吉林舒兰地区蒙古栎幼苗光合荧光特征对模拟氮沉降的响应

Response of photosynthetic and fluorescence characteristics of Quercus mongolica seedlings to simulated nitrogen deposition in Shulan,Jilin,China

蒙古栎(Quercus mongolica)是我国东北地区重要的生态树种,为揭示氮沉降加剧背景下东北地区蒙古栎幼苗对氮添加的响应机制,以吉林省舒兰市地区人工造林的蒙古栎幼苗为研究对象,设置空白对照(CK:0 kg hm^(-2)a^(-1)),低氮(LN:50 kg hm^(-2)a^(-1))和高氮(HN:100 kg hm^(-2)a^(-1))3种氮梯度,从光合荧光性状入手揭示蒙古栎幼苗光合生理生态特征随氮添加的变化.结果表明:(1)与对照相比,低氮组蒙古栎幼苗苗高增加了8.68%,地径增加了23.34%.(2)幼苗叶片叶绿素归一化指数和修正红边单比指数均为低氮最高,对照样地最低,且3种处理相互间差异均显著.结构不敏感植被光谱指数施氮下显著高于对照,且低氮与高氮间差异不显著.(3)光合参数中幼苗的最大净光合速率与对照组的12.59μmol m^(-2)s^(-1)相比,低氮组增长为14.47μmol m^(-2)s^(-1),高氮组下降至11.67μmol m^(-2)s^(-1),气孔导度与最大净光合速率呈正相关.(4)叶片磷含量施氮处理较对照显著降低,对照样地氮磷比小于14,低氮和高氮处理大于14,不同氮处理下植株叶片碳、氮、钙含量无显著差异.(5)高氮下实际光化学效率、PSⅡ的非循环光合电子传递速率、光化学淬灭系数与PSⅡ反应中心受体侧质体醌库的大小显著降低,非光化学淬灭系数值提高.本研究表明,蒙古栎幼苗在低氮浓度下叶绿素含量显著上升使得植株光合速率加快,促进植株的生长;高氮环境下受气孔限制、电子传递能力的减弱以及捕获的光能以荧光及热形式耗散增加,使得植株光合及生长受到明显的抑制.本研究揭示了蒙古栎幼苗对不同氮浓度的响应机制,可为我国东北地区人工造林时蒙古栎树种的应用提供参考.

Quercus mongolica is an ecologically important tree species found in Northeast China.This study aimed to reveal the response of Quercus mongolica seedlings to intensified nitrogen(N)deposition,which may provide a reference for forest plantations in Northeast China.Using the planted Quercus mongolica seedlings in Shulan City,Jilin Province,this study investigated the responses of Quercus mongolica seedlings across an N addition gradient,with a focus on the spectral index,photosynthetic characteristics,leaf element contents,and fluorescence characteristics.The N addition gradient included three levels:a blank control(CK;0 kg hm^(-2)a^(-1)),low N addition(LN;50 kg hm^(-2)a^(-1)),and high N addition(HN;100 kg hm^(-2)a^(-1)).This results showed that(1)LN increased seedling height by 8.68%and stem diameter at ground height by 23.34%compared with the control treatment.(2)Among the N addition treatments,LN had the highest chlorophyll normalized index and modified red edge single-ratio index,whereas the lowest values were observed in CK.The structure-insensitive pigment index did not change significantly between LN and HN but was significantly higher than that of CK.(3)The maximum net photosynthesis of seedlings in CK,LN,and HN were 12.59,14.47,and 11.67μmol m^(-2)s^(-1)respectively.Stomatal conductance was positively correlated with maximum net photosynthesis.(4)Leaf phosphorus contents in the N addition treatments were considerably lower than that in CK.N/P was less than 14 in CK but higher than 14 in LN and HN.Varying N addition did not alter leaf carbon,N,or Ca contents.(5)High N addition decreased the actual photochemical efficiency,acyclic photosynthetic electron transfer rate,photochemical quenching coefficient,and size of the acceptor-side plastoquinone pool in the PSII reaction center,but increased the non-photochemical quenching coefficient.Collectively,the results indicated that the CK treatment was limited by N,and the LN and HN treatments were limited by N and P.Low N addition increased the chlorophyll content of Quercus mongolica,which further promoted the photosynthetic rate and seedling growth.Owing to the limitations of stomatal conductance,weak electron transfer efficiency,and increased fluorescence and heat dissipation,high N addition significantly decreased photosynthesis and growth.