Serological reactions of pollen incompatibility substances

Abstract

Abstract Pollen extracts of four different incompatibility genotypes S2.4, S2.6, S3.4, 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 twenty-five different combinatorial tests, with the exception of two cross reactions, agree with the theory that the S alleles produce specific substances in the pollen each of which is antigenically different. Stigmas pollinated twice at a 4 hour interval with incompatible pollen showed that the pollen tubes from the second pollination were not affected by the presence of the first lot. This shows that the stylar incompatibility substance is pre-formed and is not the result of an antigenic stimulus from the pollen tubes. Pollen-tube inhibitions in the style due to the incompatibility reaction is complete and irreversible at 31°C in 30 min and after 0⋅2 to 0⋅3 mm growth.