Oxidative stress occurs during soybean nodule senescence

Several markers of oxidative stress were measured in 2- to 10-week-old soyb ean (Glycine max [L.] Merr.) nodules. There were increases in peroxides, pr otein carbonyls and modified DNA base concentrations with nodule age, The c atalytic iron content also increased significantly during nodule ageing. Ir on contained in the peribacteroid space was effective in promoting lipid pe roxidation and this might contribute to the degradation of the peribacteroi d membrane in senescing nodules, The concentration of the oxidized forms of glutathione and homoglutathione increased significantly during nodule deve lopment and the concentration of reduced glutathione and homoglutathione de creased during senescence. Taken together, these results are consistent wit h the development of oxidative stress in senescing nodules. Significant DNA and protein damage also occurred in the first days of nodule development, suggesting that an earlier period of oxidative stress might occur in the pe riod over which the symbiosis becomes established.