Rice grain Fe, Mn and Zn accumulation: How important are flag leaves and seed number?

Flag leaves play an important role in synthesis and translocation of photoassimilates in the rice plant, affecting grain yield; similarly they were believed to be a major source of remobilized minerals for the seeds. At the same time, the seed's sink strength plays an important role in dry matter accumulation. To investigate the relative contribution of rice flag leaves and seed sink strength to seed mineral accumulation, field experiments were conducted to evaluate the effect of flag leaf or half-seed removal on seed Fe, Mn and Zn concentration and content. Flag leaf or 50% of the seeds were removed at anthesis. Seed Fe, Mn and Zn accumulation were not affected by flag leaf or second leaf removal. Plants with only half of the seeds showed higher Fe and Zn seed concentrations, but similar Mn concentrations. It is concluded that the flag leaf is not necessary for metal remobilization to the seeds and that seed sink strength and seed number have different roles in Fe/Zn and Mn seed concentrations.