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Abstract
The role of both acidity release and ferric reduction by scutellum was investigated in relation to iron (Fe) mobilization from endosperm and transport to axis organs (shoot + root) during early seedling development of maize (Zea mays L.). Effect of scutellum zinc (Zn) transfer to growing axis organs was also evaluated. Acidity release and translocation of Fe or Zn from an agar medium to axis organs were decreased when scutellum dorsal sides of intact seedlings were embedded into a pH buffered agar medium. Across genotypes root growth during at least 3 days was correlated to scutellar acidity release. Orthovanadate or pyrazole (1 mM) did not inhibit Fe translocation to axis organs. Thus, Fe translocation was not closely associated with scutellum plasma membrane H+-ATPases or alcohol dehydrogenase. Addition of Fe2+-citrate facilitated Fe translocation from agar medium to axis organs by 20%, compared to FeSO4. Extracellular reduction of Fe2+ to Fe3+ was associated with release of reductants from scutellum, which was dramatically inhibited by low temperature (7°C). This process was not affected by solution pH within range of 3.5–6.5 units or by copper (Cu2+), Zn2+, and manganese (Mn2+) added to assay-solution Fe.
