On the Experimental Manufacture of a Surface Light source for the Excitation of Pigment in Plant Leaves by using Ultraviolet Light Emitting Diodes

Abstract

This work is the continued research of "Performance evaluation of ultraviolet light emitting diodes as an excitation source in fluorescence measurement of plant leaves, bulletin of KNCT, vol.40, pp.53-62 (2007)". We have made excitation surface light sources for plant pigment by using new ultraviolet light emitting diodes (NSPU510CS, NICHIA). The irradiance and the radiation distribution of surface light sources were simulated based on the data in UV-LED unit. Then, two prototypes were made as results of simulation. Experimental data and the simulated results were well consistent with each other. Fluorescence spectra of peanut leaves were measured excited by the prototype with an UV-pass filter. Normal fluorescence spectra that contained no radiation of UV-LEDs in visible region (400 nm-800 nm) were obtained. However, the fluorescence spectra had changed depending on the irradiance of surface light sources especially in the region of under 50 Wm-2. This irradiance dependence can be significant obstruction to evaluate plant stress from the fluorescence spectral changing. Therefore, the development of the UV-LEDs light source with higher irradiance is necessary in future.