铀对菠菜叶片光合作用影响的研究

Effects of Uranium on Photosynthesis of Spinach Leaves

为了进一步揭示铀对植物光合作用的影响机理,用不同浓度铀[0、20、50、100、150mg·kg-1]土培处理6叶期菠菜(Spinacia oleracea L.),分别于处理7、14、21、28d后分析铀对菠菜叶片光合色素含量、光合气体交换参数、叶绿素荧光参数和生长指标的影响。结果显示:(1)低浓度铀(20、50mg·kg-1)显著促进菠菜叶片的叶绿素含量和净光合速率(Pn)、气孔导度(Gs)以及蒸腾速率(Tr)等光合气体交换参数;高浓度铀(100、150mg·kg-1)则表现出显著抑制作用,且处理浓度越高,处理时间越长,光合气体交换参数的下降幅度就越大,而胞间CO2浓度(Ci)却反而上升,说明导致Pn下降的主要原因是非气孔因素。(2)高浓度铀处理显著影响菠菜叶片的叶绿素荧光动力学参数,其中光系统Ⅱ(PSⅡ)的最大荧光(Fm)、最大光化学效率(Fv/Fm)和PSⅡ潜在活性(Fv/F0)均显著降低,而初始荧光(F0)显著升高。(3)菠菜幼苗的根长、株高、生物量均随着铀浓度的增加表现出先应激性上升后下降的动态变化。研究表明,低浓度铀可以显著增加菠菜叶绿素含量,有效改善叶片光合效率,促进幼苗的生长发育,而高浓度铀则会抑制菠菜叶片的光合作用,导致光合效率显著下降,显著抑制幼苗的生长发育。

The soil cultivation experiment was used to investigate the effects of uranium on the photosynthetic characteristics of spinach（Spinacia oleracea L.）leaves.Spinach seedlings of the six-leaf stage were treated with different concentrations of uranium [UO2（CH3CO2）2·2H2O]（0,20,50,100,150mg·kg^（-1））,and photosynthetic pigment content,photosynthetic gas exchange parameters,chlorophyll fluorescence parameters of leaves,growth indexes were investigated after 7,14,21 and 28days of uranium treatment,respectively.The results showed that：（1）compared with the control,the chlorophyll content,net photosynthesis（Pn）,stomatal conductance（Gs）,transpiration rate（Tr）were significantly improved by low uranium concentration（20,50mg·kg^（-1））,after that with the increase of uranium concentration all of the parameters significantly decreased,and along with elevated levels of uranium as well as the duration of treatment,all the parameters then decreased significantly compared with the control while intercellular CO2concentration（Ci）was getting rise.It showed that the decline of Pn was caused by nonstomatal factors.（2）High uranium concentration obviously influenced on the chlorophyll fluorescence parameters of plant leaves.PhotosystemⅡ（PSⅡ）maximum fluorescence（Fm）,PSⅡ maximum photochemical efficiency（Fv/Fm）,PSⅡpotential activity（Fv/F0）,declined obviously,while minimum fluorescence（F0）were obviously rise.（3）Root length,plant height and biomass showed a obvious rise under low concentrations of uranium treatments,and a decline under high concentration（100,150mg·kg-1）uranium treatments.Thus,low uranium concentration could improve photosynthetic function of spinach seedlings and increase photosynthetic efficiency,but a high concentration can harm the photosynthetic apparatus and inhibit photosynthetic efficiency.