Elemental Imaging of Fertilized ZnO NP Wheat Endosperms Using Laser Ablation–Inductively Coupled Plasma Optical Emission Spectrometry

Zinc (Zn) is an essential trace element in the human body, and its deficiency can seriously affect health. Agronomic Zn biofortification with ZnO nanoparticles (ZnO NPs) in consumable wheat prospectively relieves Zn deficiency. We developed an elemental quantitative imaging laser ablation–inductively coupled plasma optical emission spectrometry method to examine the distributions of Zn and other micronutrient elements in wheat grain and the endosperm. After foliar application of ZnO NPs (four rounds), Zn content in the endosperm can be significantly increased (221 ± 61%), and the Zn, Ca, Mg, and P content gradient decreased from the outside seed coat and aleurone layer to the endosperm, whereas the Fe, Mn, K, Cu, Sr, and Ba content gradient decreased from the crease region to the deeper endosperm. This may indicate how different elements enter the endosperm. Foliar application of ZnO NPs did not change the micronutrient accumulation pattern but did change their contents in wheat grain.