披碱草属3组植物叶片解剖特征及其系统关系

采用石蜡切片法对披碱草属中小颖组、宽颖组和长颖组主要代表种的叶片横切面形态学特征进行观察。结果显示:(1)披碱草属3个组植物的叶片均为等面叶,由表皮、叶肉和维管束三部分构成,表现为典型的狐茅型,即表皮细胞形状、大小和排列不均,叶肉无栅栏组织和海绵组织之分,具有双层维管束鞘,周围叶肉细胞呈不规则排列,厚壁组织与表皮相接;但3个组植物在上表皮细胞形状、大小、沟的深浅,以及大型导管数目等叶片横切面特征上存在明显差异。(2)根据3个组植物叶片横切面性状的演化趋势,对各组的演化关系和系统位置分析表明,小颖组最原始,宽颖组较进化,长颖组最高级;小颖组可能直接派生了较进化的宽颖组,并在宽颖组的基础上进而产生了最高级的长颖组;小颖组、宽颖组和长颖组的这一系统关系与利用外部形态特征所获得的演化趋势基本一致。

Biosystematic Relationships and Leaf Anatomical Characteristics of Three Sects' Plants in Elymus (Poaceae)

The transverse sections of leaf blades of the major species of sect.Elymus,sect.Turczaninovia and sect.Macrolepis in Elymus were examined.The results showed that:(1)The leaf blade consists of epidermis,mesophyll and vascular bundle,which is isobilateral leaf.It belongs to the typical festucoid type.Namely,shape,magnitude and arrangement of epidermises are asymmetric.The mesophyll is not distinguished into palisade tissue and spongy tissue.They have double layer bundle sheath.The ambient mesophyll cells arranged irregularly and sclerenchyma is joined to epidermis.There are also obvious differences existing on the transverse section characteristics of leaf blades including shape,magnitude and depth of furrows in upper epidermises,number of large vessels,etc.(2)According to the evolutionary trends of transverse section characteristics of three sects,their evolutionary positions and relationships were inferred.The results show that the sect.Elymus is the most primitive one among the three sects,the sect.Turczaninovia is slightly more advanced than the former,and the sect.Macrolepis is the most advanced of them.The sect.Elymus might produce immediately the sect.Turczaninovia,whereas the sect.Macrolepis might derive immediately form the sect.Turczaninovia.The biosystematic relationships of these three sects are corroborated by the evolutionary trend of external morphology.