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Self-incompatibility in yellow sweet clover, Melilotus officinalis

Brink, R.A.
Agronomy journal 1934 v.26 no.4 pp. 307-312
pollination, methodology, surface roughness, pods, cross pollination, pollen germination
1. Common yellow, sweet clover, Melilotus officinalis, is shown to be self-incompatible. Under greenhouse conditions about three times as many flowers formed pods after cross-pollination as after self-pollination. 2. The immediate cause of the self-incompatibility is a reduced rate of germination of the pollen of a plant on its own stigma, failure of many of the tubes formed to become established in the style, and the slow growth of those which do penetrate the pistil. Following cross-pollination the pollen grains germinate freely, and the tubes are found in large numbers at the base of the style after 24 hours. 3. While little evidence is available on the point, individual yellow sweet clover plants appear to vary significantly in their norms for self-incompatability. Ordinarily, few seed are obtained on selfing, but the writer has observed two individuals, one isolated in the field and the other grown in a greenhouse, which set seed rather abundantly with their own pollen.