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Table 1 Correlation coefficients between SPAD readings, leaf nitrogen concentration (LNC, g kg -1 ) and image color related indices (digital number from three color models: RGB, HSV and CIE L * a * b * )

From: Estimating rice chlorophyll content and leaf nitrogen concentration with a digital still color camera under natural light

  SPAD LNC L * a * b * b * /a * H R G B r g b INT VIGreen
SPAD 1.00 0.21 -0.67** 0.78** -0.90** 0.76** 0.83** -0.68** -0.67** -0.48** -0.76** 0.01 0.41** -0.63** 0.66**
LNC 0.32** 1.00 0.48** -0.26* -0.06 0.35** 0.13 0.47** 0.48** 0.63** -0.37** -0.68** 0.65** 0.52** -0.28*
L * -0.62** 0.35** 1.00 -0.83** 0.73** -0.43** -0.63** 1.00** 1.00** 0.96** 0.38** -0.64** 0.21 1.00** -0.90**
a * 0.61** -0.04 -0.70** 1.00 -0.86** 0.50** 0.69** -0.82** -0.84** -0.69** -0.52** 0.18 0.17 -0.80** 0.62**
b * -0.73** -0.35** 0.54** -0.72** 1.00 -0.86** -0.95** 0.74** 0.73** 0.51** 0.87** 0.04 -0.51** 0.68** -0.73**
b * /a * 0.60** 0.48** -0.29** 0.36** -0.91** 1.00 0.96** -0.45** -0.43** -0.18 -0.99** -0.26* 0.72** -0.37** 0.63**
H 0.61** 0.40** -0.39** 0.42** -0.91** 0.97** 1.00 -0.64** -0.63** -0.40** -0.95** -0.09 0.58** -0.58** 0.75**
R -0.63** 0.33** 1.00** -0.68** 0.56** -0.34** -0.44** 1.00 1.00** 0.96** 0.39** -0.64** 0.21 1.00** -0.92**
G -0.62** 0.35** 1.00** -0.71** 0.54** -0.29** -0.39** 1.00** 1.00 0.96** 0.38** -0.64** 0.21 1.00** -0.90**
B -0.37** 0.58** 0.91** -0.47** 0.15* 0.09 -0.03 0.90** 0.91** 1.00 0.12 -0.82** 0.48** 0.98** -0.83**
r -0.56** -0.54** 0.19** -0.35** 0.89** -0.99** -0.95** 0.24** 0.19** -0.20** 1.00 0.36** -0.79** 0.31** -0.56**
g 0.05 -0.66** -0.62** 0.03 0.31** -0.44** -0.34** -0.60** -0.61** -0.87** 0.56** 1.00 -0.86** -0.69** 0.58**
b 0.27** 0.69** 0.27** 0.17** -0.66** 0.79** 0.71** 0.23** 0.26** 0.63** -0.87** -0.90** 1.00 0.29* -0.08
INT -0.56** 0.42** 0.99** -0.64** 0.45** -0.20** -0.31** 0.99** 0.99** 0.95** 0.10 -0.70** 0.37** 1.00 -0.89**
VIGreen 0.67** -0.10 -0.85** 0.42** -0.65** 0.62** 0.68** -0.88** -0.85** -0.68** -0.51** 0.43** 0.02 -0.83** 1.00
  1. Numbers in the upper diagonal were calculated with the Liangyoupeijiu (n = 72) dataset and numbers in the lower diagonal were calculated with the combined data of Liangyoupeijiu, Nanjing45 and Nanjing46 in 2011 (n = 240).
  2. **indicate the significance at P < 0.01, *indicate the significance at P < 0.05.