Seasonal differences in xanthophyll cycle characteristics and antioxidants in Mahonia repens growing in different light environments

Abstract

We investigated differences between summer and winter in photosynthesis, xanthophyll cycle-dependent energy dissipation, and antioxidant systems in populations of Mahonia repens (Lindley) Don growing in the eastern foothills of the Colorado Rocky Mountains in deep shade, full exposure, and under a single-layered canopy of Pinus ponderosa (partially shaded). In summer, increasing growth irradiance (from deep shade to partial shade to full exposure) was associated with increased xanthophyll cycle-dependent energy dissipation in PSII and an increased capacity to detoxify reactive reduced oxygen species, as measured by increases in the activities of ascorbate peroxidase, superoxide scavenging, glutathione reductase, and monodehydroascorbate reductase, as well as increases in leaf ascorbate and glutathione content. Leaves of exposed and partially shaded plants exhibited decreased capacities for photosynthetic O evolution in winter compared to summer, while in the deeply shaded plants this parameter did not differ seasonally. Seasonal differences in the levels of antioxidants generally exhibited an inverse response to photosynthesis, being higher in winter compared to summer in the exposed and partially shaded populations, but remaining unchanged in the deeply shaded population. In addition, total pool size and conversion state of the xanthophyll cycle were higher in winter than in summer in all populations. These trends suggest that both xanthophyll cycle-dependent energy dissipation in PSII and the capacity to detoxify reactive reduced oxygen species responded to the level of excess light absorption.

Exogenous abscisic acid increases antioxidant enzymes and related gene expression in pepper (Capsicum annuum) leaves subjected to chilling stress

“…AsA was measured according to the method described by Logan et al (1998). Briefly, leaves (0.3 g) were homogenized with 0.9 mL ice-cold 6% HClO 4 and centrifuged at 12,000 rpm for 20 min at 4°C.…”

The role of antioxidant enzymes in photoprotection

“…Many long-lived evergreens respond to the onset of wintertime cold temperatures by decreasing chlorophyll content (Adams and Demmig-Adams 1994;Verhoeven et al 1996;Logan et al 1998c;Burkle and Logan 2003) and reorganizing their light harvesting antennae into an energy dissipating state (Gilmore and Ball 2000; Matsubara et al 2002;Adams et al 2002Adams et al , 2004. However, profound up-regulation of levels of antioxidants is another hallmark of acclimation to cold temperatures (Scho¨ner and Krause 1990;Anderson et al 1992;Mishra et al 1993;Logan et al 1998cLogan et al , 2003. Cold-induced increases in the levels of antioxidant enzymes compensate for the effect of lower temperatures on their activities and also presumably help cope with an enhanced rate of ROS formation (Lohrmann et al 2004).…”

Effects of Aluminum on Light Energy Utilization and Photoprotective Systems in Citrus Leaves

“…GSH and GSSG were determined according to Griffith (1980). AsA and DAsA were measured according to Logan et al (1998). Briefly, one leaf disc (1 cm 2 ) was ground in 1 mL of ice-cold 6 % (v/v) HClO 4 , the extract was centrifuged at 10 000 g for 10 min at 2 C and immediately used for measurements.…”