Delayed light imaging for the early detection of plant stress.

Image-intensified photographs of delayed light emission (DLE) from soybean leaves exposed to sulfur dioxide showed evidence of the stress that developed during the exposure period. A comparison of DLE images taken during the fumigation with a conventional photograph taken 5 days later showed a clear correspondence between leaf areas that had the most diminished DLE intensity and those that showed the greatest visible injury. These results suggest that DLE imagery will be a useful tool in the investigation of the spatial distribution and temporal development of plant stress.