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Comparison of Zn accumulation and speciation in kernels of sweetcorn and maize differing in maturity
Citation:
Cheah, Z., P. Kopittke, K. Scheckel, M. Noerpel, AND M. Bell. Comparison of Zn accumulation and speciation in kernels of sweetcorn and maize differing in maturity. Annals of Botany. Oxford University Press, Cary, NC, 125(1):185-193, (2020). https://doi.org/10.1093/aob/mcz179
Impact/Purpose:
The aim of the present study was to examine the accumulation and speciation of Zn within sweetcorn and maize kernels at different stages of maturity. First, we determined the Zn concentration and content of embryo and endosperm tissues in 12 varieties of sweetcorn and three varieties of maize at the immature stage (21 DAP) corresponding to the time of sweetcorn consumption. Next, using one variety of sweetcorn and one variety of maize, we examined the change in the Zn concentration and content within these two tissues of sweetcorn and maize over five different stages of kernel maturity. Finally, we used synchrotron-based X-ray absorption spectroscopy (XAS) for the in situ examination of the speciation of Zn within the embryo and endosperm. This information is critical in understanding how these two major crops contribute to the dietary Zn nutrition of consumers.
Description:
• Background and Aims Understanding the speciation of Zn in edible portions of crops helps identify the most effective biofortification strategies to increase the supply of nutrients for improving the health and nutrition of consumers. • Methods Kernels of 12 sweetcorn and three maize (Zea mays) varieties were analysed for Zn concentration and content. The speciation of the Zn in the embryos, endosperms and whole kernels at 21, 28 and 56 days after pollination (DAP) was then examined for one maize and one sweetcorn variety using synchrotron-based X-ray absorption spectroscopy (XAS). • Key Results Averaged across all sweetcorn and maize varieties at 21 DAP, the embryo contributed 27–29% of the whole kernel Zn whilst the endosperm contributed 71–73 %. While sweetcorn embryos contributed a lower proportion to the total kernel Zn than those of maize, the proportion of total Zn in the embryo increased as kernels aged for both varieties, reaching 33 % for sweetcorn and 49% for maize at 28 DAP. Using XAS, it was predicted that an average of 90 % of the Zn in the embryos was present as Zn-phytate, while in the endosperm the Zn was primarily complexed with an N-containing ligand such as histidine and to a lesser extent with phytate. However, in maize endosperms, it was also observed that the proportion of Zn present as Zn-phytate increased as the kernel matured, thereby also probably decreasing its bioavailability in these mature maize kernels. • Conclusions The apparent low bioavailability of Zn supplied in maize at its consumption stage (i.e. mature kernels) probably undermines the effectiveness of biofortification of this crop. Conversely, successful biofortification of Zn in sweetcorn and green maize consumed as immature kernels could potentially provide a good source of bioavailable Zn in human diets.
URLs/Downloads:
DOI: Comparison of Zn accumulation and speciation in kernels of sweetcorn and maize differing in maturity
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