Herbicide Resistant Weeds

Resistance to the herbicide paraquat and increased tolerance to photoinhibition are not correlated in several weed species.

Preston, C., J. A. M. Holtum, and S. B. Powles. 1991. Resistance to the herbicide paraquat and increased tolerance to photoinhibition are not correlated in several weed species. Plant Physiology. 96: 314-318.

Photoinhibition was examined in paraquat-resistant and -susceptible biotypes of Hordeum glaucum, H. leporinum [H. murinum subsp. leporinum], Arctotheca calendula and Conyza bonariensis. Plants were photoinhibited at low temp. (1øC), and the extent of photoinhibition determined by O2 evolution and 77 K fluorescence. No difference in the degree of photoinhibition was detected between paraquat-resistant and -susceptible biotypes for any of the species examined. C. bonariensis plants were also photoinhibited by treatment without CO2 at either 21 or 4% (v/v) O2, and again no difference was observed between the paraquat-resistant and -susceptible biotypes in the reduction of the ratio of variable to max. fluorescence. It was concluded that paraquat-resistant biotypes of the 4 species examined were not more tolerant of photoinhibition than the corresponding paraquat-susceptible biotypes.