木兰科6属27种植物的叶片比较解剖学研究

Comparative Anatomy on the Leaves of 27 Species of 6 Genera in Magnoliaceae

应用石蜡切片技术和光镜观测方法,对采自云南昆明树木园的木兰科6属27种植物的叶片进行了比较解剖学研究。结果表明:(1)木兰科植物的叶片均为异面叶,由表皮、叶肉、叶脉构成;叶肉组织分化为栅栏组织和海绵组织,均具有圆形或近圆形油细胞;叶脉维管束韧皮纤维排列连续或不连续,成环状或轮状。(2)叶片下表皮细胞是否为具明显乳突的细胞和主脉维管束韧皮纤维细胞排列是否连续可明确区分木兰亚科和鹅掌楸亚科。(3)叶片厚度、上表皮厚度、海绵组织厚度可以对秃木兰属和鹅掌楸属进行明确区分,栅栏组织厚度、栅海比、油细胞大小和分布密度等余下性状则在数值上均存在属间重叠现象,不宜作为属间分类性状。(4)基于最大值和最小值进行的聚类结果与传统分类结果吻合度较基于平均值的聚类结果大,最大值和最小值比平均值更能表征研究对象。总之,表皮、下皮、叶肉组织和油细胞等部分叶片解剖学特征在探讨木兰科科下等级如亚科、部分属和部分种的分类地位时具有一定价值。

A comparatively anatomic study on the leaves of 27 species of 6 genera in Magnoliaceae was carried out with a light microscopy （LM） and paraffin sectioning method. The results show that （ 1 ） all leaf blades in Magno- liaceae are bifacial type and are composed of epidermis, mesophyll, vein. The mesophyll tissues are differentiated into palisade tissue and spongy tissure, in which round or nearly round oil cells are often found. The bast fibres of vascular bundles in the main vein are arranged into a continuous or discontinuous ring or wheel shape. （2） Lirio- dendroideae can be clearly distinguished from Magnolioideae by its lower epidermic cells papillate and by its bast fi- bres of vascular tissue arranged into a discontinuous ring or wheel shape. （ 3 ） Pachylarnax and Liriodendron can be recognized by the thickness of leaf blades, upper epidermis and spongy tissues. Numerically, the thickness of palisade tissues, the radios of the thickness of palisade tissues to that of sponge tissues and the size and the distribution density of oil cells overlap each other among the genera respectively and can not be used as intergeneric taxo- nomic characters. （4） The cluster result based on minimum and maximum values is better to match the traditional classification result than that on average values. The former two values characterize the research objectives better than the last one does. In short, some leaf anatomical characters such as epidermis, hypodermis, mesophyll tissue and oil cell can provide helpful information for discussing the taxonomic positions of the subfamilies, some genera and many species in the family Magnoliaceae.