Unitat de Biologia Vegetal, Departament de Ciències Ambientals, Universitat de Girona, Campus de Montilivi s/n 17071 Girona, Spain;
Am J Bot. 2002 Mar;89(3):383-92. doi: 10.3732/ajb.89.3.383.
Anatomical changes at the cotyledonary node from the embryo to the seedling stage in Quercus coccifera, Q. ilex, and Q. humilis were investigated by light and scanning electron microscopy techniques. Mature embryos of Q. humilis possess 2-3 pairs of leaf primordia and a pair of cotyledonary buds, whereas in Q. coccifera and Q. ilex there are two incipient primordia, and cotyledonary buds are not observed until 1 wk after germination. In all three species the cotyledonary buds multiply, forming bud clusters, and a vascular connection is well established within 5-6 wk after germination. As development proceeds, the cotyledonary region becomes woody, but buds, which are exogenous in origin, never become embedded in the periderm. In comparison with Q. suber, another native Mediterranean Basin oak, the cotyledonary node is short and axillary buds are not present below the insertion of cotyledons. In addition, starch accumulation in the cotyledonary region is not observed from histological analysis in the three oaks. Therefore, in Q. coccifera, Q. ilex, and Q. humilis seedlings the cotyledonary node can be considered to be an important regenerative structure enabling them to resprout after the elimination of the shoot above the cotyledons, despite the absence of a lignotuberous structure.
采用光镜和扫描电镜技术研究了栓皮栎、欧洲栓皮栎和矮生栓皮栎从胚胎到幼苗阶段子叶节的解剖结构变化。成熟的矮生栓皮栎胚胎具有 2-3 对叶原基和一对子叶芽，而在栓皮栎和欧洲栓皮栎中则有两个初始原基，直到发芽后 1 周才观察到子叶芽。在这三个物种中，子叶芽增殖，形成芽簇，并且在发芽后 5-6 周内建立了良好的血管连接。随着发育的进行，子叶区域变得木质化，但起源于外生的芽永远不会嵌入周皮中。与另一种原产于地中海盆地的栓皮栎（Quercus suber）相比，子叶节点较短，子叶插入处下方没有腋芽。此外，从这三个栎属植物的组织学分析中没有观察到子叶区域的淀粉积累。因此，在栓皮栎、欧洲栓皮栎和矮生栓皮栎幼苗中，尽管没有木质块茎结构，但可以认为子叶节点是一种重要的再生结构，使它们能够在子叶上方的枝条被去除后重新萌发。
