Differences in uptake and translocation of foliar-applied Zn in maize and wheat

Background and Aim Success in agronomic biofortification of maize and wheat is highly variable. This study aimed to elucidate the differences in uptake and translocation of foliar-applied zinc (Zn) in maize ( Zea mays L.) and wheat ( Triticum aestivum L.) using different experimental approaches. Methods Old leaves of plants cultured with low or adequate Zn supply in soil were treated with natural Zn (as ZnSO 4 ) or enriched stable isotope 70 Zn as SO 4 salt. Treated leaves, and the remaining untreated shoot and roots were analyzed for Zn using quantitative (ICP-OES and ICP-MS after acid digestion) and qualitative (fluorescence microscopy after Zinpyr-1 staining) techniques. Results Application of Zn to a single old leaf resulted in significantly higher increments in Zn concentration of the treated leaf, remaining untreated shoot and roots in wheat than in maize, particularly under low Zn supply. The relative Zn uptake (i.e., the portion of 70 Zn taken up by the treated leaf) was also estimated to be significantly higher in wheat than maize, irrespective of the rate of Zn supply to plants. Higher uptake and translocation of Zn in wheat compared to maize was also visualized and demonstrated by using Zinpyr-1 fluorescent dye. Conclusions Our results conclude that wheat is superior to maize in terms of leaf penetration and uptake, as well as subsequent translocation of foliar-applied Zn, therefore, the agronomic biofortification potential is better for wheat than for maize.