Cytomixis in monoploids
--P. Gayen and K.R. Sarkar

Cytomixis is no longer a fixational artifact (Basaviah and Murty, Cytologia 52:69-74, 1987). This phenomenon has been reported mainly in pollen mother cells of chromosomally imbalanced plants in a number of crop species (Nettancourt and Grant, Cytologia 29:191-195, 1964). In maize, cytomixis was reported in pollen mother cells of a triploid and its hyperploid progeny (McClintock, Genetics 16:175, 1929) and in a trisomic for chromosome 5 (Premchandran et al., Curr. Sci. 57:681-682, 1988).

We observed extensive cytomixis in two haploid plants, with 83% and 51% cells being involved in cytoplasmic connections and chromatin transfer. These plants were earlier treated with 0.06% colchicine at seedling stage (6-7 day old) by the cotton wad method, but doubling of chromosome number did not occur. Cell clusters having two to six cells were more common. The highest number of cells involved in a cluster was 48. In large clusters, cells with no chromosome (Æ) to as many as 27 chromosomes (Þ) were found to be present (Fig. 1). The number of cell-to-cell cytoplasmic connections ranged from one to four. In some cases a single cell was seen to be connected with five to six nearby cells (see figure).

Fig. 1. Part of a large cluster showing: cell with no chromosome (Æ), cell with 27 chromosomes (Þ) and multiple cytoplasmic connections.

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