禾本科植物幼苗性状的聚类分析

本文用201种禾本科植物幼苗的60个形态和解剖性状进行了聚类分析，将禾本科植物分为四个大类(一级聚合单位)—狐茅类(Festucoid)、黍类(Panicoid)，竹类(Bambusoid)和画眉草类(Eragrostidoid)。这四类基本上与分类系统中的亚科相吻合，只是芦竹亚科植物的幼苗分散聚到了其它类中。推测芦竹亚科是一个比较原始的类群，狐茅亚科、黍亚科和画眉草亚科可能是在芦竹亚科的基础上进化而来的。  除个别种外，大多数同属的种在较低的聚合水平上聚在一起，超族在亚聚合单位中基本上能够反映出来。  研究证明禾本科植物的幼苗性状在禾本科植物分类中具有重要的分类学意义。

A Cluster Analysis of Seedling Characters of the Gramineae

Seeds of 201 species of 83 genera in the Gramineae were collected from the tropical and subtropical regions of Australia, and the temperate region of China. Pure live seeds of each species were sown in plastic pots, which were filled with the mixture of sand and bits of rotted wood (4:1). Seeded pots were kept in greenhouse at temperature of 20—25°C , and were arranged at random with four replications in each of the two treatments of sowing depth, 10 mm and 0 mm. The seedlings were taken as samples for examining 60 morphological and micro- scopic characters (Appendix), when they grew to the three-leaved stage. Cluster analysis was made using 60 seedling characters with the 201 species as OTUs. As a result, four clusters are recognized as follows.      Cluster 1. Festucoid: The group consisted of all the species of the subfamily Festucoideae, the species of the genera Stipa, Achnatherum, Danthonia and Aristida in the subfamily Arundinoideae, and those of the genus Microlaena  in the subfamily Bambusoideae. The seedling mesocotyl elongated or not, but not elon- gated when grew under light. Mesocotyl roots absent. Scutellum and coleorhiza node roots or coleoptile node roots dominant. The first leaf narrowly linear, erect, acute at the apex, twisting clockwise or counterclockwise;   blade and sheath  3—5-nerved, with the blade length/width ratio 61.65 on an average;  The se- cond and third leaves narrowly linear, acute or acuminate at the apex. The coleoptile 13.04mm long on an average. The first tiller appeared when the third leaf emerged.     Cluster 2. Panicoid: All the species of the subfamily Panicoideae, the species of the genera Eriachne and Monachather in the subfamily Arundinoideae, and the genus Enneapogon  in the subfamily Eragrostidoideae were included in this group. The seedling mesocotyl elongated, even if growing under light. Mesocotyl roots present and dominant. Scutellum and coleorhiza node roots absent. The first leaf oblong-lanceolate, oblong-oblanceolate or spathulate, ascendent or horizontal, acuminate or obtuse at apex, not twisting;  blade and sheath over 7-nerved, with the blade length/width ratio 8.95 on an average. The second and third leaves linear-lanceolate, lanceolate or oblong-lanceolate, acuminate at the apex. Coleoptile 5.29mm long on an average. The first tiller appeared when the fifth leaf emerged.     Cluster 3.  Bambusoideae: This group included the species in the subfamily Bambusoideae except those in the genus Microlaena.  The first and second leaves without blade in the supertribe Bambusanae.  The mesocotyl not elongated. Scutellum and coleorhiza node roots, and coleoptile node roots completely absent, only primary root developed. The mesocotyl elongated, mesocotyl roots absent and coleoptile roots dominant in the supertribe Oryzanae. The blade of the first leaf suppresed, but the second and third leaves both with blade and sheath.      Cluster 4. Eragrostidoid: The cluster contained the species in the subfamily Eragrostidoideae except those in the genus Enneapogon. The seedling mesocotyl elongated, but not elongated when grew under light. The mesocotyl roots mostly absent, while the coleoptile node roots dominant. The first leaf linear, almost as- cendent, acute at the apex, not twisting, blade and sheath 5—7 (9)-nerved, with the blade length/width ratio 11.69 on an average. The second and third leaves linear,  linear-lanceolate  or lanceolate,  acuminate at the apex.  The coleoptile 2.60 mm long on an average. The first tiller appeared when the fifth leaf emerged.      The species of the subfamily Arundinoideae were divided into four clusters. The results showed that the Arundinoideae could be considered as primitive mem- ber of the family, from which the subfamilies Panicoideae, Eragrostidoideae and Festucoideae are derived and specialized.      With exception of a few cases, species in a genus were generally clustered into one unit and grouped into a subcluster unit.      Seedling  characters,  like  other  taxonomic  characters,  are  of importanttaxonomic significance, and could be used in classification of the Gramineae.