【目的】娜塔栎以种子繁殖为主,但该种子对脱水敏感,不易运输和贮藏,分析娜塔栎种子失水过程中的生理变化,为揭示娜塔栎种子不耐脱水机制提供理论依据。【方法】以娜塔栎种子为材料,分别测定种子含水率为39.6%、35.0%、30.0%、25.0%、20.0%、15.0%、13.0%时的发芽率和超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、脯氨酸、糖类物质、可溶性蛋白、丙二醛(MDA)等生理指标,将发芽率与各处理所测指标进行相关性分析,探讨娜塔栎种子不耐脱水的原因。【结果】当含水率高于25.0%时,种子发芽率在90.0%以上;之后随种子失水程度增加,发芽率不断下降:含水率下降至15.0%时,发芽率仅为38.3%;含水率下降至13.0%时,发芽率为0.0%。对种子发芽率(y)和含水率(x)进行拟合后得到关系方程y = 0.016 5x³- 1.553 6x² + 47.84x - 392.03,计算得出种子的临界含水率为21.4%,半致死含水率为16.7%。娜塔栎种子失水过程中MDA含量不断增加。失水初期,抗氧化酶系统中SOD活性不断增强,在含水率低于25.0%时,SOD活性迅速下降;随含水率降低,CAT活性持续下降,含水率为25.0%时显著下降。随含水率降低,渗透调节物质脯氨酸、可溶性糖、蔗糖均呈现先上升后下降的变化趋势,脯氨酸及蔗糖均于含水率20.0%时达到最大值,可溶性糖则于含水率15.0%时达到最大值;还原糖含量持续增加;可溶性蛋白含量呈下降趋势,但各失水阶段差异不显著。相关性分析表明,种子发芽率与SOD、CAT活性呈显著正相关,与还原糖、MDA、脯氨酸、可溶性糖、蔗糖含量呈显著负相关。【结论】娜塔栎种子不耐脱水,在运输、贮藏种子时其含水率应维持在21.4%(临界含水率)以上,最低不能低于16.7%(半致死含水率)。娜塔栎种子失水初期,SOD活性增强,渗透调节物质脯氨酸、蔗糖、可溶性糖含量增加,对娜塔栎种子抵御失水胁迫有重要作用。失水过程中CAT活性、可溶性蛋白含量不断下降,以及MDA、还原糖持续积累,可能是导致娜塔栎种子对脱水敏感的重要原因。

【Objective】Quercus texana is primarily propagated via seeds, but these are highly sensitive to dehydration, which limits their transport and storage potential. This study investigated the physiological changes occurring during seed desiccation to elucidate the mechanisms underlying their intolerance to dehydration. 【Method】Seeds of Q. texana were analyzed at moisture contents (WC) of 39.6% (fresh seeds), 35.0%, 30.0%, 25.0%, 20.0%, 15.0%, and 13.0%. Germination percentages and physiological parameters, including superoxide dismutase (SOD), catalase (CAT), proline, saccharides, soluble proteins, and malondialdehyde (MDA), were measured to explore the effects of desiccation. 【Result】When the WC exceeded 25.0%, the germination percentage remained above 90.0%. However, as the dehydration of Q. texana seeds progressed, the germination percentage progressively declined, reaching 38.3% at a WC of 15.0%. Further reduction in WC to 13.0% resulted in the complete inhibition of germination, with the percentage falling to 0.0%. The regression model (y = 0.016 5x³ - 1.553 6x² + 47.84x - 392.03) established critical and semilethal WC at 21.4% and 16.7%, respectively. MDA levels increased continuously during desiccation, indicating heightened lipid peroxidation. SOD content exhibited an initial rise, followed by a sharp decline at 25.0% WC, while CAT activity exhibited a consistent decline, accelerating below 25.0% WC. The levels of osmoregulatory substances, such as proline and sucrose, increased up to 20.0% WC but decreased thereafter. The soluble sugars peaked at 15.0% WC, while reducing sugars steadily increased. The soluble protein content declined, though this decline was not statistically significant across desiccation stages. Correlation analysis revealed a significant positive relationship between germination percentage and SOD and CAT activities, and a negative relationship with MDA, reducing sugar, proline, soluble sugar, and sucrose levels. 【Conclusion】Q. texana seeds demonstrated a high level of intolerance to dehydration, necessitating a minimum WC of 21.4%, preferably above 16.7%, for safe transport and storage. It was observed that initial dehydration stress is mitigated by enhanced SOD activity and increased osmoregulatory substances such as proline, sucrose, and soluble sugars. However, the progressive decline in CAT activity and soluble proteins, combined with MDA accumulation and rising reducing sugars, compromises seed viability under prolonged desiccation.