NaCl胁迫对马齿苋光合作用及叶绿素荧光特性的影响

以马齿苋为材料,采用温室盆栽法研究了14 d NaCl胁迫处理对其幼苗生长、光合作用和叶绿素荧光特性的影响.结果显示:(1)马齿苋幼苗的鲜重和株高在25 mmol·L-1 NaCl胁迫时与对照无显著差异,但其随着NaCl浓度的继续增加均显著降低,且其生物量受到的抑制早于株高.(2) NaCl胁迫下,马齿苋幼苗叶片净光合速率(Pn)降低,胞间二氧化碳浓度(C1)增大,且两者的变化幅度随着NaCl浓度增加而增大.(3)NaCl胁迫下,马齿苋幼苗叶片的初始荧光(F0)、最大荧光(Fm)、可变荧光(Fv)、恒态荧光(Fs)、恒态荧光与初始荧光差值(△F0)、PSⅡ潜在光化学效率(Fv/Fo)和PSⅡ最大光化学效率(Fv/Fm)均降低,叶片光化学荧光猝灭系数(qP)也在NaCl胁迫下降低,而非光化学荧光猝灭系数(NPQ)则上升；在0～50 mmol·L-1NaCl胁迫下,幼苗叶片各荧光参数下降幅度小于其他高浓度NaCl胁迫.研究表明,在NaCl胁迫条件下,马齿苋幼苗叶片的光合作用受光抑制伤害,但在低浓度NaCl下能够较多地将光能用于光化学反应,光抑制程度较低,保持了较高的净光合速率,明显减轻盐胁迫对植株生长的影响,表现出一定的耐盐性.

Characteristics of Photosynthesis and Chlorophyll Fluorescence in Portulaca oleracea under NaCl Stress

Pot experiments were carried out to study the effects of NaCl stress on the characteristics of photosynthesis and chlorophyll fluorescence in Portulaca oleracea L.Eight different concentrations of NaCl were applied:0,25,50,75,100,150,200,250 mmol·L-1.The results showed as follows:(1)The plant fresh weights and heights of seedlings had no difference with the control when the concentration of NaCl was 25 mmol·L-1,but decreased with increasing NaCl concentration when the NaCl concentration was above 25 mmol·L-1.When stressed by NaCl,inhibition was the first biomass,then followed by plant height.(2)With increasing NaCl concentration,net photosynthetic rate(Pn) decreased,intracellular CO2(Ci) increased,and the magnitude of changes of Pn and Ci compared with the control increased with increasing NaCl concentration.(3)Minimal fluorescence(F0),maximum fluorescence(Fm),variable fluorescence(Fv),stable fluorescence(Fs),difference between Fs and F0(△F0),PSⅡ potential fluorescence efficiency(Fv/F0),PSⅡmaximum fluorescence efficiency(Fv/Fm) and photochemical quench(qP) of seedlings all decreased when stressed by NaCl,while NPQ increased.And at low NaCl concentrations(0~50 mmol·L-1) stress,the fluorescence parameters decreased less than other high NaCl concentrations.So P.oleracea L.was injured by photo-inhibition under NaCl stress,and at low concentrations,plant applied more light energy to photochemical reaction to maintain a high net photosynthetic rate,the degree of photo-inhibition was lower,therefor,NaCl stress had little effect on growth.