Improved Zn bioavailability by its enhanced colocalization and speciation with S in wheat grain tissues after N addition.

Zinc bioavailability with the presence of other elements in wheat grains might be affected by fertilizers. A long-term field experiment was conducted to examine effects of N fertilizer on Zn bioavailability in wheat grain tissues, with changes in the concentrations, distribution, and speciation of Zn as well as P and sulfur S via synchrotron-based technology. Results showed that addition of N fertilizer was associated with changes in Zn concentrations and distributions in grain tissues, especially in the crease region and endosperm. Simultaneously, N addition enhanced Zn-S colocalization in the crease region and endosperm and lowered the P/Zn ratio and Zn-P colocalization. Addition of N fertilizer with P increased Zn-cysteine (9.2%) and decreased Zn-phytate (47.3%) in the crease region, leading to potentially higher grain Zn bioavailability. Thus, addition of N fertilizer improved concentrations and bioavailability of Zn, by coordinating the relationships among Zn, P and S within wheat grains.