大麦亚族3属植物的叶片解剖特征及其系统关系

Biosystematic Relationships and Leaf Anatomical Characteristics of Plants of Three Genera in Hordeinae(Poaceae)

采用石蜡切片法对大麦亚族中新麦草属、芒麦草属和三柄麦属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)大麦亚族3属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,即下表皮细胞形状、大小和排列均匀,上表皮细胞形状、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属植物在上表皮的凹凸程度,下表皮细胞壁的厚薄,叶肉组织中部束间厚,大小型维管束的数目、中肋维管束横径等叶片横切面特征上存在明显差异。(2)根据3属植物叶片横切面性状的演化趋势,对各属的演化关系和系统位置分析表明,新麦草属最原始,芒麦草属较进化,三柄麦属最高级;新麦草属可能直接派生了较进化的芒麦草属,并在芒麦草属的基础上进而产生了最高级的三柄麦属;新麦草属、芒麦草属和三柄麦属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。

The transverse sections of leaf blades of the major species of Psathyrostachys, Critesion and Hordelymus in Hordeinae were examined. The result shows： （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 lower epidermises are symmetrical, while those of upper 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 selerenchyma is joined to epidermis. There are also obvious differences existing on the transverse section characteristics of leaf blades including protuberant extent of upper epidermises, thickness of cell -walls in lower epidermises, thickness between the strands in middle part of mesophyll, number of vascular bundles, midrib diameter in horizontal, etc. （2） According to the evolutionary trends of transverse section characteristics of three genera, their evolutionary positions and relationships were inferred. The results show that Psathyrostachys is the most primitive one among these three genera, Critesion is slightly more advanced than the former, and Hordelymus is the most advanced of them; Psathyrostachys might produce immediately Critesion, whereas Hordelymus might derive immediately form Critesion. The biosystematic relationships of these three genera are corroborated by the evolutionarv trend of external momholo.