低温生物工学会志〔CryobiologyandCryotechnology〕，Vol.docVIP

低温生物工学会誌〔Cryobiology and Cryotechnology〕，Vol. xx, No. x, xxx～xxx, 2014 Influence of the Freeze-thaw Process under Acid Conditions on the Viability of Wintering Plants Hidetoshi INADA, Seizo FUJIKAWA, Keita ARAKAWA Division of Environmental Resources, Graduate School of Agriculture, Hokkaido University, Sapporo 060-8589, Japan Acid precipitates in snow may be a stress factor that affects the growth of wintering plants. The objective of this study was to determine the influence of acid-snow stress on leaves of wintering plants by in vitro experiments. Three different experiments, equilibrium freezing, prolonged freezing and repeated freeze-thawing, were carried out in order to simulate freeze-thawing of acid snow during winter. The results showed that acidification in the process of freeze-thawing caused enhancement of freezing injury of wintering plants. 　　　　　　 (Received Xxx. xx, 20xx; Accepted Xxx. xx, 20xx) INTRODUCTION It has been observed in the past decade that pH of meltwater of snow has become more acidic than pH of pure water (pH 5.6), which dissolved saturated carbon dioxide, as well as pH of acid rain or mist1-3), indicating precipitation of acid snow during winter. Acid snow is thought to be completely different from acid rain or mist since acid substances in snow or ice crystals may be partly concentrated, especially in the surface and central part of granular snow during winter4-6). At the early and/or late stages of snowmelt, meltwater with relatively strong acidity due to acid substances on ice crystals may be released from acid snow layers into soil, streams and lakes1,7). Wintering plants covered with acid snow may be subjected to freezing stresses, caused by reduction in freezing temperature or exposure to a prolonged subzero temperature during mid-winter, and freezing stresses caused by repeated freeze-thawing in early winter and/or early spring, in the presence of concentrated acid substances in snow or ice crystal