Effect of chlorfenprop-methyl, flamprop-isopropyl and benzoylprop-ethyl on 14C2 fixation in Avena fatua L., Triticum aestivum L. and Hordeum vulgare L.

The effect of chlorfenprop-methyl, flampropisopropyl and benzoylprop-ethyl on ¹⁴CO₂ fixation was followed in wild oat (Avena fatua L.), barley (Hordeum vulgare L., cv. Ametyst), and wheat (Triticum aestivum L., cv. Mironovská). Experimental plants were exposed to a ¹⁴CO₂-enriched atmosphere in a special apparatus 2 h, 1, 3, and 9 days after the herbicide treatment. Chlorfenprop-methyl already inhibited ¹⁴CO₂ fixation in wild oat plants 2 h after the treatment. ¹⁴C-metabolite transport to the roots was strongly decreased. Both ¹⁴CO₂ fixation and ¹⁴C-metabolite level in the roots were significantly depressed in A. fatua when compared with untreated plants at the last sampling time. ¹⁴C incorporation into starch was inhibited from the first day after treatment, and on day 9 was lowered more than ten fold in treated plants. Flamprop-isopropyl inhibited ¹⁴CO₂ fixation in wild oat plants from day 3 after treatment, but benzoylprop-ethyl not until day 9. Both herbicides also decreased ¹⁴C incorporation into starch in A. fatua. Chlorfenprop-methyl also slightly decreased ¹⁴CO₂ fixation in barley on day 9. However, assimilate transport into the roots and ¹⁴C incorporation into starch were not affected. Flamprop-isopropyl inhibited ¹⁴CO₂ fixation in barley plants only on the first day after treatment, and assimilate transport was also reduced. By contrast, no differences from untreated plants were found at the end of the experiment. Benzoylprop-ethyl did not decrease either ¹⁴CO2 fixation or assimilate transport to the roots in wheat, but it inhibited starch synthesis. Atrazine depressed ¹⁴CO₂ fixation in wild oat plants by 91%, in wheat plants by 99% compared with untreated plants. Assimilate transport into the roots was also strongly inhibited. In contrast to atrazine, the effect of chlorfenprop-methyl, flamprop-isopropyl, and benzoylprop-ethyl on CO₂ fixation seems to be secondary.