氮素对分蘖期干旱及复水柳枝稷光合生理特性的影响

Effects of Drought stress and Subsequent Rewatering on Leaf Photosynthetic Physioecological Characteristics at Tillering Stage in Switchgrass with Different Nitrogen Management

为揭示引种禾草柳枝稷(Panicum virgatum L.)光合生理对短期干旱的敏感性与旱后恢复能力及施氮效应,采用盆栽控水试验,设置高水[HW,80%FC(田间持水量)],中水(MW,60%FC)和低水(LW,40%FC)3个水分水平,及两个氮肥处理(不施氮和0.1g N/Kg干土),研究了分蘖期柳枝稷叶片光合气孔交换参数和叶绿素荧光参数在土壤逐渐干旱及复水后的变化特点。结果表明:与高水相比,中水和低水下柳枝稷叶片相对含水量(RWC)、叶绿素含量、净光合速率(Pn)、气孔导度(Gs)、蒸腾速率(Tr)、最大光化学效率(Fv/Fm)均显著降低;随自然干旱时间延长,Pn、Gs、Tr、Fv/Fm和光化学淬灭系数(qP)值均呈下降趋势,且施氮处理的降幅较大,以低水施氮降低幅度最大,Pn下降由气孔限制转变为非气孔限制;非光化学淬灭系数(NPQ)值则呈相反的变化趋势;复水后,柳枝稷各光合生理指标均能恢复到水分降低前水平,施氮处理的恢复速度大于不施氮处理。上述表明,柳枝稷具有较强适应低水分条件的能力,一定土壤水分条件下施氮有利于提高其光合能力及复水后的恢复能力;在土壤水分低于40%FC施氮则加重柳枝稷受胁迫程度,降低柳枝稷光合性能。

The objective of the study were to evaluated the effect of short-term drought stress and subsequent rewatering on leaf photosynthetic physioecological characteristics of introduced herbaceous species switchgrass(Panicum virgatum L.)at tillering stage under different nitrogen treatments.A pot experiment was conducted with two nitrogen treatments(non-N and 0.1 g N/Kg dry soil)and three soil water regimes of high water(HW,80% of field capacity,FC),medium water(MW,60% FC)and low water(LW,40% FC).The changes of gas exchange parameters and chlorophyll fluorescence of switchgrass during drought and rewatering at the tillering stage were investigated.Results showed that leaf relative water content(RWC),chlorophyll content,net photosynthetic rate(Pn),stomatal conductance(Gs),transpiration rate(Tr)and maximum photochemical efficiency(Fv/Fm)of switch grass under 60% FC and 40% FC treatment were all significantly reduced compared with 80%FC.With the extension of natural drought stress time,the value of Pn,Gs,Tr,Fv/Fm,photochemical quenching coefficient(qP)showed a downward trends.Moreover,the reduction rate of nitrogen fertilizer treatment was relative large than non-N treatment,and the reduction range of LW(40%FC)with N treatment was the largest.During the process of soil drying,the decrease of Pnfor switchgrass changed from stomatal limitation to non-stomatal limitation.The value of non-photochemical quenching coefficient(NPQ)showed an opposite trend.After rewatering,all the parameters recovered and approached to the level before soil water decreased at the end of the experiment,and the recovery rate of nitrogen treatment was higher than that of non-N treatment.All these indicated that switchgrass had a strong adaptability to low soil water condition.Nitrogen application can improve photosynthetic and recovery ability after rewatering of switchgrass leaves under certain soil water conditions;When the soil moisture was less than 40% FC,nitrogen application will aggravate the stress of switchgrass and reduce the photosynthetic performance.