红松种子延迟萌发的机制研究

Mixed broadleaf Korean pine (Pinus koraiensis Sieb. et Zucc.) forest (MBKPF) is the zonal climax vegetation type of temperate forests in Northeast China. The distribution area of MBKPF has now been largely declined. Korean pine (Pinus koraiensis Sieb. et Zucc.) is a dominant tree species of MBKPF. The successful regeneration of Korean pine is important for the restoration of MBKPF. Korean pine seeds disperse in early-Autumn and delay germination until spring of the first year and second year following dispersal, respectively. A delay in germination time retards the regeneration of Korean pine. The germination time is mediated by seed dormancy status. However, the patterns of seasonal changes in seed dormancy status and the regulatory mechanism of dormancy status are still unclear. This will hinder our more insights into the mechanisms of seed germination time and seed regeneration. Korean pine seeds are selected as the object of this study. The filed burial experiment and laboratory control experiment are combinely conducted to determine the filed germination percentage, laboratory germination percentage, the contents of phytohormones, the sensitivity of seeds to phytohormones, reserves mobilization and metabolic pathways. The specific objectives of this project are as follows: 1) to elucidate the patterns of seasonal change of seed dormancy status; 2) to determine the effects of temperature on the seasonal changes of seed dormancy status; 3) to analyze the roles of phytohormones and metabolic pathways in the seasonal changes of dormant status; and 4) to reveal the mechanisms of the delay in seed germination. The results of the present study provide some important theoretical guidelines for artificially promoting the natural regeneration and the restoration of MBKPF and applying sustainable management of MBKPF.

阔叶红松林是中国东北温带森林的地带性顶极植被类型，现已大面积退化，主要建群树种红松的成功更新是其恢复过程中最重要的一步。当年秋季落下的红松种子分别延迟到第二年和第三年的春季完成萌发。萌发时间的延迟阻碍红松更新。种子休眠状态调控萌发的时间。但目前尚不清楚红松种子休眠状态的季节性变化规律及其原因，这将对深刻认识种子萌发时间的调节机理和更新机制产生影响。本项目以阔叶红松林优势树种红松的种子为对象，通过野外埋藏实验和室内控制实验，重点研究种子的野外萌发率、室内萌发率、植物激素的含量、种子对植物激素的敏感性、储藏物质动员情况和代谢途径，阐明种子休眠状态的季节性变化特征，明确温度对种子休眠状态季节性变化的影响，综合分析植物激素和代谢途径在种子休眠状态季节性变化中的作用，揭示种子延迟萌发的机制。研究结果为人工促进阔叶红松林天然更新，实现阔叶红松林植被恢复与可持续经营提供重要理论参考。

红松种子延迟萌发的特性，阻碍其天然更新以及退化阔叶红松林生态系统的恢复。本项目通过野外埋藏种子实验和室内控制实验，研究红松种子休眠状态的季节性变化规律，及其激素和代谢调节机制。主要研究结果如下：（1）当年秋季落下的红松种子具有形态生理休眠。在种子落下的第一个冬季，原生生理休眠逐渐解除；在第一个夏季，次生生理休眠被诱导；在第二个秋、冬季，次生生理休眠被解除；在第一个夏季，形态休眠缓慢解除，而在第二个早、中秋季，形态休眠快速解除；在第二个春季，种子的形态生理休眠完全解除。（2）随着层积温度降低（10 ℃、5 ℃和0 ℃），层积时间延长（2周、4周、5.5个月和6.5个月），种子萌发的温度范围逐渐加宽，原生生理休眠逐渐解除。（3）种胚中脱落酸含量的增加诱导种子在夏季进入次生生理休眠，而种子对脱落酸的敏感性降低导致其在秋、冬季逐渐解除次生生理休眠；种子对赤霉素的敏感性并未在其休眠状态变化中发挥调节作用；和“胚轴+子叶”相比，胚根中脱落酸的累积维持种子的原生生理休眠；在胚根中，脱落酸主要通过减弱与赤霉素生物合成有关的萜类化合物骨架生物合成途径，与种子抗氧化功能有关的谷胱甘肽代谢，而在“胚轴+子叶”中，脱落酸主要通过减弱糖酵解途径和甘油磷脂代谢途径，抑制萌发。（4）胚根中茉莉酸、茉莉酸-异亮氨酸、反式玉米素核苷、顺式玉米素核苷、异戊烯基腺嘌呤核苷和香蒲甾醇，“胚轴+子叶”中的反式玉米素和顺式玉米素无法显著累积，维持种子原生生理休眠。（5）和雌配子体相比，种胚中的碳水化合物代谢和氨基酸代谢在种子原生生理休眠维持中发挥重要作用。和“胚轴+子叶”相比，胚根中的碳水化合物代谢途径高效运行维持种子的原生生理休眠。该研究将丰富形态生理休眠种子休眠状态季节性变化机制的研究方法与理论，为实现阔叶红松林的天然更新与可持续经营提供重要理论支撑与实践参考。