- In vivo spectral analysis of radish leaves sought effects on radish light harvesting apparatus (LH) of the herbicides: clomazone (FMC57020; [2-(2-chlorophenyl) methyl-4,4 dimethyl-3-isoxalidinone), diuron (DCMU; [3-(3,4-dichlorophenyl)-l,ldimethylurea)] and amitrol (H-1,2,4-triazole-3-amine). All herbicides used cause visual symptoms of chlorosis or damage chloroplast membranes and thus disrupt LH structure. The spectra were obtained at early stages of the chlorotic effect. The spectra was analyzed by the fourth derivative technique. The frequency of occurrence of fourth derivative maxima was analyzed statistically. Statistical analysis of peak frequency showed multiple and complex changes occurred in LH spectra in response to herbicide treatment. Amitrol effects were readily apparent and are those described here. The most prominent effect of amitrol was the narrowing and apparent red shift of LH component Cb 670 (French C.S., Brown J.S. and Lawrence M.C., 1972. Plant Physiol., 49, 421-424.). Further analysis of Cb 670 revealed fine structure consisting of at least three bands (Cb 670a., Cb 670b and Cb670c). The effects of amitrol on this system resulted in the loss of two fine structure bands (Cb 670a, Cb 670c). The result is that the remaining fine structure band (Cb 670b) dominates the spectral envelope of the parent band (CB 670) causing parent band narrowing and red shift. Since plant response to herbicides reveals the presence of these chemicals, this effect may be useful in herbicide detection.