Fig. 6

a–c Water content maps of three leaves, L-a (a), L-b (b) and L-c (c) located at the tip (Fig. 1d), middle (Fig. 1e) and root (Fig. 1f) of the same branch, based on THz technology. The color bar indicates the actual value of THz-based WC, and scale bar in a–c = 1 cm. d, e Contents (histogram, black) and correlation analysis (blue line) of water content of mesophyll (d) and vein (e) measured by THz-based method and the leaf water content measured by gravimetric method, where R² values are 0.99 and 0.89 respectively. In mesophyll, THz-based WC = 1.291 × GWC − 0.211, while in lateral vein, THz-based WC = 1.739 × GWC − 0.457