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Stress tolerance and stress-related metabolite concentrations were determined over different seasons in leaves and stems of sea buckthorn, which is believed to be a highly stress-tolerant plant compared with major deciduous fruit trees. Electrolyte leakage in sea buckthorn leaves reached a minimum of 20% or less at 51 °C, with an increase in temperature. In contrast, electrolyte leakage in sea buckthorn stems was less than 20% at −40 °C, during the coldest period, and was almost undetectable in January. A change in heat tolerance corresponded to an alteration of tocopherol concentration, whereas a change in freezing tolerance corresponded to changes in raffinose and ascorbic acid concentrations, which indicated winter-specific production, along with sucrose and glucose. Heat, drought, and freezing tolerance in sea buckthorn were higher than those in apple and pear; the higher heat and freezing tolerance may be related to tocopherol and sucrose and ascorbic acid concentrations, respectively. Because few studies have simultaneously investigated multiple stresses and metabolites across different seasons, this study, particularly involving the dramatic accumulation of ascorbic acid in winter and the role of tocopherol in heat tolerance, will provide new insights into a comprehensive understanding of stress acclimation in fruit trees. |
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