Light and excess manganese. Implications for oxidative stress in common bean


Gonzalez, A.; Steffen, K.L.; Lynch, J.P.


Plant Physiology, Volume 118, Issue 2, p.493-504 (1998)

Download Options:

Full Text:

Sorry, publisher does not permit download

My library :

openurl resolver


The effects of light intensity on antioxidants, antioxidant enzymes and chlorophyll content were studied in common beans ( Phaseolus vulgaris ) exposed to excess Mn. Leaves of bean genotypes contrasting in Mn tolerance were exposed to two different light intensities and to excess Mn; light was controlled by shading a leaflet with filter paper. After 5 days of Mn treatment ascorbate was depleted by 45% in leaves of the Mn-sensitive cv. ZPV-292 and by 20% in the Mn-tolerant cv. CALIMA. Nonprotein sulfhydryl groups and glutathione reductase were not affected by Mn or light treatment. Ten days of Mn-toxicity stress increased leaf ascorbate peroxidase activity of cv. ZPV-292 by 78% in low light and by 235% in high light, and superoxide dismutase activity followed a similar trend. Increases of ascorbate peroxidase and superoxide dismutase activity observed in cv. CALIMA were lower than those observed in the susceptible ZPV-292. CALIMA had less ascorbate oxidation under Mn-toxicity stress. Depletion of ascorbate occurred before the onset of chlorosis in Mn-stressed plants, especially in ZPV-292. Lipid peroxidation was not detected in floating leaf discs of mature leaves exposed to excess Mn. The results suggest that Mn toxicity may be mediated by oxidative stress, and that the tolerant genotype may maintain higher ascorbate levels under stress than the sensitive genotype.