叉孢苏铁茎的解剖学研究

Study on anatomy of the stem of Cycas segmentifida

关键词:  叉孢苏铁  茎  解剖结构

Key words:  Cycas segmentifida  stem  anatomical structure

摘要:

对叉孢苏铁茎的解剖结构进行了仔细的研究,结果表明:叉孢苏铁茎具有发达的皮层,皮层及髓中具有黏液道,有外韧型和周韧型的维管束分布在皮层中,但主要以外韧型为主,在同一切面上能看到横、纵、斜3种不同走向的维管束,所有皮层维官束韧皮部组成成份比较单一。维管组织区由多个生长环组成,每个生长环都具有木质部、维管形成层和韧皮部组成,各生长环韧皮部所占比例均大于木质部,在具4生长环的下部茎的维管组织中,环与环之间间隔2～10层不等的薄壁细胞。从纵向变化上看,从上至下,维管组织区的厚度及生长环数逐渐递增,在同一组织中,含晶及含单宁物质的异细胞呈从无到有,从少到多的分布趋势。

Abstract:

The anatomical structure of stem of Cycas segmentifida were studied. The results show that stem of C.segmentifida possesses of abundant cortex and there are mucilage canals distribute in cortex and pith. Collateral vascular bundle and amphicribral vascular bundle also distribute in cortex,but the most one is collateral vascular bundle. Three kinds of different trends vascular bundle-horizontal,vertical and slanting can be seen in the identical section. Phloem component of all vascular bundle in cortex are singleness. The vascular tissue consists of some growth rings,every growth ring is composed of outer phloem,middle cambium and inner xylem; in every growth ring,the ratio of phloem is more than xylem in vascular tissue. There are four growth rings in vascular tissue of bottom stem and there are 2-10 layers parenchyma cells between the two growth rings. Viewing from vertical variation,the thickness and the number of rings of vascular tissue is increasing from top to bottom. In the same tissue,from top to bottom,distribution trend of crystalliferous parenchyma cells and tannin parenchyma cells are from absence to presence and from few to many.