POLLEN VIABILITY, VIGOR, AND COMPETITIVE ABILITY IN ERYTHRONIUM-GRANDIFLORUM (LILIACEAE)

To determine how the capability of pollen is affected by lengthy expos ure to field conditions, we obtained pollen samples (from Erythronium grandiflorum) that were fresh (from newly dehisced anthers) or aged, f rom 6 to 24 hr. Without pretreating the collected grains, we compared their abilities 1) to retain viability, as indicated by the Heslop-Har rison fluorochromatic reaction (FCR) test; 2) to retain germinability, as indicated by pollen-tube growth in vitro on Brewbaker-Kwack medium ; 3) to sire seeds when used as a pollen donor on recipient flowers in the field; and 4) to sire seeds competitively when mixed with another donor pollen in competitive pollinations. FCR scores declined drastic ally with pollen age. Germinability typically declined with age, but l ess drastically; the correlation between FCR and germinability ranged from strong to nil in different trials. The sharp decline in FCR was p robably due to nonlethal, reversible desiccation. Seed-siring success, both in competitive and noncompetitive trials, bore no relation to po llen age or to germinability. Any loss in seed-airing ability in E. gr andiflorum pollen over 24 hr is apparently overwhelmed by other source s of variation. The lack of correlation between seed-siring ability an d FCR or germinability scores means that those tests should not be use d to estimate overall pollen competence in this species. They should b e so used in other species only if experiments have demonstrated their greater reliability.