MATERNAL, SINGLE-GENE REGULATION OF ASSIMILATE PARTITIONING IN PEA

Assimilate partitioning has been identified as a key process in the co ntrol of yield. Although the role of reproductive structures in this p rocess has received intensive study, our understanding of the role of the maternal plant is limited. We suggest that the Sn gene of pea (Pis um sativum L.) is a potentially valuable genetic tool for studying mat ernal 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 recessiv e for this gene, and these traits could not be ascribed to reduced car bon assimilation. Flowers of the two nearly isogenic lines were manual ly pollinated to control the genotype of the developing embryo indepen dently of the maternal genotype. The final dry weight of the seed was determined by the genotype of the maternal plant and not by the genoty pe of the embryo, supporting the hypothesis that the Sn gene acts in t he vegetative plant to regulate the partitioning of assimilates betwee n vegetative and reproductive growth. Although the Sn gene has been no ted for delaying apical senescence, it also delayed leaf senescence in this study; leaves of the Sn line continued to photosynthesize long p ast the time that leaves of the recessive line had senesced and after the seeds and pods were dry.