The flower, Sterility Mechanisms, and Pollination Control

Alfalfa has a highly specialized papilionaceous flower with a unique tripping mechanism that limits the type of insects that can effectively trip it. The alfalfa flower has a unique floral morphology and tripping mechanism. The floral morphology encourages cross-pollination; however, a high frequency of self-pollination can occur. Cross-pollination produces more pods per flower tripped and more seeds per pod than does self-pollination. Self-fertility can be effectively measured as percentage of tripped flowers producing pods, number of seeds per pod, or number of seeds per flower tripped. Normal pollen germination and pollen tube growth can be obtained in vitro on a basic medium that includes only sugar and agar. In vitro pollen tube length appears to be correlated with in situ growth. Two male-sterility systems exist in alfalfa.