Characteristics of Antioxidant Responses of Mangifera indica Leaves by Enhanced UV-B Radiation

Abstract:

In order to understand the mechanism of antioxidant responses of mango leaves to enhanced UV-B radiation, the adult trees of Mangifera indica ‘Tainong No. 1’ were treated with enhanced UV-B radiation of 24 and 96 kJ/(m²·d), respectively, with the natural sunlight as control (CK), and the dynamic changes in physiological and biochemical indexes were studied. The results showed that MDA content, relative electrical conductivity, net photosynthetic rate, antioxidant enzyme activities, contents of polyphenols, Vc and mangiferin in leaves treated with 24 kJ/(m²·d) UV-B were not significantly different from CK, while flavonoids and reduced GSH contents were significantly higher than CK. MDA content, relative electrical conductivity, antioxidant enzyme activities, polyphenols, flavonoids, reduced GSH, mangiferin and other reduced protective components were significantly higher than CK treated with 96 kJ/(m²·d) UV-B, while net photosynthetic rate and Vc content were significantly lower than CK. Therefore, the adult mango trees has not been injured under 24 kJ/(m²·d) UV-B, probably through increasing the content of flavonoids and reduced GSH to scavenge reactive oxygen species. The leaves were damaged by reactive oxygen species treated with 96 kJ/(m²·d) UV-B, but it could still reduce the damage by two mechanisms, at first, enhancing the activities of antioxidant enzymes, such as SOD, POD, CAT, and increasing the contents of reducing components, such as polyphenols, flavonoids, reduced GSH, Vc and mangiferin, at the second, mangiferin, flavonoids and reduced GSH could absorb UV-B radiation.