The Polytene Chromosomes of Anther Tapetum of Some Phaseolus Species.

Abstract

The chromatin organization of tapetal cells of some Phaseolus species was analysed with Giemsa staining. They presented endoreduplication cycles which may result in large endochromocentres or more or less condensed chromatid bundles, visualized as polytene chromosomes, properly. P. coccineus and P. vulgaris showed the best developed polytenics, whereas P. acutifolius, P. lunatus, P. microcarpus and P. peduncularis, showed endochromocentres eventually associated with small chromatid bundles. The tetraploid hybrid P. acutifolius×P. vulgaris showed tapetal nuclei with the characteristics of both parents. The ability to bundling the sister chromatids was intrinsic to each species and was similar to that previously reported in embryo suspensor cells. The polytene chromosome morphology and the change from dispersed state to a more condensed one suggest the occurrence of a coiling cycle which seemed to advance in the endoprophase more often and deeper in P. coccineus and P. vulgaris than in the remainder species.