Uptake of the herbicide diuron as visualised by the fluorescence imaging technique

A new fluorescence imaging system for monitoring the uptake of the PSII-herbicide diuron (DCMU) was tested in tobacco leaves. UV-laser-induced (lambda(exc) = 355 nm) fluorescence images were collected for blue fluorescence F440 (lambda(em) = 440 nm), green fluorescence F520 (lambda(em) = 520 nm), red chlorophyll fluorescence F690 (lambda(em) = 690 nm) and for far-red chlorophyll fluorescence F740 (lambda(em) = 740 nm). Diuron-treated leaf parts exhibited a higher red and far-red chlorophyll Fluorescence emission (F690 and F740) than untreated leaf halves, whereas the blue and green fluorescence, F440 and F520, remained unaffected. As a consequence, the fluorescence ratios blue/red (F440/F690) and blue/far-red (F440/F740) significantly decreased in diuron-treated leaf parts. The time course of diuron uptake into the leaf could be followed by fluorescence images taken 10 and 30 min after diuron application. The novel high resolution fluorescence imaging method supplies information on the herbicide uptake of each point of the leaf area. Its great advantage as compared to the point data fluorescence measurements applied so far is discussed.