[Stomatal and nonstomatal limitations of photosynthesis in mung bean leaves under the combination of enhanced UV-B radiation and NaCl stress].
Stomatal and nonstomatal limitations of photosynthesis in mung bean (Phaseolus radiatus L.) leaves under the combination of 0.35 W/m(2) UV-B radiation and 0.4% NaCl stress were studied. Separated or combined treatments of enhanced UV-B radiation and NaCl stress all resulted in a decrease in net photosynthetic rate, stomatal conductance, photosynthetic ability, efficiency of CO(2) carboxylation and Rubisco content, and the extent of those decreases enhanced obviously with the increase of treatment days. Intercellular CO(2)concentration tended to decrease in short period, followed by a gradual increase and to be higher than the control on the seventh day after treatment under NaCl stress alone, while a tendency of gradual increase was observed under enhanced UV-B radiation alone or two stresses combined and the concentration was higher than the control after three day of treatments. By contrast, the tendency of stomatal limitation value was just reverse to the intercellular CO(2) concentration, but the stomatal limitation value was always higher than control under all stress conditions (did not include that on the fifth day under the combined stresses). As compared with an individual stress the effect of combined stress on the above parameters was more serious. These results indicate that under all stress conditions the inhibition of photosynthesis in mung bean leaves is the results of both stomatal and nonstomatal limitations. And the stomatal limitation is dominant in short period, nonstomatal limitation becomes the dominant one in longer period. The decrease in Rubisco content leads to nonstomatal limitation of photosynthesis under all stresses.
He
Jun-Min
JM
Center of Bioinformation, School of Life Sciences and Technology, Xi'an Jiaotong University, Xi'an 710049, China. hejunming@hotmail.com
She
Xiao-Ping
XP
Liu
Cheng
C
Zhao
Wen-Ming
WM
D027805:Phaseolus / Q000187:drug effects / Q000378:metabolism* / Q000528:radiation effects; D010788:Photosynthesis; D018515:Plant Leaves / Q000378:metabolism*; D012273:Ribulose-Bisphosphate Carboxylase / Q000032:analysis; D012965:Sodium Chloride / Q000494:pharmacology*; D014466:Ultraviolet Rays
D012965:Sodium Chloride; D012273:Ribulose-Bisphosphate Carboxylase