Distribution of iron, manganese, and zinc in mature grain and their mobilization during germination and early seedling development in maize

Distribution of iron (Fe), manganese (Mn), and zinc (Zn) in mature grains of maize (Zea mays L.) of 25 genotypes was studied. The highest concentrations of micronutrients were found in the seed coats and scutellum, while the lowest were found in the endosperm. The endosperm, scutellum, and seed coats contained between 60-80%, 15-35%, and 8-12% of the total grain micro-nutrients, respectively. Mobilization of Fe, Mn, and Zn from the scutellum and endosperm was studied in four genotypes of maize during 3-120h of germination and early seedling growth. Variation in original concentrations in the scutellums of the genotypes exceeded that observed in the endosperms. Genotypes were separated into several groups with high-Fe (144-168 mug g(-1)) and high-Zn (89-94 mug g(-1)) scutellurn (cvs. Brewero yellow, Corriente de gallina), high-Mn (40-42 mug g(-1)) scutellum (cvs. Pusey blond, Brewero yellow), low-Fe (107-110 mug g(-1)) and low-Zn (76 mug g(-1)) scutellum (cvs. Pusey blond, Oregon grewn), and low-Mn (33-36 mug g(-1)) scutellurn (cvs. Oregon grewn, Corriente de gallina). The type of kernel tissue influenced micronutrient mobility during germination. The highest share of freely leaked forms of micronutrients was generally observed for the genotypes with high-micronutrient scutellum. After the radicle protruded, the efflux of micronutrients from the scutellum was not dependent with original metal concentrations. The genotypes studied did not differ in the total efflux of minerals from the grain (endosperm + scutellum) measured 120 hr after grain soaking. The following sequence characterized efficiency of kernel-born metals utilization by the seedling: Fe < Mn greater than or equal to Zn. Efficiency of mobile Zn utilization was specific to the growth of genotype. This index was found lowest for cvs. Brewero yellow and Pusey blond with low-weight seedlings. Removal of seed coats after 3 days of grain soaking did not influence dynamics of micronutrients in grains and seedlings of cv. Mestnaya. The possible pathways of micronutrient transport in seedlings are discussed in relation to original micronutrient distribution within the grain.