Seasonal differences in xanthophyll cycle characteristics and antioxidants in Mahonia repens growing in different light environments |
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Authors: | Barry A Logan Stephen C Grace William W Adams III Barbara Demmig-Adams |
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Institution: | (1) Department of Environmental, Population, and Organismic Biology, University of Colorado, Boulder, CO 80309-0334, USA e-mail: william.adams@Colorado.EDU; Fax: +1 (303) 492-8699, US |
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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 O2 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.
Received: 23 October 1997 / Accepted: 23 March 1998 |
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Keywords: | Antioxidants Cold acclimation Mahonia repens Photoprotection Xanthophyll cycle |
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