Embryological studies on Narcissus tazetta var. chinensis

Wu-Jian; Chen-Lin-Jiao; Gu-Li; Wang-Ya-Ying; Tian-Hui-Qiao

Xiamen Daxue Xuebao (Ziran Kexue Ban) 44(1): 112-117

2005


DOI: 10.1007/s11515-005-0007-2
Accession: 012033214

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Abstract
Chinese Narcissus has been a favorite ornamental plant in China for several hundred years. Since the plant blooms but has no seeds, it only reproduces by vegetative propagation. Embryological studies of Chinese Narcissus (Narcissus tazetta var. chinensis) were conducted to discovery the causes of sterility. The anther wall is composed of four layers and its tapetum is of the secretory type. The cytokinesis in microspores mother cells is of the successive type and the arrangement of the microspores in tetrad is tetrahedral. During meiosis of microspore mother cells, some chromosomes lag behind and several micronuclei are found in tetrads. After meiosis,as most microspores abort and cytoplasms decrease,only 27. 7% of pollen grains could develop with full cytoplasm. Among the normal pollen grains,only 1. 3% of them could germinate pollen tubes in culture medium. No pollen grain, however,could germinate on the stigma and no pollen tube was found in the style. The ovary is trilocular with axile placentation and the ovules are bitegminous, tenuinucellatae and anatropous. After meiosis of the megaspore mother cell, the chalazal megaspore develops into a polygonum type embryo sac. Most embryo sacs, however, degenerate during their development and only about 4. 5% of megaspore mother cells could produce normal embryo sacs, each of which has one egg cell, two synergids, three antipodal cells and a central cell containing two polar nuclei. Some of the abnormal embryo sacs were hollow and some of them had over four nuclei in the centre. One reason of the sterility of Chinese polyanthus is the abnormality of microsporogenesis and megasporogenesis,which lead to few functional pollen grains and embryo sacs developing. The other reason is that the pollen grains can not germinate on the stigma and no pollen tube could grow into the style.

Embryological studies on Narcissus tazetta var. chinensis