穇属颖果微形态及其系统学意义

Caryopsis Micromorphology of Eleusine Gaertn. (Poaceae) and Its Systematic Implications

在电子扫描显微镜下观察了穇属(Eleusine Gaertn.)9种植物颖果的微形态特征。结果表明,穇属颖果有卵形、披针形和矩圆形3种腹面形状,压扁方式有背腹压扁及两侧压扁,腹面形态有平腹面和凹腹面两种,胚比为0.29～0.58,种脐比为0.10～0.24,颖果纹饰有2种,包括疣突状一级纹饰和疣突规则排列构成的复合网状(二级)纹饰,表面小孔平均直径0.57～1.31μm,分布密度为30～200个(100μm-2)。穇属植物的颖果腹面形状、纹饰、表面小孔直径及平均密度等性状,可为种类鉴定及种间关系分析提供有价值的证据。穇属颖果腹面形态呈平腹面或凹腹面,颖果体积相对小,生活周期相对缩短,这可能是与东非季节性干旱气候相适应的。

Caryopsis micromorphological characteristics of nine species of Eleusine were studied using the scanning electron microscopy （SEM）. The results showed that there were three types of ventral shapes in caryopses including oval, lanceolate, and oblong, two types of compression including dorsiventral and lateral, two types of ventral faces including flat and concave. The embryo proportion ranged from 0.29 to 0.58, and hilum proportion from 0.10 to 0.24. There were two types of surface sculpture including the verrucate simple sculpture and the compound reticulate sculpture composed by the regular spread of verrucae. The mean diameter of caryopsis foveola ranged from 0.57 μm to 1.31 μm with a density from 30 to 200 in 100 μm2. It can be concluded that caryopsis ventral shape, sculpture, and foveola are very useful characteristics for the identification of species and the inference of interspecific relationships in Eleusine. Because of the flat and concave ventral face, caryopses of Eleusine have relatively small bulk, therefore possibly aiding rapid development and maturation. All characters seem to be particularly valuable in climates of East Africa seasonal drought.