增强UV-B辐射和NaCl复合胁迫下绿豆光合作用的气孔和非气孔限制

研究了0.35 W/m2的UV-B辐射、0.4%NACl及其复合胁迫下绿豆(Phaseolus radiatus L.)幼苗光合作用的气孔和非气孔限制.发现各胁迫处理下,幼苗净光合速率、气孔导度、光合能力、羧化效率和Rubisco含量均明显降低;细胞间隙CO2浓度在各胁迫处理前期低于对照,后期高于对照;气孔限制值除复合处理第5天外,其余均高于对照;复合处理下上述指标的变化程度均大于两胁迫因子单独处理.表明各胁迫下光合速率的降低既有气孔因素也有非气孔因素,但前期以气孔限制为主,后期以非气孔限制为主;Rubisco含量的降低是各胁迫下光合速率降低的非气孔因素.

Stomatal and Nonstomatal Limitations of Photosynthesis in Mung Bean Leaves Under the Combination of Enhanced UV-B Radiation and NaCl Stress

Stomatal and nonstomatal limitationsof photosynthesis in mung bean(Phaseolusradiatus L.) leaves under the combination of0.35W/m2 UV-B radiation and 0.4% NaCl stresswere studied. Separated or combined treatmentsof enhanced UV-B radiation and NaCl stress allresulted in a decrease in net photosynthetic rate,stomatal conductance, photosynthetic ability,efficiency of CO2 carboxylation and Rubiscocontent, and the extent of those decreases en-hanced obviously with the increase of treatmentdays (Figs.1,2A,3,4). Intercellular CO2 concen-tration tended to decrease in short period, fol-lowed by a gradual increase and to be higher thanthe control on the seventh day after treatmentunder NaCl stress alone, while a tendency ofgradual increase was observed under enhancedUV-B radiation alone or two stresses combinedand the concentration was higher than the con-trol after three day of treatments (Fig.2B). Bycontrast, the tendency of stomatal limitationvalue was just reverse to the intercellular CO2concentration, but the stomatal limitation valuewas always higher than control under all stressconditions (did not include that on the fifth dayunder the combined stresses) (Fig.2C). As com-pared with an individual stress the effect of com-bined stress on the above parameters was moreserious (Figs.14). These results indicate that un-der all stress conditions the inhibition of photo-synthesis in mung bean leaves is the results ofboth stomatal and nonstomatal limitations. Andthe stomatal limitation is dominant in shortperiod, nonstomatal limitation becomes thedominant one in longer period. The decrease inRubisco content leads to nonstomatal limitationof photosynthesis under all stresses.