Distribution of the stable isotopes 57Fe and 68Zn in grain tissues of various wheat lines differing in their phytate content
2015
Xue, Yan-Fang | Xia, Hai-Yong | McGrath, Steve P. | Shewry, P. R. (Peter R.) | Zhao, Fang-Jie
BACKGROUND AND AIMS: Cereals are an important source of iron (Fe) and zinc (Zn) for humans, but their concentrations are generally low in white flour (which corresponds to the starchy endosperm) and their bioavailability is limited by high phytate content in the bran. The aim of this study was to investigate whether the phytate content of wheat grain affects the distribution of Fe and Zn to the bran and starchy endosperm. METHODS: The stable isotopes ⁵⁷Fe and ⁶⁸Zn were applied to the flag leaves of four wheat lines differing in their phytate content. The isotopes were also applied to roots of a low phytate line. Isotopic compositions in bran, starchy endosperm and straw were quantified by inductively coupled plasma mass spectrometry. RESULTS: The low phytate line contained approximately half of the phytate-phosphorus concentration of the other three lines. Foliar applications of ⁵⁷Fe and ⁶⁸Zn increased the isotopic ratios ⁵⁷Fe/⁵⁶Fe and ⁶⁸Zn/⁶⁶Zn more in the bran than in the starchy endosperm. The low phytate line did not have a greater distribution of the isotope labels toward the starchy endosperm. The four wheat lines differed in the distribution of ⁵⁷Fe and ⁶⁸Zn from the flag leaves to the rest of the vegetative tissues and the grain. Little of the isotopes applied to roots at the anthesis stage reached the grain. CONCLUSIONS: ⁵⁷Fe and ⁶⁸Zn were preferentially distributed to the bran of wheat grain. Low phytate content in the bran does not appear to facilitate the distribution of ⁵⁷Fe and ⁶⁸Zn into the starchy endosperm.
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