Pollen-ovule ratio (P/O) of the angiosperms, the ratio of pollen grains to ovules, can reflect more indications than floral morphology for the breeding systems.

• 摘要花粉-胚珠比系指开花植物之花粉数与胚珠数的比值，对植物之繁殖系统较花之形态更具有指标作用。