CONTENT OF REDUCED GLUTATHIONE FORM AS A BIOMARKER OF OXIDATIVE STRESS IN SPINACH PLANTS GROWING IN SOIL CONTAMINATED WITH ZINC

The aim of the paper is the assessment of the efficiency of anti-oxidative system in spinach plants growing in the substratum polluted with zinc. The assessment was conducted on the basis of changes of reduced glutathione (GSH) form concentration in the plant aboveground organs. Spinach plants, ‘Matador’ c.v., were cultivated in soils contaminated with zinc in two pot experiments conducted in 2010 and 2011. The experimental substratum was light, slightly soil with granulometric composition of sandy silt loam. Zinc in the acetate form, was supplied to the soil in four doses corresponded to this metal critical concentrations in soil with 0, I, II and III degrees of pollution with this element according to IUNG classification. Simultaneously, the control with natural Zn content in soil was maintained. Zn concentrations in spinach ranged from 412.8 to 1722 mg ∙ kg-1 d.m. and increased with growing degree of substratum pollution with this element. Over the course of the vegetation period the content of Zn in plants was generally greater. GSH content in spinach grown in both years of experiments fluctuated from 31.70 to 238 µg ∙ g-1 f.m. The biggest content of this compound in spinach was stated in the initial phase of plants growth. The plants tolerated only the first two Zn doses supplied to the substratum. Spinach growing in the objects where zinc additions to the soil equalled II and III degree of substratum pollution died shortly after germination. The plants from these objects in the initial growth phase contained significantly less GSH than spinach from the objects with two first degrees (0 and I) of substratum pollution with zinc or from the control. The content of reduced glutathione form in spinach is a good biomarker of oxidative stress caused by zinc presence in plants. Synthesis of a bigger amount of GSH conditions spinach plant resistance to over the norm zinc content in soil. The efficiency of anti-oxidative system in spinach is bigger in the initial phase of this plant growth