Serological reactions of pollen incompatibility substances

Abstract

Pollen extracts of 4 incompatibility genotypes (S2.4 S2.6 S3.4 and S3.6) of Oenothera organensis were injected into rabbits to produce antisera. All the unabsorbed antisera gave precipitin reactions with all pollen extracts but the homologous extracts gave stronger reactions. Antisera which had been fully absorbed with pollen extracts heterologous in respect of S alleles gave strong reactions only with extracts which had S alleles in common with the antisera. The results of 25 combinatorial tests, with the exception of 2 cross-reactions, agree with the theory that the S alleles produce specific substances in the pollen each of which is antigenically different. Stigmas were pollinated twice at a 4-hr. interval with incompatible pollen. The pollen tubes from the 2d pollination were not affected by the presence of the 1st lot, indicating that the stylar incompatibility substance is pre-formed and is not the result of an antigenic stimulus from the pollen tubes. Pollen-tube inhibition in the style due to the incompatibility reaction is complete and irreversible at 31[degree]C in 30 min. and after 0.2 to 0.3 mm. growth.