悬铃木幼苗的初生维管系统演化结构研究

Study on the evolutionary structure of primary vascular system in sycamore seedlings of Platanus acerifolia(Ait.)Willd

利用石蜡连续切片方法对悬铃木(Platanus acerifolia Willd.)幼苗初生维管系统进行了研究.结果表明:二球悬铃木具有较长的子叶节区,几乎占幼苗下胚轴的全部;根端为外始式二原型(或真二原假四原)辐射中柱;子叶节区下部的结构较原始,具有中始式二原型单中柱;中部出现具髓的中始式二原型管状中柱阶段;上部与茎的内始式真中柱极为相似且较短,所以只存在子叶节区茎结构连接区;上胚轴的苗区具有内始式真中柱;由于二球悬铃木幼苗子叶节区结构具有中始式二原型单中柱,子叶为二叶迹;而胚芽起源的营养叶为三叶迹;幼苗子叶节区类型属于顶枝伸长型,结构原始.

The primary vascular system of Platanus occidentalis L.seedlings was studied by paraffin serial section.The results showed that sycamore tree had a long cotyledon node zone(CNZ)segment,which accounted for almost all the hypocotyl of the seedlings.The root tip is a radiating middle column of diarch(true diarch,or tetarch)radiation cylinder.The structure of the lower part of cotyledon node zone CNZ is primitive,with a single cylinder of the diarch.A medullated mesotypic binary prototype tubular mesocolumn stage appears in the middle.The upper part of the stem is very similar to the inner primordium of the stem and is shorter,so only the stem structure connection region exists in the cotyledon node zone CNZ.The seedling area of the epicotyl has an inner beginning true stele.Because the structure of cotyledon node zone CNZ of sycamore seedlings has a single middle cylinder of diarch.The cotyledon node zone CNZ cotyledon is a two-leaf trace.The vegetative leaf of germ origin is trifoliate trace.The experimental results fully demonstrated the primitiveness of the cotyledon node zone CNZ of seedlings.