|
As a part of an ongoing laser induced fluorescence (LIF) project, out laboratories have developed a fluorescence imaging system (FIS) to acquire fluorescence images at wavelengths centered at 450 nm, 550 nm, 680 nm, and 740 nm. The system consists of ultraviolet (UV) fluorescent lamps as an exciting source, automated filter wheel, and charge coupled device (CCD) camera. The automated filter wheel and CD camera are controlled by a microcomputer via a computer interface,a nd digital images are captured. The FIS is capable of capturing steady state fluorescence and chlorophyll fluorescence induction images. Experimental studies were conducted to demonstrate the utility of the FIS. One such study included experiments to observe the effects of ethylenediurea (EDU) in soybean leaves with FIS. Five different concentrations of EDU were sued to establish a doe-response relationship. Although visual effects of EDU treatment were not apparent, the intensities of the fluorescence images of the plant leaves varied depending on the EDU concentration, the location on the leaf surface and the emission wavelength. EDU appeared mainly to affect the photosynthetic apparatus causing non-uniform increases in red and far-red fluorescence. Ratio images of red-green and blue/far-red were found to be sensitive indicators in detecting EDU effects. A ratio of fluorescence induction to steady state fluorescence had a curvilinear relationship with EDU-dosage. Such kinetic measurements can be used to assess photosynthetic activity in response to a range of chemical and environmental stresses. This study demonstrates that FIS is an excellent tool to detect stress symptoms before the onset of visible injury. It will enhance our understanding of the interactions among photosynthetic activity, vegetative stresses and fluorescence responses. Characterization of steady state fluorescence patterns in leaves is of significant value in our LIF research studies, and images taken with FIS greatly complement non-imaging fluorescence measurements by finding the spatial distribution of fluorescence in leaves.
|
