Figure 4

Calibration of the four models in Table4for the estimation of leaf nitrogen concentration (LNC, g kg^-1) and SPAD. Model 1 (a), LNC = αSPAD + βDAT + γ, model 2 (b), LNC = αb^* + βDAT + γ, model 3 (c), SPAD = αb^* + βDAT + γ, model 4 (d), SPAD = αb^* + γ. Different colors denote different developmental stages (red: vegetative, green: tillering, blue: jointing, purple: booting). Different symbols denote different cultivars used for model calibration (○ Liangyoupeijiu, ∆ Nanjing45, □ Nanjing46).