| Summary: | 碩士 === 國立成功大學 === 生命科學系碩博士班 === 96 === Economically grasses are the most important plant family, in addition, they are the widely distributed group of vascular plants and have an extraordinary range of adaptation. In the grass family (Poaceae), the genus Digitaria are numerous and widely distributed in Taiwan. Fifteen taxa including fourteen species and two varieties are recognized, and are a difficult taxonomic group. The caryopsis morphology and seedling leaf anatomy of these taxa were studied by microscopy, and these data were entered as a DELTA database and then the cluster analysis was conducted by UPGMA and PCO. In general, the caryopsis are oblong-ovate, and the embryo are longer then 1/3 length of the caryopsis. Meanwhile, the punctuate hilium are 1/10~2/10 length of the caryopsis. There are some differences in the length of caryopsis and the ratios of length to width of the caryopsis. Their first leaves are horizontal or ascendant, and the shapes are various (oblong, oblong-lanceolate, lanceolate). The ratios of length to width of the first leaf are usually smaller than 7. The characters of leaf cross section are basically the same. However, there are some differences in the leaf lower epidermis especially the length of long cells, stomata, and macrohairs, etc. when measured.The results show the caryopsis morphology and seedling leaf anatomy characters are useful for species identification in the genus Digitaria in Taiwan. A key to species of the genus Digitaria in Taiwan is made based on the characteristics of caryopsis morphology and seedling leaf anatomy.
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