Evaluation of mitotic activity in tapetal cells of grapevine (Vitis L.)

Abstract

The knowledge with reference to the grapevine tapetum has been centered on its anatomy/morphology and hardly anything at all is known about its mitotic activity throughout the microsporogenesis. The aim of this study was to ascertain the mitotic activity in tapetal cells of some grapevines (Vitis L.) broadening knowledge about this tissue and simultaneously corroborating the viability of its use as an alternative tissue for further cytogenetic studies. Young buds of 12 grapevine varieties at different meiotic stages were squashed and tapetal cells a prometaphase/metaphase scored in each meiotic stage. Mitotic activity was observed since the beginning of microsporogenesis, where it was more intense, decreasing toward tetrad. Polyploid tapetal cells arose through endomitosis while the microsporogenesis advanced. Two types of polyploid cells were evidenced, those with two or more individualized diploid chromosome groups and those with only one polyploid group. The percentage of diploid cells and of polyploid cells with two or more individualized diploid groups was higher during the first stage of microsporogenesis, though decreasing and giving way to cells with one large polyploid group as microsporogenesis moved toward tetrad. The nucleolus number was scored at interphase at different stages. Two and four nucleoli prevailed in tapetal cells at all stages except at tetrad where one large nucleolus was seen. The results showed that despite of the squashing technique applied, grapevine tapetum has a substantial amount of cells with mitotic activity with a satisfactory chromosome spreading therefore establishing an interesting alternative and promising tissue for later cytomolecular studies.