【目的】探索温度影响白皮松(Pinus bungeana)种子萌发过程中水分、储藏物质含量和酶活性变化的生理机制,以揭示温度影响种子萌发的生理机制。【方法】将白皮松种子置于不同温度下进行萌发试验,检测温度对发芽率和萌发过程中含水率、可溶性糖、淀粉、蛋白质、粗脂肪含量及淀粉酶、蛋白酶和酸性磷酸酶活性等生理指标的影响。【结果】萌发温度为15和20 ℃时,种子发芽率达90%左右;当萌发温度升高到25和30 ℃,种子萌发受阻,发芽率急剧降至10%以下。20 ℃条件下,种子萌发过程水分含量变化分为快速升高期、滞缓期和重新快速升高期3个阶段;萌发过程中,种子内的物质代谢活动较为强烈:可溶性糖含量先降低后升高,6 d后淀粉开始水解,10 d后脂肪和蛋白质在相关酶的作用下分解为小分子物质供胚利用。25 ℃条件下,种子吸水始终停留在滞缓期;过高的温度抑制了酸性磷酸酶、淀粉酶和蛋白酶的活性,影响了脂肪、淀粉和蛋白质的降解;可溶性糖含量有所降低以维持种子“静止”状态。【结论】白皮松种子萌发的适宜温度条件为15~20 ℃,温度继续升高会产生热抑制;适温条件下(20 ℃),种子萌发优先利用胚自身贮藏的物质,最先利用的是碳水化合物,然后是蛋白质和脂类的动员,且脂肪大量降解始于胚根突破种皮后。高温25 ℃条件下,种子中的酶活性被抑制,物质分解代谢受阻,胚不能吸收和利用足够的营养来完成萌发。

【Objective】The study explored the changes of water content, storage substance content, and enzyme activity during the germination process of Pinus bungeana seeds, in order to reveal the physiological mechanism of temperature that affects the seed germination. 【Method】Seed germination was performed at various temperatures to study the effects of temperature on the extent of germination. Physiological indicators, such as the content of water, soluble sugar, starch, soluble protein, crude fat and the activities of amylase, protease and acid phosphatase were measured during the germination process. 【Result】A high germination percentage (approximately 90%) was obtained when the seeds were cultured at 15 and 20 ℃. As the culture temperature continued to rise to 25 and 30 ℃, the radicle protrusion and seed germination were seriously hindered, resulting in a sharp drop in germination percentage to <10%. At 20 ℃, the change of water content during germination could be characterized into three stages: rapid increase, period of retardation, and another rapid increase. During germination, the catabolism and anabolism of substances occurred vigorously in the seeds. The soluble sugar content initially decreased and then gradually increased. As starch began to hydrolyze with a decreased content after six days of cultivation, the crude fat and soluble protein were degraded into small molecules as catalyzed by the corresponding enzymes for embryo utilization after 10 days of cultivation. At 25 ℃, the water absorption process of seeds stayed in the retardation period throughout. At this incubation temperature, the activities of acid phosphatase, amylase, and protease in seeds was inhibited due to the excessive temperature, thus affecting the degradation of crude fat, soluble protein and soluble starch. In addition, the soluble sugar content was slightly decreased to keep the ‘still’ state of the seeds with low consumption. 【Conclusion】The suitable temperature range for seed germination of P. bungeana was 15-20 ℃. However, if the temperature continued to rise, seed germination was hindered and thermal inhibition occurred. At the favorable temperature of 20 ℃, seeds would preferentially use the nutrients stored in the embryo when germination occurred. Carbohydrates are first decomposed and utilized, followed by the mobilization of proteins and lipids. Degradation of a large amount of fat began after the radicle broke through the seed coat. At a high temperature of 25 ℃, the activity of enzymes in the seeds was inhibited, resulting in the catabolism of macromolecular substances was hindered. Ultimately, the embryo could not absorb and utilize enough nutrients to complete the germination process.