Asyndesis and Meiotic Non-reduction in Microsporogenesis of Apomictic Paspalum secans

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Abstract
The materials of P. secans that have been studied represent several different pseudogamous, obligately apomictic clones of the species. The microspore meioses are characterized by a uniformly high degree of asyndesis and the usual occurrence of restitution nuclei. An upset in timing relations of the processes involved in division is suggested by wide variation in the time of initiation of meiosis among the microsporocytes in an anther, complex chromosome movements in many cells, and irregular cleavage of some cells at various stages of chromosome behavior. Restitution nuclei may be formed at any stage after diakinesis, with the stage at which they occur apparently having a general relationship to the time at which division was initiated in that cell relative to other microsporocytes in the anther. The initial movement of the univalents is toward the poles of the spindle, and is sometimes completed with the formation of telophase nuclei that remain distinct. In most microsporocytes, however, the movement toward the poles is followed by a movement of the chromosomes toward the equator. At a later stage which is found in some cells the univalents at the equator can be seen in process of division. This division may result in the splitting of many univalents, but soon afterward breaks down with the formation of a restitution nucleus. Although some irregularities were observed, the post-restitution division is usually regular and results in the formation of dyads of unreduced microspores.

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