Antioxidant Enzyme Activity in the Leaves of <i>Lonicera caerulea</i> along an Altitude Gradient on the North Slope of Changbai Mountain

Abstract

Changes in the activity levels of the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and ascorbate peroxidase (APX) in the leaves of Lonicera caerulea, a perennial deciduous shrub, were measured along an altitude gradient (800-1800 m) on the northern slope of Changbai Mountain, China. Enzyme activity levels were statistically analyzed with respect to various environmental factors'including soil and climate parameters' to explore the physiological and biochemical mechanisms underlying the adaptation of this shrub to mountainous habitats. From 800 m to 1000 m, POD activity decreased significantly (to 712 U/g•min), then increased significantly to peak at 1600 m (4190 U/g•min), followed by a decrease at 1800 m. The CAT activity increased significantly from 800 m to peak at 1600 m (274 U/g•min), followed by a decrease at 1800 m. SOD activity increased steadily from 800 m to 1800 m. From 800 m to 1000 m, APX activity decreased significantly (to 5201 U/g•min), then increased significantly to peak at 1600 m (14771 U/g•min), followed by a decrease at 1800 m. Multiple regression analysis showed that CAT activity was mainly affected by the number of days with snow cover, soil available P, and soil total P. SOD activity was mainly affected by precipitation from June to September and soil total P. APX activity was mainly affected by soil available P. Correlations between leaf traits and environment indicated that all four enzymes were sensitive to environmental changes, and that enzyme activity levels adjusted to the environment as the elevation changed. The results here showed, antioxidant enzyme activity levels in the leaves of L. caerulea on the northern slope of Changbai Mountain were lower at low altitudes (800-1200 m) and higher at moderate altitudes (1200-1600 m), suggesting that these altitudes are the most conducive to the stable growth of. L. caerulea has high edible and medicinal value, and this plant grows well throughout its wide distribution in the Changbai Mountain area. Therefore, the results of this study suggested that