| Abstract: | The production of superoxide radical ( ) was studied in roots of cotton (Gossypium hirsutum L. cv. Deltapine15/21), bean (Phaseolus vulgaris L. var. Pr?lude) and tomato(Lycopersicon esculentum L. cv. Super marmande) plants grownin nutrient solution with different Zn concentrations. UsingTiron as a spin-probe, electron spin resonance (ESR) was employedfor the measurements of  levels. In the 48 000 g and 140 000 g supernatants of cotton root extracts theamplitude of the Tiron ESR signals reflecting production steeply increased with the appearance of visual Zndeficiency symptoms in the shoots. The changes in the amplitudeof the Tiron ESR signals were closely correlated with an NADPH-dependent generating oxidase activity with a high pH optimum. Increases in NADPH-dependent generation were also found in root extracts of Zn-deficientbean and tomato plants. In all experiments re-supply of Zn todeficient plants for 12 h or 24 h markedly decreased generation. Further, with advancing Zn deficiencyrates of NADPH oxidation increased and the activities of superoxidedismutase (SOD) and catalase decreased. The results suggest that cotton, bean and tomato roots possessan NADPH-dependent generating activity which is affected by the Zn nutritional status of the plants. UnderZn deficiency, enhanced generation and impaired detoxification of Of and H2O2 could lead to elevated levelsof and -derived oxidizing O2 species and thus to increased peroxidation of membrane lipids. Key words: NADPH oxidase, superoxide radical, zinc deficiency |
