THE EFFECT OF LECTINS ON GERMINATING POLLEN OF LILIUM LONGIFLORUM I. EFFECT ON POLLEN GERMINATION, POLLEN TUBE GROWTH AND ORGANIZATION OF MICROFILAMENTS

Five lectins were tested for their binding capacity to pollen tubes of Lilium longiflorum and for their effect on pollen germination and pollen tube growth. Only Concanavalin A (Con A) and Helix pomatia agglutinin (HpA) showed strong binding to the cell surface, in particular to the colpus of the pollen grain and to the tip of the pollen tube. Wheat germ agglutinin, phytohaemagglutinin and Ulex europeus agglutinin showed hardly any binding. No noticeable differences in binding capacity were observed between pollen tubes grown ‘in vitro’ or ‘in vivo’ and between pollen tubes regained after compatible or incompatible pollination. ‘In vitro’ germination of pollen increased at low Con A concentrations (up to 50 μg/ml), but it was inhibited at higher concentrations. Pollen tube growth was inhibited both at low and high Con A concentrations. HpA caused a slight increase in pollen germination, but did not influence pollen tube growth. The other lectins had no effect. When germinated pollen was supplied with Con A, a disorganization of the microfilamental strands was observed in the tip region of the pollen tubes.