University of Quebec in Abitibi-Témiscamingue, 445 boulevard de l'Université, Rouyn-Noranda, Quebec, J9X 5E4, Canada.
Am J Bot. 2009 Aug;96(8):1500-5. doi: 10.3732/ajb.0800177. Epub 2009 Jul 20.
Trembling aspen (Populus tremuloides) is a clonal tree species, which regenerates mostly through root suckering. In spite of vegetative propagation, aspen maintains high levels of clonal diversity. We hypothesized that the maintenance of clonal diversity in this species can be facilitated by integrating different clones through natural root grafts into aspen's communal root system. To verify this hypothesis, we analyzed root systems of three pure aspen stands where clones had been delineated with the help of molecular markers. Grafting between roots was frequent regardless of their genotypes. Root system excavations revealed that many roots were still living below trees that had been dead for several years. Some of these roots had no root connections other than grafts to living ramets of different clones. The uncovered root systems did not include any unique genotypes that would not occur among stems. Nevertheless, acquiring roots of dead trees helps to maintain extensive root systems, which increases the chances of clone survival. Substantial interconnectivity within clones as well as between clones via interclonal grafts results in formation of large genetically diverse physiological units. Such a clonal structure can significantly affect interpretations of diverse ecophysiological processes in forests of trembling aspen.
颤杨（Populus tremuloides）是一种克隆树种，主要通过根蘖进行再生。尽管进行了营养繁殖，颤杨仍保持着高水平的克隆多样性。我们假设，通过天然根嫁接将不同克隆整合到颤杨的公共根系中，可以促进该物种克隆多样性的维持。为了验证这一假设，我们分析了三个纯颤杨林的根系，这些林分中的克隆是借助分子标记来划分的。无论其基因型如何，根之间的嫁接都很频繁。根系挖掘表明，许多根系仍然存在于已经死亡数年的树木下方。其中一些根除了与不同克隆的活嫩枝嫁接外，没有其他根连接。未被发现的根系不包括任何除了茎干之外不会出现的独特基因型。然而，获得死树的根系有助于维持广泛的根系，从而增加克隆存活的机会。克隆内以及通过克隆间的嫁接大量的互连导致形成大的遗传多样化的生理单位。这种克隆结构会显著影响对颤杨森林中各种生态生理过程的解释。
