Diagnosis of acute injury of wheat caused by SO₂ using color parameters of wheat digital images

Experiments were conducted in an open-top fumigation device. Samples of wheat were exposed to elevated sulfur dioxide concentrations of C₁(27.2 mg/m³), C₂(41.3 mg/m³), C₃(68.3 mg/m³), C₄(81.3 mg/m³) and C₅(94.3 mg/m³). Images of wheat expended leaves injured by SO₂, were taken using digital camera, at the same time the environmental light intensity was measured. Then the color parameters RGB of wheat leaves were extracted from those digital images to study the correlation between color parameters and the SO₂ concentration. The results showed that values of RGB increased with the elevated SO₂ concentrations, which indicated that acute injury of wheat caused by SO₂ impacted the reflectance spectral characteristics of visible light of wheat leaves. Although there was an insignificant correlation between RGB and SO₂ concentrations, ratio vegetation indices of color parameters to light intensity (called CLRVI) were strongly negative logarithmic correlation with SO₂ concentrations (R²>0.859) at 0.01 confident level. As a result, color parameters RGB extracted from digital images could be used to diagnose the acute injury of wheat caused by SO₂ at various concentrations.