IN-VITRO MICROPYLAR PENETRATION OF THE POLLEN-TUBE IN THE OVULE OF GASTERIA-VERRUCOSA (MILL) H-DUVAL AND LILIUM-LONGIFLORUM THUNB - CONDITIONS, ATTRACTION AND APPLICATION

Freshly isolated ovules of Gasteria verrucosa and Lilium longiflorum, maintained on agar medium, were used to monitor micropylar penetration of pollen tubes. In Gasteria, the percentage of in vitro micropylar p enetrations is comparable with the penetration percentage in vivo. The penetration efficiency was related to the season, stage of flower dev elopment and method of emasculation. Micropylar penetration in vitro i s independent of the orientation of the micropyle. Multiple pollen tub e penetration occurs as in vivo, and pollen tubes show a preference fo r micropyles with micropylar exudate. All these observations indicate that an attractant is present in this exudate. After washing the ovule s with different solvents before in vitro pollination, the penetration percentage can be influenced. Washing with solvents affecting protein s remarkably influences the rate of penetration, suggesting that the p ossible attractant has a proteinaceous component. Incompatible as well as interspecific and intergeneric pollinations, both for Gasteria and Lilium, were applied and resulted in micropylar penetration. The obse rved penetration of Gasteria pollen tubes in the micropyle of Lilium o vules points to a non-specific micropylar attraction.