Maternal, single-gene regulation of assimilate partitioning in pea

Assimilate partitioning has been identified as a key process in the control of yield. Although the role of reproductive structures in this process has received intensive study, our understanding of the role of the maternal plant is limited. We suggest that the Sn gene of pea (Pisum sativum L.) is a potentially valuable genetic tool for studying maternal regulation of partitioning. In this study, nearly isogenic lines differing at the Sn locus were compared with respect to seed-filling characteristics and carbon assimilation. Lines with the Sn gene had a slower rate and shorter duration of seed growth than the line recessive for this gene, and these traits could not be ascribed to reduced carbon assimilation. Flowers of the two nearly isogenic lines were manually pollinated to control the genotype of the developing embryo independently of the maternal genotype. The final dry weight of the seed was determined by the genotype of the maternal plant and not by the genotype of the embryo, supporting the hypothesis that the Sn gene acts in the vegetative plant to regulate the partitioning of assimilates between vegetative and reproductive growth. Although the Sn gene has been noted for delaying apical senescence, it also delayed leaf senescence in this study; leaves of the Sn line continued to photosynthesize long past the time that leaves of the recessive line had senesced and after the seeds and pods were dry.