夏侧金盏花幼苗初生维管系统的解剖学研究

ANATOMICAL STUDIES ON THE PRIMARY VASCULAR SYSTEM OF THE SEEDLING OF ADONIS AESTIVALIS L.

夏侧金盏花(Adonis estivalis L.)为毛莨科(Ranuncula-ceae)侧金盏花属(Adonis)植物。其幼苗可明显地分为上胚轴苗区、子叶节区和下胚轴根区。幼苗以子叶节区为中心,往上其子叶节区中部和上部为子叶节—茎过渡区;向下其下胚轴为子叶节—根过渡区。目前对毛莨科某些属幼苗初生维管系统的个体发育研究已有一些报道。但夏侧金盏花幼苗的子叶节—茎过渡区的转变与已报道的其他属均不同。主要表现为其子叶节区下部的中始式二原型双肩状单中柱,到达子叶节区中部,其后生木质部弦向发育成二唇形外韧维管束雏型,在中柱中央出现薄壁组织,进一步发育则形成髓;再往上,即子叶节区上部,便一分为多个内始式的外韧维管束雏型,直接形成上胚轴(茎)的真中柱。此研究为再一次验证子叶节区理论的正确性与进一步揭示被子植物初生维管系统的演化规律积累一份新资料。

Adonis aestivalis belongs to Adonis of Ranunculaceae. Its seedling isapparently divided into three zones: epicotyl shoot zone, cotyledon nodezone (CNZ) and hypocotyl root zone. The seedling is with the center ofthe cotyledon-node-zone, the middle and upper parts of the CNZ upwardare cotyledon-node-stem transitional region and the hypocotyl of theseedling downward is cotyledon-node root transitional region. Some onto-genetic studies on the primary vascular system of seedlings of somegenera in Ranunculaceae have been reported. But the transformation of thecotyledon-node-stem transitional region of A. aestivalis is different fromthose of other genera in Ranunculaceae. The main difference is that itsmetaxylem develops tangentially to form undeveloped double-lip-likecollateral vascular bundles after the mesarch, diarch haplostele withdouble fan-like metaxylem reaches the middle part of the CNZ. Theparenchyma appears in the center of the haplostele and divelops furtherto form the pith. The upper part of the CNZ is divided into severalundeveloped endarch collateral vascular bundles which directly formeustele of the epicotyl. This study is to testify the CNZ theory and revealthe evolutional rules of primary vascular system in Angiosperms.