J Integr Plant Biol. ›› 1975, Vol. 17 ›› Issue (1): -.

• Research Articles •    

Light and Electron Microscopical Observations on Cytomixis and the Study of its Relation to Variation and Evolution

Cheng Kuo-chang, Nieh Hsiu-wan, Yang Chin-lan, Wang I-hsiu, Chou Ing-shou and Chen Jy-shi   

Abstract: Cytomixis has been studied with the light microscope using species of Lilium davidii var. willmottiae, Lycium chinense, Allium fistulosum and Allium cepa and electron microscope using Lilium davidii var. willmottiae. With the electron microscope, the cytoplasm and chromatin of a Lilium pollen-mother-cell (PMC)was observed passing into a neighbouring cell through several adjacent plasma channels. Cytomixis appears to be a natural phenomenon occurring either in the resting stage or meiosis between PMCs and other types of cells with thin or thick walls that are connected by cytoplasmic bands. Five different types of cytological abnormalities have been described also: 1. PMCs with decreased and increased chromosome numbers, 2. changes in chromosome structure, 3. appearance of enucleate and binucleate PMCs, 4. Registered bigger and smaller than normal pollen grains, and 5. detected unviable pollen grains. These types of abnormalities could be the result of cytomixis. Probably cells that are enucleate or have great disturbances in chromosome numbers and structure will die, while those with minor losses may survive. They may produce viable gametes or zygotes. In a very low frequency they may be expected to effect fertilization and thus give rise to aneuploid and polyploid progeny in a population. Cytomixis could be one of the modes of origin of B chromosomes by fragmentation of A chromosomes. Considering the above observations it may be thought that cytomixis in microsporogenesis and pollen development in many genera and families of flowering plants will increase our understanding of evolutionary mechanisms at cytological level.

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