REMOTE-SENSING OF CHLOROPHYLL-A FLUORESCENCE OF VEGETATION CANOPIES .2. PHYSIOLOGICAL SIGNIFICANCE OF FLUORESCENCE SIGNAL IN RESPONSE TO ENVIRONMENTAL STRESSES

Measurements of laser-induced chlorophyll fluorescence of living leaves were compared to ecophysiological parameters, both in near and far field conditions. Near field measurements were carried out with a two-wave-length portable fluorometer, both in the laboratory and in the field. Results show significant changes of the 690 nm and 730 nm chlorophyll fluorescence bands in different environmental conditions. Water stress and carboxylation limitations also affect the fluorescence spectra. Far field measurements from a ground-operated fluorescence LI-DAR system confirm those results. The F690/F730 fluorescence ratio is then demonstrated as a good index for vegetation remote sensing.