封冻前阻滞无叶假木贼种子萌发的机制及其萌发幼苗越冬抗冻机理

Seed germination and seedling growth are crucial stages of desert plant life strategy in the arid and semi-arid area, which directly determines establishment and regeneration of plant population. Research about seed germination of desert plant is widely reported. But, germination behavior of Anabasis aphylla seed before freezing and frost resistance mechanism of its seedling are less involved. Especially, frost resistance of desert plant seedling in winter has important ecological significance for climatic fluctuation and change in desert area. Anabasis aphylla is one of main constructive species of earthy desert area in Junggar basin, and has important role on maintaining water and soil safe of diluvial fan and plain. Furthermore, it is one resource plant species with great value. Through method of combining field investigation and observation with simulation experiment, project is carried out. First, characteristic and process of Anabasis aphylla seed germination before freezing are researched, which will reveal ecological mechanism and meaning of seed germination block under the condition of climatic change. Second, frost resistance mechanism of seedling in the different developmental stages in winter is studied, and ecological safety of seedling will be illuminated, which will discuss the potential meaning of seed germination before freezing for growth and regeneration of Anabasis aphylla seedling. This project can get a better understanding about adaptation mechanism of desert plant, has profound guiding significance on protection of resource plant and vegetation restoration in the desert area.

种子萌发和幼苗生长是荒漠植物生活史中的关键阶段，直接决定着植物种群的建立与更新。有关荒漠植物种子萌发的研究已有大量报道，但是对封冻前无叶假木贼种子萌发现象及萌发幼苗越冬抗冻机理的研究涉及较少，而荒漠植物萌发幼苗的越冬抗冻性对于应对荒漠区气候变化具有重要的生态学意义。无叶假木贼是准噶尔盆地土质荒漠的建群种，对维护山前洪积扇的水土安全具有非常重要的作用，而且也是一种利用价值较高的资源植物。本项目拟采用野外定点观测与人工模拟相结合的方法，分析封冻前无叶假木贼种子萌发的过程和特性，揭示阻滞种子萌发的环境机制，探讨气候变化条件下阻滞无叶假木贼种子萌发的生态意义；研究不同发育阶段无叶假木贼萌发幼苗的越冬抗冻性，阐明无叶假木贼萌发幼苗越冬抗冻机理，探讨全球气候变化对无叶假木贼萌发幼苗安全越冬的影响。项目研究能够加深对荒漠植物适应机制的理解，对荒漠区资源植物保护和植被恢复具有指导意义。

由于气候变化和人为活动的影响，荒漠幼苗自然更新困难，因此研究荒漠种子萌发特性和幼苗适应机制对荒漠区植被恢复具有重要意义。荒漠植物生存于极端严酷的环境条件下，有其特殊的种子萌发和幼苗更新机制，并且不同植物种子萌发过程对逆境胁迫的适应性很大程度上影响着植物的生长发育。目前，对封冻前无叶假木贼种子萌发现象及萌发幼苗越冬抗冻机理的研究涉及较少，而荒漠植物萌发幼苗的越冬抗冻性对于应对荒漠区气候变化具有重要的生态学意义。项目主要结论：1）梭梭和无叶假木贼荒漠种子在不同温度下均可萌发，随着温度的降低，初始萌发时间随之延长，种子的萌发速率及萌发指数随之降低，但最终萌发率无显著差异，并且各温度下的最终萌发率均达到90%。通过积温效应分析，确定了无叶假木贼和梭梭种子萌发的最低温度分别为0.54℃和0.79℃，积温值分别为9.89℃•d 和7.26℃•d。2) 无叶假木贼和梭梭种子不同萌发阶段的低温耐受特征大致相同，表现为吸胀（Ⅰ）和露白（Ⅱ）阶段对低温的耐受性较强，而脱去种皮（Ⅲ）和伸长生长（Ⅳ）阶段随着温度的降低，存活率急剧下降。随着低温萌发的进行，无叶假木贼种子中POD和可溶性蛋白呈先升高后降低的趋势，SOD和CAT活性呈逐渐降低的趋势，MDA和可溶性糖呈逐渐升高的趋势。3)无叶假木贼四个发育阶段进行转录组测序，有2787个共下调表达的基因，主要包括编码细胞色素P450，BURP结构域蛋白，油脂蛋白，半胱氨酸蛋白酶抑制剂及胚胎晚期丰富蛋白等基因。四个阶段中连续下调表达的基因包括胚胎晚期丰富蛋白，油脂蛋白及可能蛋白质磷酸酶2C等。4)将蛋白组与转录组进行关联分析，发现关联下调蛋白主要富集在应激反应，防御反应，金属离子反应，碳水化合物代谢等过程。通过与无叶假木贼幼苗在低温下的差异蛋白进行对比，发现16个低温差异蛋白在不同萌发阶段中差异表达。