Sugar, Starch, and Proline in Peach Trees Exposed to Freezing Temperatures during Dehardening

Abstract

Freezing temperatures cause different levels of freezing injury and change biochemical components of trees. In this study, the range of survival temperature and variation in electrolyte leakage, and in concentrations of sugar, starch, and proline were determined in peach twigs (Jinmi, Changhowonhwangdo, and Kawanakajima Hakuto) exposed to artificially controlled freezing temperature. Freezing temperatures at which the plants were damaged by stress were found to be - 21 &deg C in Jan. and Feb., - 18 &deg C in Mar., and - 6 &deg C in Apr. Electrolyte leakage increased as temperature decreased from - 15 &deg C to - 24 &deg C at each assessment time. Sugar gradually decreased after the endodormancy period in the late part of winter, and sugar concentration was overall lower in freezing temperature treatments, while starch increased as a result of changing seasons from Jan. to Apr. The trend of proline concentration was related to the survival rate of peach trees during winter. This study suggests possible safe temperatures for survival and cultivation of peach trees as well as identifying freezing temperature effects on internal components of freeze-injured peach twigs.