CYTOMIXIS IN POLLEN MOTHER CELLS OF <i>ONONIS</i> (LEGUMINOSAE)

Abstract

Cytomixis occurred regularly in pollen mother cells (PMCs) of Ononis spinosa L., O. repens L. and O. arvensis L., from early meiotic prophase to telophase II. Usually only a few PMCs were affected in any anther, but occasionally whole anthers showed cytomictic patterns. Cytomixis generally was found at extremities but rarely in the median parts of anthers. Since it appeared to lead to the degeneration of affected PMCs or young microspores, it, therefore, could not give rise to aneuploidy. Cytomixis is interpreted as a pathological abnormality induced by pressure building up within the developing flower bud; it occurred where anthers pressed strongly against each other due to competition for space. It is suggested that uncoordinated growth rates of anthers and floral envelopes could account for intense cytomixis described in hybrids by various authors.