增强UV-B辐射和多效唑对绿豆光合作用的影响

使用TPS-1便携式光合仪结合Farquhar和Sharkey的理论测定或计算增强UV-B辐射、多效唑（PP333）及其复合处理幼苗的相关光合指标，并同时测定核酮糖-1，5-二磷酸羧化/加氧酶（Rubisco）含量.发现UV-B辐射降低净光合速率（Pn）、气孔限制值（Ls）和气孔导度（Gs），但使胞间隙CO2浓度（Ci）增加；PP333提高Pn、Gs和Ci，却使Ls下降；与PP333处理相较，UV-B+PP333诱导Pn、Gs和Ci降低，却促进Ls增加；UV-B对Pn、叶肉细胞光合能力（Ao）、表观量子效率（AQY）、羧化效率（dPn/dCi）和Rubisco含量的降低程度大于PP333对上述指标的提高程度，亦大于PP333处理下UV-B对上述指标的抑制程度.结果表明，UV-B降低Pn的主要原因为叶肉细胞光合活性的抑制，而PP333促进Pn及PP333减轻UV-B对Pn的抑制效应主要是通过调节Gs实现的.

The Effects of Increased UV-B Radiation and Paclobutrazo on Photosynthesis in Mung Bean Seedlings

The photosynthetic parameters of mung bean seedling in present of increased UV-B radiation,paclobutrazo (PP_ 333 ) or their combined treatment were determined with TPS-1 photosynthesis system or calculated according to the theory of Farquhar and Sharkey.The content of RuBP carboxylase-oxygenase (Rubisco) was also assayed simultaneously.In the first leaf of seedling,UV-B radiation resulted in decreases in net photosynthetic rate (Pn),stomatal limitation value (Ls) and stomatal conductance (Gs),which were accompanied by increase in intercellular CO_2 concentration (Ci).PP_ 333 elevated Pn,Gs and Ci,and reduced Ls.In comparison with PP_ 333 treatment,UV-B PP_ 333 induced reduction of Pn,Gs and Ci,but promoted Ls to rise.Pn,mesophyl photosynthetic capacity (Ao),apparent quantum yield (AQY),carboxylation velocity of Rubisco (dPn/dCi) and the content of Rubisco were reduced both in UV-B treatment (in comparison to control) and UV-B PP_ 333 treatment (in comparison to PP_ 333 treatment) seedlings, and the reductive extent was greater in UV-B treatment seedling than in UV-B PP_ 333 treatment seedling.And the reductive effects of UV-B radiation on Pn,Ao,AQY,dPn/dCi and Rubisco content were bigger than the promotive effects of PP_ 333 treatment on those parameters.These results prove that UV-B radiation depresses Pn mainly by inhibiting photosynthetic activities of mesophyll cell,while the dominant reasons of PP_ 333 promoting Pn and UV-B radiation inhibiting Pn in UV-B PP_ 333 treatment seedling are the changes of Gs.