Fig. 1. Ca, Al, and Si intensity profiles over a cross-section of a rice grain^[28](the color bar in the upper right corner indicates that the abundance of an element increases from purple to red)

Fig. 2. Calibration plot of untreated data points and surface-density-normalized calibration plot of Mg element determined by LIBS^[35]. (a) Calibration plot of untreated data points;(b) surface-density-normalized calibration plot