【目的】研究银杏种子脱水敏感性及相关的生理生化变化,为银杏种子贮藏、种质资源的保存及苗木生产提供理论依据。【方法】银杏种子于25 ℃、湿度(25±2)%条件下脱水67 d,种子含水量每下降5%左右时随机取样测定相关生理生化指标。【结果】当种子含水量降至45.1%时,发芽率并未有明显变化,然而,当种子含水量降至40.1%时,发芽率从开始的92%下降至50%;相关性分析表明种子含水量与发芽率之间存在极显著的正相关(r=0.910)。银杏种子脱水过程中,其相对电导率不断上升。此外,SOD活性变化与POD活性的变化基本相似,均呈现出先下降,后升高至最大值,再下降的趋势,只是其POD活性的上升比SOD早,说明POD的反应比SOD更为敏感。种子含水量与硫代巴比妥酸反应产物(TBARS)含量(r=-0.619)、相对电导率(r=-0.745)之间存在极显著的负相关关系。【结论】银杏种子对脱水高度敏感,表现出顽拗型种子特点。严重脱水降低了银杏种子抗氧化酶活性,并加剧了膜脂过氧化作用,导致种子活力下降乃至完全丧失。

【Objective】 The aim of this work was to examine the superoxide dismutase (SOD) and peroxidase (POD) activity and germinability of Ginkgo biloba seeds in response to desiccation, to provide technical guidance for the preservation and storage of its germplasm resources. 【Method】 Seeds were placed in a drying room [(25±2)% relative humidity, 25 ℃)] for 67 days. Samples were randomly taken for germination testing and enzyme activity determination after each ±5% decrease in moisture content. 【Result】The germination percentage remained constant when the seed moisture content decreased from 48.0% (fresh seeds) to 45.1%. However, when the moisture content reached 40.1%, the germination percentage decreased from 92% to 50%. A significant positive correlation was observed between the moisture content and seed germination percentage (r = 0.910). The electrical conductivity was significantly higher during the initial desiccation period (48.0%-45.1%). Furthermore, both SOD and POD activity first reduced, and then increased to peak values before declining again. POD activity rose earlier than SOD activity, indicating that the POD reaction was more desiccation-sensitive than the SOD reaction. Significant negative correlations were observed between the moisture content and thiobarbituric acid-reactive substance content (r =-0.619) and electrical conductivity (r =-0.745). 【Conclusion】Our collective results suggest that G. biloba seeds are highly sensitive to desiccation. Excessive desiccation could reduce the antioxidant enzyme activity of G. biloba seeds and intensify membrane lipid peroxidation, which would cause a consequent reduction—or even a complete loss—of seed germinability.