Some observations on the reproduction of tridax procumbens L

Abstract

Chromosome data place Tridax procumbens at the tetraploid level. Regularity of bivalent formation suggests that little homology exists between the constituent genomes but meiotic irregularities nevertheless occur frequently and result in some 15% of the pollen being obviously non-viable. Premeiotic aberrations in the walling of the sporogenous tissue give rise to ‘normal’ and ‘giant’ pollen mother cells. The latter are characterised by their abnormal size and often by their massive walls and elongated “tails” of either walled cytoplasm or wall material alone. The largest giant cells are binucleate. Meiotic irregularities in the ‘normal’ pollen mother cells include the formation of a quadrivalent or a trivalent and univalent; one or more lagging bivalents; first and second division bridges and the failure of spindle formation at either the first or second divisions. In the ‘giant’ cells delay in the onset of meiosis occurs frequently, cells showing prophase or diakinesis being found among tetrads or differentiating pollen grains. Other giant cells show highly irregular divisions culminating in a variable number of nuclei. An attempt at cleavage into microspores occurs in a minority of these cells. The nuclei in binucleate giant cells do not necessarily behave synchronously and, as in the uninucleate giant cells, often show delayed or arrested division. In the minority, where both nuclei negotiate the division successfully a “tetrad” of eight apparently normal microspores may result. While the cause of the initial irregular cytoplasmic cleavage remains unknown, it is tentatively suggested that the subsequent meiotic retardation and irregular division in the giant cells may be related to their abnormally high cytoplasmic/nuclear volume. © 1969, Japan Mendel Society, International Society of Cytology. All rights reserved.