Figure 2.

Variation of red scanner band based absolute (A–C) and relative (D–F) SPAD values along the leaf blade of rice under three N rates (0, 150, 225 kg N ha⁻¹) at different growth stages. Absolute SPAD values (A–C) were calculated by Equation (5), in which red scanner band value is the input variable. Normalized SPAD values (D–F) were calculated to identify which part of leaf is sensitive to different nitrogen nutrition status. Quadratic regression was fitted between proportional distance from leaf base (%) and red scanner band based SPAD values (A–C) and relative SPAD values (D–F) by least-squares method with IBM SPSS version 21.0 software.