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Media type:
E-Article
Title:
Apomixis in Side-Oats Grama
Contributor:
Harlan, Jack R.
imprint:
American Botanical Society, 1949
Published in:
American Journal of Botany, 36 (1949) 7, Seite 495-499
Language:
English
ISSN:
1537-2197;
0002-9122
Origination:
Footnote:
Description:
<p>A bulk source strain of side-oats grama derived from a collection from Southern Arizona and exhibiting a considerable variation was found to reproduce asexually. This strain is described and reported here under the name of the "Tucson" strain of side-oats grama. Progenies from single plant selections are extremely uniform in appearance compared to similar progenies from other strains. Chromosome numbers were observed to vary from 85-101, and showed very little pairing at meiosis. In microsporogenesis the first division is regularly asymmetrical, the homologues of the several bivalents separating from the remainder of the chromosomes. In the second division the daughter cell containing the bivalent homologues divides regularly, while the other daughter cell may divide irregularly producing from two to eight sporads with consequent variability of pollen grains. The apomictic mechanism is based upon the same type of asymmetrical division reported for microsporogenesis, the meiotic products being two approximately unreduced cells and two cells with only a few chromosomes each. The evolutionary significance of apomixis in the species is discussed.</p>