Effects of high light and low temperature during harsh winter on needle photodamage of Abies mariesii growing at the forest limit on Mt. Norikura in Central Japan

Coniferous evergreen firs Abies mariesii (A. mariesii) growing at the forest limit (near 2500 m altitude) on Mt. Norikura (36degrees61'N, 137degrees33'E, 3026 in altitude) in Central Japan are exposed to severe winter-stresses. Under such conditions, only the abaxial side of A. mariesii needles changes from green to reddish-brown in early spring, resulting in the death of the needles. Since this needle damage is only observed in shoots that protrude from the snow surface and not in those buried in snow or located at lower elevations, this phenomenon seems to be caused by the interaction of strong sunlight reflected from the snow surface and low temperature. We found that the damaged needles have increased in the de-epoxidation state of xanthophyll cycle because they contained large amounts of zeaxanthin, which appears when the leaves encounter a strong light stress, leading to the long-term down-regulation of PS II photochemistry. These results indicate that the needles acclimatize against the strong light during severe winter. Furthermore, ascorbate peroxidase (APX, E.C. 1.11.1.11) activity was found to decrease remarkably during critical subzero periods, while superoxide dismutase (SOD, E.C. 1.15.1.1) activity remains constant throughout the year. Based on these results, we discuss herein how A. mariesii growing at the forest limit of temperate zone responds to high light and low temperature in harsh winter conditions. (C) 2003 Elsevier Science Ireland Ltd. All rights reserved.