Figure 2
Record section and Young’s modulus of the vibration data associated with the impact test: (A) Position of the micro-electro-mechanical systems (MEMS) sensor array attached to the matured maize plant (cv. LG2533). An impulsive load wave was applied at the bottom of the stem to generate the surface shear waves. (B) Travel time curve for the shear wave (left) across the maize surface (cv. LG2533) and the dispersion curve (right). The travel time curve (solid line) clearly exhibits the different wave velocity in the stem, V1 between S1 to S2 and V2 between S2 and S3. Dispersion curve indicates the presence of a Lamb wave in section S1 to S2, while very small dispersion is present in section S2–S3. (C) Young’s modulus estimated by V1 and V2 based on the linear elasticity. (D) Wave velocities and (E) stalk densities below (S1–S2) and above (S2–S3) the ear for different cultivars. Values in C–E are means ± se (n = 4). Tukey’s HSD test was used to examine the statistical significances at p < 0.05 and different alphabets indicate significant differences. *, **, and *** in (C) indicate significant differences between below- and above-ear stalk sections at p < 0.05, p < 0.01, p < 0.001, respectively, by two-tailed paired Student’s t-test. Values in parentheses above the bars are the ratio of above to below ear sections.
