Abstract: Micronutrient content in wheat (Triticum aestivum L.) grains directly affects human health. However, the regulatory mechanism of micronutrient in grains is not clear.The effect of source and sink manipulation on micronutrient content has not been reported. In this study, 9 winter wheat cultivars were selected to study the regulatory mechanism of micronutrient in wheat grains by reducing source (defoliation and spike shaded) or sink (50% spikelet removal) after anthesis. Changes of Fe, Zn, Mn, Cu, and protein contents in grains and grain weight at maturity were investigated. There were significant differences (P<0.001) on Fe, Zn, Mn, Cu, and protein contents in grains and grain weight among cultivars and among source and sink treatments. In the defoliation treatment, accompanied by the reductions of grain weight (31.9%) and protein content in grains (8.6%), the contents of Fe, Zn, Mn, and Cu in grains were reduced by 1.4%, 4.5%, 7.4%, and 3.7%, respectively. In the spike shaded treatment, grain weight decreased (22.8%) while grain protein content increased slightly (7.9%). The micronutrient contents in grains changed with culti-vars and elements, but the average contents showed increases in Fe (15.8%), Zn (7.1%), and Cu (4.2%) and a decrease in Mn (1.1%). In the treatment of 50% spikelet removal, grain weight was slightly increased by 2.6%, while the grain protein content and Fe, Zn, Mn, and Cu contents rose more obviously by 23.9%, 55.0%, 39.7%, 36.2%, and 13.3%, respectively. The contents of Fe, Zn, Mn, and Cu in grains were restricted by source supplies of the corresponding element, but the effects of the source supply were different across the elements and wheat genotypes. Correlation analysis showed that all coefficients of correlation (r) were significantly positive (r = 0.431-0.785, P<0.01) except that between grain weight and the contents of Cu (r = 0.291, P>0.05) and Fe (r = 0.255, P>0.05). This implies that the 4 micronutrients in grains can be adjusted accordantly and their contents are possibly increased with grain weight and protein content simultaneously.

Key words: Wheat, Source reduction, Sink reduction, Micronutrient content, Grain protein content, Grain weight