Laser-induced imaging of blue/red and blue/far-red fluorescence ratios, F440/F690 and F440/F740, as a means of early stress detection in plants

Green plants exhibit a blue (F440), green (F520), red (F690) and far-red (F740) fluorescence emission. These laser-induced fluorescence (LIF) signatures and ratios allow an early stress diagnosis. The fluorescence ratios blue/red (F440/F690) and blue/far-red (F440/F735) proved to be very sensitive indicators of ongoing stress events. This has been demonstrated by fluorescence emission spectra and the new fluorescence imaging technique. High-light, water and temperature stress as well as nitrogen deficiency, herbicide application, or attacks by mites, etc., can easily be monitored via increasing or decreasing fluorescence ratios and images.