Photosynthetic Rate and Lipid Peroxidation of Cultivated (Glycine max L.) and wild Soybean (G. tomentella L.) Exposed to Drought Stress and Paraquat

Abstract

Oxidative stress of three soybean (Glycine max, (L.) Merr) cultivars and a wild line soybean (G. tomentella) were analyzed in response to drought and paraquat treatment. Drought treatment was performed by withholding water for 12 days (for cultivars) and 22 days (for wild line soybean) in greenhouse experiment during flower initiation. Paraquat treatment was applied using manual sprayer at the same time of drought treatment application. Plant water status and photosynthetic rate were measured every three days during the drought treatment and 2 days after rewatering, and during 5 days after paraquat application. During the treatment, malondialdehyde (MDA) was analyzed to study lipid peroxydase activity. Drought treatment decreased plant relative water content up to 33% and 42% in sensitive and tolerant variety,respectively.. Transpiration and photosynthetic rate decreased almost to zero at the end of drought period, while those of control plant were 4.7 µmol m-2 s-1 and 12.58 µmol m-2 s-1, respectively. Malondialdehyde content increased dramatically (5890 nmol/g fresh weight) on drought stressed plant as well as on paraquat treated plant as compared to control plant (3281 nmol/g fresh wight). It indicated that plants underwent oxidative stress due to severe drought stress.