Cd胁迫对两种龙葵光合生理及叶绿素荧光特性的影响

为探究和比较两种不同龙葵对Cd胁迫的光合生理和叶绿素荧光特性响应的差异,试验以Cd超富集植物龙葵(Solanum nigrum)和少花龙葵(Solanum americanum)为材料,于2018年3月采用水培试验,研究了不同浓度(0、20、80、320μmol·L^-1)Cd胁迫对两种龙葵植株形态指标、气体交换参数、叶绿素及叶绿素荧光特性等的影响。结果表明:不同浓度Cd胁迫显著影响两种龙葵生长,两者的Cd耐受存在差异。少花龙葵在Cd浓度≥20μmol·L-1时生长受到抑制(P<0.05);随Cd浓度增加,少花龙葵的形态指标、生物量积累、叶绿素含量、叶片净光合速率(Pn)、气孔导度(Gs)、蒸腾速率(Ts)、PSⅡ最大光化学效率(Fv/Fm)和PSⅡ潜在活性(Fv/Fo)均较CK显著降低(P<0.05),但初始荧光(Fo)、叶绿素a/b有上升趋势;当Cd浓度≥80μmol·L^-1时,少花龙葵PSⅡ的受损程度加重。龙葵则在Cd浓度≥80μmol·L^-1时受到生长抑制,随Cd浓度增加,龙葵相应指标均呈下降趋势(P<0.05),但其形态指标、生物量积累及叶绿素荧光参数等指标的降低范围均小于少花龙葵。此外,Cd胁迫对两种龙葵传能效率的抑制比光能转化效率的抑制更为明显。20μmol·L^-1 Cd胁迫时,两种龙葵光合作用主要受气孔因素限制;80~320μmol·L^-1 Cd胁迫时,其光合作用主要受非气孔因素限制。研究表明,Cd胁迫在少花龙葵的生长和光合方面表现出更显著的抑制作用;受Cd浓度的影响,两种龙葵光合作用的降低是气孔限制和非气孔限制综合作用的结果。研究进一步从光合生理和叶绿素荧光特性响应方面证明龙葵对Cd胁迫的耐受能力强于少花龙葵。

Effects of cadmium stress on photosynthetic physiology and chlorophyll fluorescence in Solanum nigrum and Solanum americanum

To study and compare the effects of cadmium(Cd)stress on plant photosynthetic physiology and chlorophyll,Cd hyperaccumulators of Solanum nigrum and Solanum americanum were selected as materials.A water culture experiment was conducted to observe and analyze their growth and gas exchange parameters,as well as their chlorophyll contents and chlorophyll fluorescence parameters under different Cd levels(0,20,80,and 320μmol·L^-1).The results showed that S.nigrum and S.americanum possessed different Cd tolerance abilities.The growth of S.americanum was inhibited when Cd content≥20μmol·L^-1(P<0.05)as its morphological indicators,biomass,chlorophyll content,net photosynthetic rate(Pn),stomatal conductance(Gs),transpiration rate(Ts),the maximum photochemical efficiency(Fv/Fm),and PSⅡ potential activity(Fv/Fo)were all significantly decreased under increasing Cd stress compared with those of the control.However,the Fo and Chla/Chlb values of S.americanum increased under Cd stress.Cadmium could destroy the chloroplast structure in S.americanum and increase PSⅡ damage at Cd≥80μmol·L^-1.S.nigrum growth was inhibited when Cd content was>80μmol·L^-1,and all S.nigrum indices decreased with increasing Cd stress(P<0.05)but with smaller reductions than those observed for S.americanum indices.Furthermore,Cd stress inhibited energy transfer efficiency to a greater extent than light energy conversion efficiency.In addition,photosynthesis was mainly influenced by stomatal factors when Cd stress was 20μmol·L^-1,whereas it was affected by non-stomatal factors when Cd stress was 80~320μmol·L^-1.In summary,Cd stress showed more obvious inhibitory effects on the growth and photosynthesis of S.americanum than on those of S.nigrum.The reductions in photosynthesis observed in the two species were the result of the combined effects of stomatal factors and non-stomatal factors.The present study further demonstrated that Cd tolerance was stronger in S.nigrum than in S.americanum in terms of photosynthetic physiology and chlorophyll fluorescence characteristics.