FLUORESCENCE EMISSION-SPECTRA OF PARAQUAT-RESISTANT CONYZA-CANADENSISDURING THE CHLOROPHYLL FLUORESCENCE INDUCTION AS DETERMINED BY THE CCD-OMA SYSTEM

A multichannel chlorophyll spectrofluorometer based on a charge couple d device (CCD-OMA fluorosensor) was used for fast screening of the chl orophyll fluorescence characteristics of paraquat sensitive (S) and pa raquat resistant (PqR) horseweed (Conyza canadensis) biotypes. It is d emonstrated that S and PqR plants can easily be distinguished already from some leaf samples by only one series of fluorescence spectra meas urements. The chlorophyll fluorescence parameters Fm, Fs, and the chlo rophyll fluorescence ratios Rfd and F690/735, calculated from the spec tra taken at different times during the fluorescence induction kinetic s, clearly indicate the different paraquat sensitivity of the two hors eweed biotypes. With the fluorosensor it was also shown that the paraq uat resistant planes were, however, sensitive to the herbicide diuron. The results are in good agreement with earlier results achieved by mo re sophisticated and time consuming methods.