中国珍稀濒危植物东方水韭二歧根的发育

Dichotomous Root Development in Isoetes orientalis,a Rare and Endangered Quillwort in China

用石蜡切片的方法首次揭示了中国特有水生蕨类植物东方水韭根的生成与二歧根的发育,解剖学结构显示水韭属植物成熟根主要由表皮、外皮层、连接细胞、中央维管束和通气组织5部分组成;东方水韭二歧根的形成过程中,幼根顶端分生组织中央的3个细胞成为二歧根发育的原始细胞,原始细胞进一步分化形成内原始细胞和外原始细胞,分化后的外原始细胞组成的活跃中心将各自成为新的二歧根的原始细胞,使二歧分叉的根形成一个倒“Y”字形结构;根冠紧邻外原始细胞的末端;水韭不同种根内中央维管束的管胞数目存在差异.本研究对水韭属植物个体发育具有借鉴意义.

In this paper, root morphogensis, root anatomy, and the branching pattern of young roots in Isoetes orientalis, a Chinese endemic aquatic fern, were investigated from sections in paraffin wax. The mature root in Isoetes is composed of epidermis, outer cortex, connective cells, central vascular tissue, and aerenchyma. Prior to branching, three primordial cells at centre of the apical meristem of the young root of I. orientalis differentiate into root initial cells. The root initial cells further differentiate equally into outer and inner initial cells. The outer initial cells constitute the central core of each new branching root and subsequently formed an inverted ＂Y＂ shaped structure in the root. The root cap occurs immediately beneath the outer initial cells. The number of tracheids in vascular tissues of the root varies considerably among different species of Isoetes. This study means significant to the ontogeny of Isoetes.