Seasonal Photoprotective Responses in Needles of Korean Fir (Abies koreana) Over an Altitudinal Gradient on Mount Halla, Jeju Island, Korea

Abstract

Chloroplast pigments and chlorophyll fluorescence were characterized in needles of Korean fir (Abies koreana) in summer, winter, and spring at three altitudes on Jeju Island, Korea. High light-harvesting efficiency (intrinsic photosystem II efficiency) and indirect evidence for high photosynthetic rates (high levels ofβ-carotene and chlorophyll b) during the growing season contrasted with mid-winter downregulation of light-harvesting efficiency involving retention of high zeaxanthin levels and locked-in photoprotective thermal dissipation (from low chlorophyll fluorescence emission). Neoxanthin levels were inversely correlated with sustained photoprotection in the winter, and lutein to xanthophyll cycle carotenoid levels decreased from summer to winter, suggesting that zeaxanthin plays the prominent role in winter photoprotection of Korean fir needles. Summer was apparently most conducive to photosynthesis, consistent with high levels of summer precipitation on Jeju Island, and in contrast to fir and other conifers in a climate with dry summers at high altitudes in Colorado, U.S.A., where studies have shown that the wet spring is the season most favorable for photosynthesis. Lastly, despite there being only 300 m difference in altitude among the three sites, there were discernible differences in (i) accumulation of zeaxanthin in winter (as an indicator for the severity of conditions, with highest levels at the highest altitude), (ii) apparent photosynthesis rates in summer (from β-carotene levels, with highest levels at the highest altitude), and (iii) transition to increased photosynthesis in spring (from fluorescence emission levels, slowest at the highest altitude).