First record of nucleus migration in premeiotic antherial cells of Saccharum spontaneum L. (Poaceae)

Abstract

The occurrence of nucleus migration is reported for the first time in a clone (2n = 64) of ‘Thatch’ grass (Saccharum spontaneum L.) of the family Poaceae. Usually, its premeiotic antherial cells are thin walled, uninucleate and without any trace of chromosome individuality. However, the cells of those anthers that had been affected from flood water stress conditions were anucleated to hexanucleated in varying frequencies. Out of 2567 cells analyzed, two and three cells were noticed to be connected to each other through a well-defined cytoplasmic channel. The nuclei were observed at various stages of their migration in interconnected cells. The remaining cells exhibited a mosaic of anucleate to hexanucleate cells in varying frequencies with a dominance of binucleated condition (43.75%). The anucleate ‘ghost’ cells were much smaller in size than the uninucleate, binucleate and multinucleate cells showing insignificant variation among themselves. The anucleate, binucleate and multinucleate cells appeared to be resulted due to nucleus migration through cytoplasmic channels between two cells. The presence of a nucleus in donor cell united with recipient cell having four nuclei of different sizes, diminutive anucleate cell in the neighbourhood of uninucleate/trinucleate cell or connected with cytoplasmic channel/pentanucleate cell, and disorganizing cytoplasmic channel attached with binucleate/ tetranucleate cell witnessed the accomplishment of nucleus migration. This rare phenomenon of nucleus migration seemed to be triggered by flood water induced stress and facilitated by feeble cell wall. The variation in sizes of nuclei in multinucleate cells might be due to the transfer of nucleus/nuclei of different size(s).  The prominent features of nucleus migration distinguishing it from the cytomixis have been discussed in detail. The syncytes resulted due to nucleus migration might have generated the pollen grains with different genetic constitution resulting into the origin of new intraspecific aneuploids/ polyploids for better adaptability.