LASER-INDUCED RED CHLOROPHYLL FLUORESCENCE SIGNATURES AS NUTRIENT STRESS INDICATOR IN RICE PLANTS

Laser-induced red chlorophyll fluorescence spectra of rice leaves were studied using a Jobin Yvon double monochromator. An He-Ne laser was used as the excitation source, and in vivo fluorescence emission spectra were recorded with a resolution of 2 nm in the 650-800 nm range. The fluorescence spectra shows the broad band at 690 nm, with the usually observed broad band around 735 nm resolved into three prominent bands at 725 nm, 745 nm, and 750 nm. In addition, a new band has been observed at 705 nm. The fluorescence induction kinetics (Kautsky effect) were measured at 690 nm, 705 nm, and 725 nm, and the plant vitality index Rfd and the ratios Of fluorescence intensities F690/F705 and F690/F725 were determined for rice grown under normal and nutrient deficient conditions. The results show that the Rfd values and the fluorescence intensity ratios related to the 705 nm band also has great potential for remote sensing stress effects in plants.