Effect of hexane and humidity on self-incompatibility in Brassica oleracea

The effects of hexane, high humidity, flower age and temperature in overcoming the self-incompatibility of Brassica oleracea were studied using three plants, each of which was homozygous for a different dominant S-allele. Hexane had a significant effect in all cases, but the size of the effect varied considerably. In one plant there was a marked interaction between the effect of hexane, humidity and flower age, but temperature had relatively little effect. In another plant high humidity alone gave a very much greater response than hexane alone. This plant gave as many self-seeds from the high humidity treatment as from bud selfing, indicating that the incompatibility reaction was almost completely overcome by the high humidity. The results are discussed in the light of current views of the mechanism of incompatibility in Brassica.