红松种子休眠解除的光、温调控机制

Pinus koraiensis, the relic plant of the tertiary period, is the dominant and constructive species of broadleaved Korean pine forest that is one of the temperate typical climax communities. However, around 90% of the original broadleaved Korean pine forest has been degraded into the temperate broadleaved secondary forest due to human and natural disaster disturbances. The lack of the dominant tree species, P. koraiensis, is the prominent problem in broadleaved secondary forests. Improving natural regeneration ability of P. koraiensis is fundamental for the recovery and positive succession of secondary forests. Abundant and viable seeds germinate successfully are essential for the regeneration process of P. koraiensis. However, the deep primary and secondary dormancy of P. koraiensis seeds basically blocks the regeneration process. Thus, the experiments in both laboratory and field will be designed to explore the effects of light and temperature on the development of embryo, the seed afterripening and the germination process. Furtermore, the variation in endogenous hormone, respiration metabolism and proteome in seeds will be compared under different light and temperature conditions. The objectives of this project are as follows: 1) to illuminate the regulation mechanisms of light and temperature on seed dormancy release in P. korainensis seeds based on the molecular biology; 2) to find out the appropriate light and temperature conditions to promote seed dormancy release in P. koraiensis by adjusting the forest structure. The results will certainly have important theoretical and practical significances for promoting natural regeneration of P. koraiensis, and finally realizing the recovery and sustainable development of broadleaved Korean pine forests.

红松为第三纪孑遗植物，是温带典型地带性顶级群落之一——阔叶红松林（60%分布在我国东北）的建群种。由于受人为和自然灾害强烈干扰，90%的原始阔叶红松林退化为阔叶次生林，其最显著的退化特征是优势树种红松缺失，因此，提升红松的天然更新能力是实现次生林正向演替的根本途径。充足、有效萌发的红松种子是红松更新的关键，但是，红松种子的深休眠和二次休眠等特征，成为红松更新过程中的首要障碍。本项目拟采用室内控制和野外模拟相结合的方法，重点研究光、温对红松种胚发育、种子后熟和种子萌发过程的影响；探讨不同光、温条件下红松种子内源激素、呼吸代谢和蛋白质组学等特征变化，从分子生物学水平上系统揭示红松种子原生休眠和次生休眠形成与解除的光、温调控机制，通过林分结构调控促进红松种子的休眠解除。研究结果将丰富森林种苗学，对指导人工促进红松天然更新、实现阔叶红松林恢复和可持续发展具有重要理论与现实意义。

红松是温带地区地带性顶级植被——阔叶红松林的建群种和优势种。红松种群天然更新差是阔叶红松林退化为次生林的主要原因。种子深休眠性是阻碍红松种群更新的一大障碍。本项目以光、温影响机制为研究主线，通过控制红松种子后熟阶段和种子萌发过程中的光照和温度条件，测定了不同阶段不同光温条件下红松种子萌发指标、种子内源激素水平和蛋白质组动态变化。主要结果如下：.（一）种子后熟阶段光照和温度对红松种子休眠和萌发的影响：温度是影响红松种子休眠解除的重要因素，光对红松种子休眠解除的影响不大；红松种子休眠解除与层积温度引起种子内ABA水平的下降密切相关；一定的层积温度下，光照诱导种胚内ABA水平下降或GA/ABA水平上升，促进了红松种子萌发；红松种子休眠解除主要的代谢通路是谷胱甘肽代谢和核糖体通路，说明休眠解除过程中有大量抗性基因表达和蛋白质合成。谷胱甘肽通路包含细胞分化，保护细胞免受外源物质及活性氧伤害。.（二）萌发培养阶段光照和温度对红松种子休眠和萌发的影响：相同生境条件下，清原红松种子萌发率均显著高于长白山和伊春种子，长白山和伊春红松种子需要更高的积温以解除休眠；野外林分下，红松种子春、夏季不萌发或萌发率低，不适宜种子萌发；三种源种子夏季在林窗下萌发率均显著高于林下，红松种子萌发具有需光性；25 ℃为红松种子萌发的适宜温度，适宜温度下红松种子呈现出明显的萌发需光性；光照促进种子内（种皮、种胚和胚乳）GA3合成和种皮ABA降解，促进了种子萌发；红松种子萌发前后启动了大量的氧化还原反应，一些抗氧化和解毒功能的蛋白酶合成；光照通过促进叶绿体以及色素体构建促进了红松种子的萌发进程。实际林分下，应适时(春、夏季)对林分进行透光处理，改善林下光环境，可促进林下红松种子萌发，完成种群天然更新。