Effects Of Cesium On Photosynthesis And The Physiological Parameters Of Stress Resistance In Spinach And Populus

Spinach and Populus were chosed as materials to explore response mechanism induced by cesium and provide theoretical and technical support for the phytoremediation to Cs pollution. Spinach was raised in quartz salad and Hoagland solution culture system which was treated with Cs(0、84、168、926、1683、3367 mg/kg), Populus was raised in the soil treated with Cs(0、20、50、100、200、400 mg/kg). The uptake and distribution of strontium in Spinach and its effects on the growth, resilience indicators and photosynthesis were investigated after 3, 6, 9, 12 and 15 days of Cs treatment while the Populus were treated after30, 60 and 90 days. The main results are as follows:(1) The contents of Cs in the and underground s of the two plants increased as long as increasing the concentration of Cs. Compared with the aboveground part of Spinach, the contents of Cs in the underground part is higher. The transfer coefficients decreased at high concentration of Cs. The contents of Cs in the parts of Populus is stem > leaf > root.The transfer coefficients stayed at a high level.(2) Low concentrations of Cs promoted the growth and biomass accumulation of plants, and high concentrations of Cs inhibited the growth of plants, which was accompanied by the plants dwarf, yellow leaves, and biomass decrease and the growth inhibition. The most significant promotion appeared at the concentrations of Cs is 926 mg/kg to Spinach,while 100 mg/kg to Populus.(3) The results of Cs stress on resistant physiological indices showed that the activity of CAT,POT, SOD in Spinach dropped after rised while stayed at a high level after the treatment with 400 mg/kg Cs. Due to the serious harmful effects of Cs to membrane, the contents of MDA and Pro in two plants positively correlated with the concentration of Cs. Cs stress has caused salt damage to Populus leaf while the concentration of Cs reached50-400 mg/kg, which would drop the leaf water potential of Populus, rendered water shortage status.(4) The results of Cs stress on photosynthesis of plants showed that the chlorophyll content decreased at high concentrations of Cs and increased at low concentrations. As along as the concentrations of Cs increasing, especially higher than 1683 mg/kg to Spinach and200 mg/kg to Populus, the Pn, Gs, Ci and Tr decreased significantly. The analysis of chlorophyll fluorescence parameters showed that the activity of PSII reaction centers were damaged under high concentrations of Cs.(5) The analysis of the electron transfer activity of thylakoid membranes showed the inhibition of electron transfer activity of PSII by high Cs concentrations. The absorbance spectra and 77 k low fluorescence spectra revealed that Cs could damage the structure and function of thylakoid membranes, and cause the inhibition of the light energy absorption,transmission and distribution, and even lead to the degradation of pigment protein complexes of thylakoid membranes.