Abscisic acid and assimilate partitioning to developing seeds. II. Does abscisic acid influence the sink strength of Arabidopsis seeds?

The role of abscisic acid (ABA) in the regulation of transport of assimilates to seeds was investigated with the aid of Arabidopsis thaliana mutants that were ABA-deficient and/or insensitive to ABA. Subsequent flowers of mutant mother plants were alternately pollinated with pollen from either wild-type or mutant plants, and the transport of radiolabelled photoassimilates to the genetically different seeds was studied. The experiments were performed under conditions of reduced availability of source material, achieved either by reduced light quantity or by combining the ABA-deficient mutant with a starchless mutant. No effect of the genotype on the import rate of assimilates was detected, indicating that endogenous ABA does not influence the sink strength of Arabidopsis seeds. Reports describing contrary results are discussed.