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. 2017 Aug 22;12(8):e0183262. doi: 10.1371/journal.pone.0183262

Table 7. The best equations and determination coefficients of the relationships across all data (n = 27) between spectral reflectance indices (SRIs) based on the reflectance in NIR/NIR, SWIR/NIR and SWIR/SWIR and the parameters (par.) of total shoot dry weight per plant (TDW), net photosynthesis rate (Pn), stomatal conductance (Gs), and transpiration rate (E).

SRIs Par. Equations R2 SRIs Par. Equations R2
NDVI TDW y = 43.4x2–25.6x + 8.1 0.90 NDWI-2130 TDW y = 2.485e1.82x 0.82
Pn y = 122.9x2–67.5x + 14.4 0.86 Pn y = 35.37x1.65 0.81
Gs y = 1638x2–101.7x + 333.8 0.86 Gs y = 432.76x0.807 0.75
E y = 11.2x2–5.1x + 5.5 0.10 E y = -29.7x2 + 34.8x - 3.8 0.12
WI TDW y = 0.085e4.065x 0.31 NDMI-1 TDW y = 23.105x2.24 0.80
Pn y = 0.0067e7.01x 0.29 Pn y = 105.41x3.87 0.75
Gs y = 6.172e3.48x 0.28 Gs y = 733.77x1.88 0.69
E y = 2.99x + 2.71 0.03 E y = -85.5x2 + 108.3x - 27.8 0.12
NWI-3 TDW y = 3.806e-15.56x 0.64 MSI TDW y = 15.58e-1.57x 0.84
Pn y = 4.44e-28.19x 0.65 Pn y = 55.17e-2.78x 0.82
Gs y = 157.62e-13.67x 0.59 Gs y = 533.5e-1.34x 0.74
E y = -18.78x + 5.24 0.02 E y = -2.76x + 7.42 0.05
NDWI-1240 TDW y = 27.20x0.54 0.63 RWC;RSI TDW y = 14.18e-2.01x 0.74
Pn y = 130.7x0.91 0.56 Pn y = 48.44e-3.66x 0.76
Gs y = 856.76x0.46 0.56 Gs y = 504.39e-1.79x 0.70
E y = -1798.7x2 + 275.6x - 3.3 0.17 E y = -49.8x2 + 32.1x + 1.5 0.21
REM TDW y = 3.77e0.14x 0.86 NDMI-2 TDW y = -16.3x2–28.1x - 2.9 0.71
Pn y = 4.37e0.25x 0.88 Pn y = -61.4x2–99.0x - 19.9 0.70
Gs y = 160.07e0.12x 0.73 Gs y = -668.6x2–1075.8x - 97.4 0.66
E y = 0.19x2–0.99x + 6.2 0.22 E y = -28.1x2–31.8x - 2.5 0.14
RMSI TDW y = -1.42x2 + 8.5x - 3.5 0.77 RWC;NDSI TDW y = 13.137x0.91 0.79
Pn y = -5.57x2 + 30.7x - 22.7 0.72 Pn y = 40.99x1.62 0.78
Gs y = -67.8x2 + 359.9x - 150.8 0.67 Gs y = 463.06x0.79 0.71
E y = -2.35x2 + 9.9x - 3.8 0.16 E y = -41.6x2 + 45.3x - 5.7 0.17
SWWI TDW y = 12.09x0.42 0.84 NDTI TDW y = 29.007x1.17 0.54
Pn y = 35.71x0.77 0.84 Pn y = 133.97x1.90 0.45
Gs y = 426.49x0.36 0.72 Gs y = 906.52x0.99 0.48
E y = -32.4x2 + 21.1x + 3.1 0.13 E y = -121.5x2 + 70.9x - 4.1 0.02
NDII TDW y = 12.07x0.42 0.81 CAI TDW y = 16.91e3.84x 0.73
Pn y = 36.22x0.77 0.84 Pn y = 61.072e6.62x 0.68
Gs y = 433.21x0.37 0.75 Gs y = 565.81e3.24x 0.63
E y = -34.23x2 + 22.45x + 2.8 0.14 E y = -141x2–61.1x - 0.15 0.11