Ethylene and the annona flower.

The annona (Annona hybrida) flower is protogynous, and reaches its male stage about 26 hours after the beginning of the female stage. A rise in ethylene production was found to precede the male stage. Much more ethylene was produced by the reproductive organs than by the petals, with the anthers producing most of the ethylene. Ethylene treatments advanced the male stage, but not the female stage. Exposing flowers to hypobaric pressure postponed the onset of their male stage. Application of various growth substances causing ethylene production by the flower advanced the male stage.