贵州小檗属植物(小檗科)叶脉序研究

Leaf venation of Berberis(Berberidaceae)in Guizhou

关键词:  小檗科  小檗属  叶脉序  分类学  贵州

Key words:  Berberidaceae  Berberis  leaf venation  taxonomy  Guizhou

摘要:

采用制作叶脉标本和透明叶标本的方法,对贵州产28种2变种小檗属植物叶脉特征进行比较研究。结果表明:贵州小檗属植物的脉序类型有5种:半达缘羽状脉、花环状半达缘羽状脉、简单弓形羽状脉、花环状弓形羽状脉和混合型。叶脉分支一般有五级:①一级脉构架均为羽状脉,粗度有很粗、粗、中等粗细和纤细四种类型,分支方式包括单轴分支和合轴分支; ②粗二级脉构架中有分支达缘或分支均不达缘,与中脉夹角变化各异,内二级脉存在或缺失,细二级脉半达缘、真曲行或简单弓形,间二级脉类型复杂多变但频度种间有差异; ③三级脉贯串型、结网型或分支型; ④四、五级脉网状或自由分支且常混合在一起。脉间区从发育差到良好,小脉从不分支到不均等分支等各种类型均有,叶缘末级脉缺失、不完整、钉状和环状。大部分种类叶缘具齿,每1 cm齿数目和齿内腺点的特性等特征在不同种类间有区别,具有鉴定价值,但齿其它特征复杂多变或种间区别较小,同时齿内脉性状也不稳定。此外,齿的有无会对脉序类型产生影响。小檗属植物叶脉类型存在种间差异,具有重要的分类学价值,叶脉类型的变化和复杂程度显示了该属植物的进化特点; 叶齿的有无和齿特征具有分类学和系统学意义。基于叶脉特征的研究结果并结合重要的外部形态学特征编制了贵州小檗属植物的分种检索表。研究结果可为小檗属植物分类寻找新的依据并探讨其系统学意义。

Abstract:

Leaf venation of 28 species and 2 variety species of Berberis(Berberidaceae)in Guizhou were made a comparative observation to search new taxonomic evidences and make a study of its systematic significance in Berberis by the means of making leaf venation specimens and clearing leaf specimens. The results showed that venation pattern could be divided into five types: semicraspedodromous, festooned semicraspedodromous, simple brochidodromous, festooned brochidodromous and the mixed. The highest vein order is fifth-order course. Primary veins framework were all pinnate and had a single first-order vein, the size included massive, stout, moderate and weak four types and the branching ways include monopodial and sympodial. Major secondary vein framework include two types: one type was that major secondaries branch to the margin, one of the branches terminates at the margin, and the others joined the superjacent major secondary or formed more than one set of loops; the other was that major secondaries joined in a series of prominent arches and loops of secondary gauge or branched into multiple sets of loops of secondary gauge, often with accessory loops of higher gauge and all the major secondaries did not reach the margin, variation of major secondaries angle to midvein separately. Interior secondaries present or absent, formed loops of secondary gauge or branched to the base of the leaf and midvein if present; minor secondary course included semicraspedodromous, simple brochidodromous and eucamptodromous; intersecondary veins were complicated, but the average number of intersecondry veins per intercostal area were different among the species. Tertiary veins crossed between adjacent secondaries, anastomose with other tertiary veins and secondary veins to form a net or branch without forming a tertiary reticulum. Quaternary and quinternary veins were formed by fourth-order vein and fifth-order vein courses, and always mixed, they anastomosed with other veins to form a net or branch freely and to be the finest vein-order the leaf exhibits, besides, they were also components of freely ending veinlets. The present of the areolation was from poor development to good development. Freely ending veinlets changed from unbranched to branch unequal. Marginal ultimate venations included the absent, incomplete, spiked and looped. Most species had leaf teeth along the margin, number of teeth per centimeter and gland characters in the tooth are different among the species, and had identification values, but other tooth characters such as tooth spacing and shape were complicated and changeful or had little differences among the species, at the same time, venation in the teeth were unstable, too. Besides, leaf teeth had an effect on the leaf venation pattern. Different kinds of leaf venation patterns presented among the species and had a important significance in taxonomy, variations of leaf venation patterns and complicated degrees showed the evolvement characters of the Berberis; present of the leaf teeth and its characters also had certain significance in taxonomy and systematology. Main leaf venation characters of the species were summarized in a table for the species of Berberis in Guizhou, based on the leaf venation characters with main diagnostic morphologically.