| Abstract: | This paper deals with the comportmem of the vegetative nucleus and its spatial association with the generative cell and sperm cells in the artificially germinated pollen tubes of Zephyranthes candida (Lindl.) Herb. before and after generative cell mitosis with the use of DNA-specific fluochrome 4′,6-diamidino-2-phenylindole (DAPI). The induction of amitosis and abnormal mitosis of generative cell nuclei by cold-pretreatment of the pollen prior to germination was studied in particular. In normal case, the generative cell, after appressing to the vegetative nucleus for certain time, underwent mitosis to form two sperms, while the vegetative nucleus became markedly elongated, diffused, and exhibited blurring of its fluorescence. After division, a pair of sperms remained shortly in close connexion with the vegetative nucleus. Then the vegetative nucleus returned to its original state. In the pollen tubes germinated from cold-pretreated pollen, amitosis of some generative cell nuclei were frequently observed. Amitosis took place via either equal or unequal division with a mode of constriction. During amitosis, the dynamic change of vegetative nucleus and its intimate association with generative cell afore described did not occur. Sperm nuclei produced from amitosis could farther undergo amitisis resulting in micronnclei. Factors affecting the amitosic rate of generative cells, such as pollen developmental stage, temperature and duration of cold-pretreatment, were studied. Besides amitosis, cold-pretreatment also induced some abnormal mitotic behavior leading to the formation of micronuclei. Based on our observations and previously reported facts in other plant materials, it is inferred that the vegetative nucleus plays an important role in normal mitosis of generative cell and development of sperms. |
