The Mechanism of Apomixis in Pennisetum ciliare

Asyndesis and Meiotic Non-reduction in Microsporogenesis of Apomictic <i>Paspalum secans</i>

“…The finding of these phenomena with associated low pollen fer tility has been reported, for example, by Muntzing (1928Muntzing ( , 1931 in several polyploid biotypes of Potentilla collina, and by Snyder et al (1955) in an euploid and tetraploid clones of Pennisetum ciliare.…”

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An earlier paper (Snyder 1957) was concerned with the occurrence of obligate apomixis in several clones of Paspalum secans Hitchc. and Chase collected in the vicinity of Mayaguez, Puerto Rico, the type locality of the species.

The clones investigated were found to be aposporic, with embryo development initiated by autonomous diploid parthenogenesis.

Normal develop ment of the embryos and the formation of caryopses, however, were found to depend on fertilization of the polar nuclei and subsequent endosperm forma tion, i.e., the clones studied are pseudogamous.

Meiotic behavior during megasporogenesis was not studied in detail, although large numbers of uni valent chromosomes were readily apparent at diakinesis and first metaphase.

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“…An earlier paper (Snyder 1957) was concerned with the occurrence of obligate apomixis in several clones of Paspalum secans Hitchc. and Chase collected in the vicinity of Mayaguez, Puerto Rico, the type locality of the species.…”

Apomixis inCortaderia jubata(Gramineae)

“…This explanation could apply to most grass apomicts, including C. jl/bata. However, in several apomictic grasses the egg remains undivided until after the pollen tube reaches the embryo sac, e.g., PanicIIIII rnaxillllll/l (Warmke 1954), PCllllisctll1ll ciliare (Snyder et al 1955), and Themeda triandra .…”

A Study of Cytological Variation in Chromosomal Races of Two Species of <i>Cenchrus</i>

“…In C. setigerus, only two chromosomal forms viz., 2n=36 and 54 have so far been isolated, whereas in C. ciliaris as many as ten viz., 2n=32, 34, 36, 38, 40, 42, 44, 52, 54 and 56 have been identified (Donald 1953, Darlington and Wylie 1955, Jogindernath and Swaminathan 1957, Patil et al 1961, Chandrasekharan 1961, Jagannath 1963, Ponnaiya et al 1966. The irregularities in chromosomal behaviour at meiosis and the variation in chromosome number resulting therefrom in the progenies are maintained in the population due to aposporous and facultative apomixis (Fisher et al 1954, Synder et al 1955. Concurrent with this, high morphological variation is also noticed in both the species, though the range of variation in the two is different.…”