五节芒不同种群对Cd污染胁迫的光合生理响应

Photosynthetic physiological response of two Miscanthus floridulus populations to Cd stress

通过盆栽模拟试验,以分别来自粤北大宝山矿区和惠州博罗非矿区的两个五节芒种群为试验材料,比较研究了两个种群在Cd胁迫下的气体交换参数、叶绿素荧光特性、光合色素含量和叶绿体超微结构变化的差异。结果表明:(1)Cd胁迫下五节芒两种群叶片净光合速率(Pn)、蒸腾速率(E)、气孔导度(Gs)、胞间二氧化碳浓度(Ci)、叶绿素含量(Chl)都有不同幅度的下降;叶绿体超微结构遭到破坏。矿区种群随Cd胁迫程度的加深,净光合速率下降较慢,叶绿体的外形及基粒结构受到的影响较小。(2)轻度Cd胁迫下气孔限制是五节芒非矿区种群Pn降低的主要因素,中度和重度Cd胁迫下非气孔限制是Pn降低的主要因素。(3)Cd胁迫下五节芒两种群PSⅡ反应中心最大光化学效率(Fv/Fm)、PSⅡ潜在活性(Fv/Fo)、PSⅡ有效光化学效率Fv′/Fm′均有所下降。总体上矿区种群降幅较小,PSⅡ利用光能的能力及PSⅡ的潜在活性均较强。PSⅡ光化学猝灭系数(qP)、非光化学猝灭系数(NPQ)的变化表现为Cd胁迫下两种群qP值降低、NPQ值升高,总体上抗性强的矿区种群qP降低的幅度低且NPQ升高幅度大。随着Cd胁迫浓度增加,矿区种群实际光化学反应效率(ΦPSⅡ)和电子传递速率(ETR)变化幅度不大,而非矿区种群显著下降,表明矿区种群PSⅡ反应中心电子传递活性受到的影响小,光合机构的损伤程度低。研究表明,五节芒矿区种群对重金属Cd有较强的耐受能力,适合作为金属矿区植被恢复建设的禾本科先锋物种。

The gas exchange,chlorophyll fluorescence parameter,Chlorophyll（chl）contents and chloroplast ultrastructure of two Miscanthus floridulus populations,one population from Boluo an uncontaminated site,and another population from Dabaoshan a mine site,were studied under pot-cultivation experiments treated with heavy metal Cd in green house.The results showed that,（1）Under Cd stresses,the net photosynthetic rate（Pn）,transpiration rate（Tr）,stomatal conductance and chlorophyll content decreased at different extents,and chloroplast ultrastructure was damaged in the leaves of both populations.Compared to the non-mine population,the net photosynthetic rate of the mine population decreased more slowly,and chloroplast shape and grana structure were less affected.（2）Stomatal restriction was the main factor for the Pn＇s decrease in the leaves of the non-mine population under light Cd stress,while the non-stomatal restriction was the main factor for Pn＇s decrease in the leaves of the non-mine population under middle and high Cd stresses.（3）Measurement of fluorescence of PSⅡReaction Center indicated Fv/Fm,Fv＇/Fm＇ and Fv/Fo to decrease in the both populations under Cd stress.However,Fv/Fm and Fv/Fo showed a smaller decrease,but the capability to utilize light and the potential to activate PSⅡ of the mine population remained higher than that of the non-mine population.Quenching（qP）of chlorophyll fluorescence decreased and Non-photochemical Quenching（NPQ）of chlorophyll fluorescence increased for the both populations under Cd stress.Generally,qP decreased less and NPQ increased more for the mine population than that for the non-mine population.Electronic transfer rate（ETR）and PSⅡactual fluorescence efficiency（ΦPSⅡ）of the mine population changed slightly under Cd stress.These results indicated that when under Cd stress,the electron transport activity and photosynthetic apparatus were damaged less in the mine population with high resistance than in the non-mine population with low resistance.Therefore,the Miscanthus floridulus populations from Dabaoshan could be a pioneer species for restoration and rehabilitation of vegetation in a mining area.