)、气孔导度(Gs)和细胞间隙CO2浓度(Ci)整体呈现先升后降的趋势,均在施中氮(N120)处理下达到峰值。与无氮添加(N0)处理相比,施低氮(N60)、中氮(N120)和高氮(N240)处理下柳枝稷叶片的SPAD值平均增加了4.73%、18.71%和8.86%,净光合速率(Pn)平均提高了5.55%、17.02%和12.41%,气孔导度(Gs)平均升高了7.87%、56.18%和39.33%,细胞间隙CO2浓度(Ci)平均增加了7.86%、30.71%和13.81%。柳枝稷叶片蒸腾速率(Tr)在高氮(N240)处理下达到最大值,叶片水分利用效率(WUE)随着不同施氮水平的增加而逐渐下降。隶属函数分析结果表明,施中氮(N120)处理下柳枝稷各抗旱指标隶属函数值的均值最大。因此,本试验条件下有利于提高柳枝稷叶片光合能力和抗旱性的适宜施氮水平为120 kg·hm-2。

This aim of this study was to determine the optimal nitrogen application rate for high-efficiency cultivation of switchgrass(Panicum virgatum)with good yields and quality in saline-alkali soil in Yinbei,Ningxia.Switchgrass was grown with different levels of nitrogen and its photosynthetic characteristics and drought resistance were analyzed.The P.virgatum cultivar‘Cave-in-Rock’was used as the experimental material,and four levels of nitrogen were applied in the field experiment,as follows:no added nitrogen(0 kg·ha-1,N0),low nitrogen(60 kg·ha-1,N60),medium nitrogen(120 kg·ha-1,N120)and high nitrogen(240 kg·ha-1,N240).The photosynthetic characteristics,contents of osmotic compounds,and activities of antioxidant enzymes in leaves of switchgrass at different growth stages were determined,and the drought resistance of switchgrass was evaluated by the multivariate membership function method.The results showed that with increase in nitrogen application levels,the relative chlorophyll content(SPAD value),net photosynthetic rate(Pn),stomatal conductance(Gs),and intercellular CO2 concentration(Ci)in switchgrass initially increased and then decreased,with peak values in the medium nitrogen(N120)treatment.Compared with the leaves of plants in the N0 treatment,those in the N60,N120,and N240 treatments showed increases of 4.73%,18.71%,and 8.86%,respectively,in the SPAD value;increases of 5.55%,17.02%,and 12.41%,respectively,in the Pnvalue;increases of 7.87%,56.18%,and 39.33%,respectively,in Gs;and increases of 7.86%,30.71%,and 13.81%,respectively,in Ci.The maximum transpiration rate was in the N240 treatment,and the leaf water-use efficiency gradually decreased with increasing nitrogen application levels.The results of the membership function analysis showed that the maximum average value of drought resistance indexes was in the N120 treatment.Therefore,application of nitrogen at an appropriate level(120 kg·ha-1)can improve the photosynthesis and drought resistance of switchgrass growing in saline-alkali soil.