粗糙龙胆根系发育形态学研究

为了解粗糙龙胆的根系特点，采用常规观察和石蜡切片法对粗糙龙胆根系的发育过程和1~4年生根的解剖结构进行研究。结果表明：1年生的实生苗多为直根系，2年以上植株发育为须根系，随着根龄的增加整个根系基本垂直向下或偏向一侧生长。不同根龄的不定根结构相似，由外至内包括表皮、皮层和次生维管组织。随着根龄的增加，表皮逐渐脱落完全，依靠外皮层和其内侧紧邻的外皮层母细胞代替表皮起到保护作用，内皮层宿存，至4龄根并未见明显周皮。维管形成层由2~5层扁平细胞构成；随着根龄的增加次生韧皮部和次生木质部的面积逐渐增大，韧皮薄壁细胞依然占主要部分，次生木质部不发达。在一些4年生根的髓部中央出现新结构即髓心内皮层。因此，粗糙龙胆根系的发育和解剖结构特点与其生长环境相适应，新结构髓心内皮层的发育过程和功能还需进一步研究。

Root Development of Gentiana scabra: Morphological Study

To understand the root characteristics of Gentiana scabra, we studied the developmental process and the anatomical structure of 1-4 year-old roots of G. scabra by using the routine observation and the paraffin methods. The results showed that: 1-year seedlings mostly belonged to tap root system, and more than 2-year plants developed into fibrous root system, the whole root system grew vertically downward or inclined to one side with the increase of root age; the structure of adventitious roots at different root ages was similar, consisting of epidermis, cortex and secondary vascular tissue from the outer to the inner; with the increase of root age, epidermis gradually shed completely, and the protective effect of the epidermis was replaced by its inner adjacent cortex and the mother cells of the outer cortex, its endodermis persisted, and no obvious periderm was seen at 4-year-old root; the vascular cambium composed of 2-5 layers of flat cells; the area of secondary phloem and secondary xylem increased step by step with the increase of root age, but the phloem parenchyma cells still accounted for the main part, secondary xylem was underdeveloped; a new structure appeared in the medullary center of some 4-year-old roots which was the pith endodermis. Therefore, the development and anatomical structure characteristics of roots of G. scabra are suitable for its growth environment, moreover, the development processes and functions of new structure which is the pith endodermis need to be further studied.