Spectral properties of iron-deficient corn and sunflower leaves

Plant response to iron deficiency has been extensively studied, but little is known concerning the effects of iron deficiency-induced modifications in leaf spectral properties. Spectral changes in corn and sunflower plants grown in nutrient solutions containing five iron rates from mg L−1 to 4 mg L−1 were therefore investigated. In both corn and sunflower, iron deficiency decreased leaf dry weight, area, iron concentration, chlorophyll a and b concentrations, and absorptance, increased reflectance and transmittance, and shifted the red edge position of reflectance curves towards shorter wavelengths. Leaf iron concentration was well correlated with leaf chlorophyll a (r = 0.92) and b (r = 0.93) concentrations across crop species. Reflectance was a nonlinear inverse function, and absorptance was a nonlinear increasing function of leaf iron concentration and leaf chlorophyll a concentration. Corn was more sensitive to iron deficiency than sunflower and corn required higher iron concentration than sunflower for optimal growth.