ASSAY OF THE THIOBARBITURIC ACID-REACTIVE PRODUCTS OF LIPID-PEROXIDATION IN PLANTS USING DERIVATIVE ABSORPTION-SPECTROSCOPY

The spectrophotometric determination of 2-thiobarbituric acid-reactive products of lipid peroxidation in plants is limited because of the presence of substances forming coloured complexes with the reagent as well as water-soluble pigments. In order to overcome this interference 2nd derivative analysis of the absorption spectra was applied. The results of the study indicate that the method can be performed using cotton and maple leaves that contain high amounts of anthocyanins and bifunctional aldehydes, respectively. The accumulation of lipid peroxidation products was observed in cotton plants treated with the herbicide diquat. In wheat roots the band of malondialdehyde-thiobarbituric acid absorption was not resolved either in intact or in diquat-treated plants, because of the production of a chromophore with an absorption maximum at 551 nm. The sensitivity of the 2nd derivative determination of malondialdehyde is about 0.2-mu-M. A linear response was observed up to 8-10-mu-M of the aldehyde.