NUTRIENT STRESS OF CORN PLANTS: EARLY DETECTION AND DISCRIMINATION USING A COMPACT MULTIWAVELENGTH FLUORESCENT LIDAR

Abstract

The objectives of this study were to assess the capability of laser-induced fluorescence (LIF) to discrimi-nate between nitrogen and sulfur deficiencies in corn that result in similar effects on leaf colour, and to de-termine the relationship between changes in LIF emission spectra and plant growth inhibition. Corn plants were grown in the greenhouse and fertilised for 35 days with nutrient solutions of different nitrogen (N) and sulfur (S) concentrations. Every 6 to 8 days during the experiment, fluorescence data were remotely ob-tained using an FLS-PL compact multiwavelength fluorescence lidar developed by our group. Excitation wavelengths varied from the UV to the VIS spectral range over the measurement cycle. The corresponding fluorescence spectra were recorded at each laser pulse with a CCD-based multi-channel detector. On the same day as the fluorescence measurements were made, the leaf reflectance was measured and leaf sam-ples were collected for the N, S and chlorophyll {a+b} (Chl{a+b}) content analyses. N deficiency caused a significant decrease in the accumulation of plant biomass and the Chl{a+b} leaf contents after 6 days of treatments, whereas S deficiency led to significant decreases in Chl{a+b} leaf contents and the accumulation of plant biomass after 6 and 18 days of treatments, respectively. The losses of Chl{a+b} in N- and S-deficient plants were similarly correlated to the changes in the R740/R540 re-