Detection of nickel-induced stress using laser-induced fluorescence signatures from leaves of wheat seedlings

The continuous increase of heavy metal ions in the environment is imposing serious problems in agricultural yield and increases human health threats through accumulation in the food chain. Various studies have shown that heavy metals influence the metabolic processes and pigment concentrations in leaves, and thus affect the laser induced fluorescence (LIF) spectra. Leaf level in vivo LIF spectra using the 488 nm and 355 nm laser lines, fluorescence induction kinetics (FIK) using the 488 nm laser line, and photosynthetic pigments of the control and nickel treated wheat seedlings were measured. The peak parameters of the blue and UV-excited spectral bands were calculated by Gaussian curve fitting. The FIK measured at both the chlorophyll (Chl) fluorescence bands was used to evaluate the fluorescence decrease ratio (R-Fd). The variations in R-Fd and fluorescence ratios of intensities, bandwidth and band area, with varying concentrations of nickel, were revealed as promising parameters in determining the health status of wheat seedlings. These leaf level findings can be extended at canopy level in the field using laser based light detection and ranging (LIDAR) systems.