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Thermoluminescence (TL) after continuous illumination was studied in untreated and herbicide treated (atrazine, 2-chloro-4-ethyla-mino-6-isopropylamino-s-triazine; DCMU, N-(3-4-dichlorophenyl)-N-N-dimethyl-urea; DNOC, dinitro-o-cresol) chlosoplasts of triazine-susceptible and -resistant biotypes of Erlgeron canadensis L. The results obtained from the above experiment can be summarized in the following manners:
1. TL can be applied in the approximate determination of I50 value of photosystem II (PS II) herbicides in the treated plants.
2. In the susceptible chloroplasts herbicide binding influences the redox state of the primary quinone electrone acceptor QA, which is reflected on the peak position of the main TL band.
3. TL investigation illustrated that the action sites of urea-type (DCMU and atrazine) and phenolic (DNOC) herbicides are in interaction with each other. DCMU and atrazine can replace DNOC from its binding site of the chloroplast membrane.
4. In the susceptible biotype the main TL band which is related to the secondary quinone electron acceptor QB (QB-band) apeared at +30°C. This band is totally absent in the resistant biotype.
5. In the resistant biotype a TL band at +10°C can be observed which is assigned to the primary acceptor QA (QA-band).
