【摘要】 研究和比较了等渗(-0.53MPa)的PEG-6000、NaCl、钠盐(无Cl-)和氯化物(无Na+)溶液处理6d对栽培大豆品种‘Lee68’(耐盐性较强)和‘N23674’(耐盐性较弱)幼苗光合作用的离子效应。结果表明:PEG-6000处理使两品种叶片叶绿素含量和Rubisco活性较对照低,但降幅不如同样渗透压的NaCl、钠盐(无Cl-)和氯化物(无Na+)溶液明显。PSII最大光化学效率(Fv/Fm)、电子传递速率(ETR)和PSII光化学的有效量子产额(Fv’/Fm’)在PEG-6000处理2d和6d时显著下降,但在3种等渗盐处理下,多显著下降。两品种叶片气孔导度(Gs)和净光合速率(Pn)在4种胁迫处理下均显著下降,其中在3种盐处理下更明显,但胞间CO2浓度(Ci)仅在PEG-6000处理时下降,在盐处理下反而升高。两品种叶片叶绿素含量、Rubisco活性、Fv/Fm、ETR、Fv’/Fm’、Pn、Gs等在氯化物(无Na+)溶液处理的下降幅度和叶绿体中Cl-含量及其与Na+总量的增加幅度均大于钠盐(无Cl-)处理的,在耐盐性弱的‘N23674’品种中更明显。可见,在NaCl胁迫对栽培大豆幼苗光合作用的毒害效应中,渗透胁迫较轻,离子毒害较重,其中Cl-的毒害大于Na+的。更多还原

【Abstract】 Ion-specific stress effects of Na+ and Cl- on photosynthesis of seedlings of two soybean (Glycine max) cultivars (the salt-tolerant ‘Lee68’ and the salt-sensi- tive ‘N23674’) were studied and compared under isoosmotic (–0.53 MPa) solutions PEG-6000, NaCl, Na+ (without Cl–) and Cl– (without Na+)for 6 d. The results showed that the chlorophyll contents and the ribulose bisphosphate carboxylase/oxygenase (Rubisco) activities of seedlings of both cultivars were inhibited to a less degree by PEG-6000 than by NaCl, Na+ (without Cl–) or Cl– (without Na+) solutions. The maximum photochemi- cal efficiency of photosystem II (PSII) (Fv/Fm), electron transfer rate (ETR) and effective quantum yield of PSII photochemistry (Fv’/Fm’) were lowered significantly by PEG-6000 treatment for 2 d and 6 d. But when treated with the three isoosmotic salt stresses, most of the above three indexes significantly declined. Leaf stomatal con- ductance (Gs) and net photosynthetic rate (Pn) in both cultivars were significantly decreased under the four isoosmotic treatments, and much more drops were ob- served in the three salt stresses, but the intercellular CO2 concentration (Ci) decreased by PEG-6000 treatment and increased by the three salt stresses. Higher decreases in- cluding chlorophyll content, Rubisco activity, Fv/Fm, ETR, Fv’/Fm’, Pn and Gs, and higher contents of Cl– as well as the content of Cl– plus Na+ in chloroplasts were all observed under Cl– (without Na+) treatment than those under Na+ (without Cl–) treatment, especially for the salt- sensitive cultivar ‘N23674’. The results indicate that, among the adverse effects of NaCl stress on photosyn- thesis of G. max seedlings, the ionic toxicity was stron- ger than osmotic stress, and the toxicity of Cl– was more severe than that of Na+.更多还原