Paternal effects on seed mass in Arabidopsis thaliana.

Who is in control of seed size, and do some fathers sire bigger seeds than others? We used isogenic male-sterile genotypes of the Arabidopsis thaliana accessions Col and Ler. By fertilising flowers side-by-side with either pollen from the same accession ('self-pollination') or pollen from another accession (outcrossing), we compared, on the same mother plant, seed set of flowers that were very similar in resource status. Some paternal genotypes had a significant effect on seed mass, with the most extreme father siring seeds 15.3% heavier than seeds resulting from 'self-pollination'. There was no correlation between seed mass of paternal parents and the seeds they sired. We discuss the evolution of seed size as a tug-of-war between parent and offspring.