Glutathione counteracts the inhibitory effect induced by cadmium on photosynthetic process in soybean

In soybean seedlings, Cd²⁺ affected growth and inhibited photosynthesis. Both the length and fresh mass decreased more in roots than in shoots. Cd₂₊ stress caused an increase in ratio of chlorophyll (Chl) (a+b)/b by 1.3 fold and ratio of total xanthophylls/β-carotene by 3 fold compared to the control. A reduced activity of photosystem 2 by about 85 % measured in Cd₂₊-treated chloroplasts was associated with a dramatic quenching of fluorescence emission intensity, with a band shift of 4 nm. A major suppression of absorption was accompanied with shift in peaks in the visible region of the spectrum. In Cd₂₊-treated chloroplasts a selective decline in linolenic acid (18:3), the most unsaturated fatty acid of chloroplasts, paralleled with the ten fold enhancement in ethylene production. A three fold increase in peroxidase activity was found in chloroplasts treated with Cd₂₊ compared to the control . Addition of 1 mM glutathione (GSH) counteracted all the retardation effects in soybean seedling growth induced by Cd₂₊. Thus GSH may control the Cd₂₊ growth inhibition as it detoxifies Cd₂₊ by reducing its concentration in the cytoplasm and removing hydrogen peroxide generated in chloroplasts. This revised version was published online in September 2006 with corrections to the Cover Date.