Effects of Exogenous Cadmium and Temperature Change on Photosynthetic Characteristics of Different Varieties of Rice at Heading Stage
The effects of exogenous cadmium(Cd)and temperature change on photosynthetic characteristics of rice plants were studied in order to provide a theoretical basis for the coping with the combination of soil Cd pollution in rice field and the climate warming during rice growth.Photosynthetic parameters,fluorescence parameters and biomass of different rice cultivars(Wuyungeng 30 and Xinliangyou 6)at heading stage were determined and the fluorescence kinetic curves of rice were analyzed under the condition of adding exogenous Cd(0 and 2 mg/kg soil)and artificially simulating temperature(daytime/nighttime 30 ℃/25 ℃,CK;33 ℃/28 ℃,T1;36 ℃/31 ℃,T2).The results showed single Cd treatment had signifiicant effect on SPAD values of Xinliangyou 6,while single warming treatment significantly reduced SPAD value of Wuyungeng 30.Although the combined effects of Cd and temperature didn't significantly affect the net photosynthetic rate(Pn)of Wuyungeng 30 and Xinliangyou 6,single Cd treatment significantly reduced Pn of the two rice cultivars and single warming treatment significantly affected Pn of Xinliangyou 6.The shape of chlorophyll fluorescence induction kinetics(O-J-I-P)was affected by Cd and warming treatment.Fluorescence in O,K,J and I were different with different treatments.Effects of Cd and warming treatment on Fv/Fm and specific activity parameters were related to rice cultivars.Cd treatment did not significantly affect the Fv/Fm of Wuyungeng 30 and Xinliangyou 6,while single warming treatment significantly reduced Fv/Fm of Wuyungeng 30.Cd treatment significantly reduced specific activity parameters ABS/RC,DIo/RC,TRo/RC and ET0/RC of Xinliangyou 6(P＜0.05),while warming treatment significantly increased specific activity parameters of Wuyungeng 30.Single Cd treatment significantly reduced the aboveground weight of Xinliangyou 6,while single warming treatment significantly reduced the aboveground weight of Wuyungeng 30.However,the combined effects of Cd and warming on the biomass of rice varied with rice varieties.In conclusion,Cd and warming affect the biomass of rice by affecting the photosynthetic parameters and fluorescence parameters of rice,but the degree of influence varies with different cultivars.Among them,Wuyungeng 30 has strong resistance to Cd,while Xinliangyou 6 has strong resistance to warming.Therefore,suitable rice varieties should be selected in actual field management to cope with the effects of soil Cd pollution and temperature rise on rice growth.
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