Fluorescence Properties of Paraquat Resistant Conyza Leaves

Fluorescence parameters /Fv, Fs, Fo, Rfd/ derived from fast and slow induction curves of paraquat treated susceptible and resistant Conyza plants were investigated by a newly developed micro-computerized apparatus. Resistant plants sprayed with Gramoxone /4 μM paraquat/ showed a transient inhibition which means that paraquat can penetrate into the chloroplasts. The recovery of the fluorescence parameters began 2 h after spraying, and it was completed in more than 48 h. pI50 values of induction parameters were determined in Conyza leaves floated on paraquat solution of different concentration for 24 h. Fv and Rfd values were the most sensitive parameters giving a resistance factor of about 3oo and more than 450, respectively.