燕麦属颖果微形态特征及其分类学意义

Caryopsis Micromorphological Charateristics of Avena(Poaceae) and Its Taxonomic Significances

为探讨燕麦属颖果微形态特征的分类学意义,采用体视显微镜和扫描电子显微镜观察燕麦属27种颖果的微形态特征,结合分子系统发育证据分析其分类学意义。燕麦属颖果有纺锤形、倒披针形、椭圆形3种形状,条纹、棱纹、网纹3种纹饰。燕麦属颖果形状、纹饰和花柱基宿存模式具有有限的属下分类学意义,颖果大小和表面大毛密度具有种间鉴定价值,而颖果腹面形态、压扁方式、胚比不具有种间鉴定价值。大穗燕麦(Avena macrostachya Balansa ex Coss.&Durieu)颖果纺锤形,条纹纹饰,隶属于燕麦属颖果微形态特征的变异范围。大粒裸燕麦(A.nuda L.)与普通栽培燕麦(A.sativa L.)颖果大小、形状及纹饰特征的差异支持将大粒裸燕麦作为独立种处理。燕麦属颖果大小、表面大毛密度、胚比变异幅度大,推测与分布区广幅的气候变异相适应,凹腹面颖果体积相对缩减,有利于颖果快速发育、成熟,推测与燕麦属植物在温带、寒带分布区适生期较短相适应。

In order to understand the taxonomic significance of caryopsis characters in Avena L.(Poaceae), the micromorphology of 27 species caryopsis were observed under stereoscopic microscopy and scanning electron microscopy, and its taxonomic significances were analyzed combining with molecular phylogenetic reconstruction. The results showed that there were three shapes of caryopses in Avena, including fusiform, oblanceolate and elliptic, and three spermoderm sculpturing patterns, including striate, ribbed and reticulate. Caryopsis shapes, spermoderm sculpturing patterns and stylopodium persistence patterns showed limited taxonomic significance at the infrageneric level, and caryopsis size and macrohair density were of important diagnostic characters at the interspecific level, while caryopsis ventral face, compression, and embryo proportion had limited diagnostic significance at the interspecific level in Avena. Avena macrostachya Balansa ex Coss. & Durieu should be treated as a member of Avena due to its caryopsis characters of fusiform and striate sculpturing pattern falling within the variation scope of caryopsis micromorphological characters of Avena. The differences of caryopsis size, shapes,spermoderm sculpturing patterns between A. nuda L. and A. sativa L. supported that A. nuda should be treated as a separate species. The wide variation ranges of caryopsis size, macrohair density and embryo proportion indicated that they were the adaptive consequences of wide variation range of climate condition across the geographical distribution region of Avena. The caryopses of concave ventral face have a relatively small bulk, which may have aided rapid development and maturation, a rhythm that is of particular value in short growth period in temperate and cold distribution region for Avena.