Minerals
In embryo, contents of K, Ca, Na, Fe, Mn, Cu and Zn decreased as development progressed, while those of Mg and P gradually increased (Figures 5, S9). In endosperm, contents of the nine mineral nutrients decreased as grain filling progressed, being higher at early stage than the later stage. This could be attributed to the dilution effect of grain dry matter, which had a higher rate of accumulation than the minerals (Wang et al., 2018). Compared with endosperm, contents of all minerals were high in the embryo.