Studies on the Nature of Triazine Resistance in Weeds

86 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1982.Triazine susceptible and resistant common lambsquarters (Chenopodium album L.) were grown under non-competitive conditions in a growth chamber. Although the two biotypes had equal leaf areas on a per plant basis, dry matter accumulation at pollination was 9% and 20% less in the resistant plants grown at 600 and 200 (mu)E(.)m('-2)s('-1), respectively. The number of chlorophylls per active photosystem II reaction center was 25 to 30% greater for chloroplasts isolated from these resistant common lambsquarters plants. Specific leaf weight and chlorophyll content per unit leaf area were not different between the two biotypes. Triazine susceptible and resistant biotypes of smooth pigweed (Amaranthus hybridus L.) were grown at varying initial proportions under competitive conditions in the field. Resistant plants were less competitive than susceptible plants as measured by accumulation of aboveground dry weight and seed dry weight. The two biotypes were also grown in the field under non-competitive conditions at 100, 40, and 10% light. Growth rate at 10% light did not differ between susceptible and resistant plants. At the two higher light intensities, dry matter accumulation 11 weeks after seeding was about 40% less in the resistant plants. Relative growth rate and net assimilation rate were lower in the resistant plants by 3.5 and 19%, respectively. The light- and CO(,2)-saturated rate of CO(,2) fixation in intact leaves of glasshouse-grown resistant smooth pigweed was 20% less than that in susceptible smooth pigweed. Specific leaf weight and chlorophyll content per unit leaf area did not differ between the smooth pigweed biotypes grown in the field or glasshouse. The number of chlorophylls per active photosystem II reaction center was higher in chloroplasts from resistant as compared to susceptible plants. However, the 24% increase for resistant plants grown in a glasshouse, and the 22 and 9% increases for resistant plants grown in the field at 100 and 40% light, respectively, did not explain differences between the two biotypes in CO(,2) fixation rate. Various photosystem I and II partial electron transport reactions were conducted in isolated chloroplasts of susceptible and resistant smooth pigweed. Whole chain electron transport rates were the same for chloroplasts from the two biotypes and were high enough to account for in vivo CO(,2) fixation rates (mentioned above), thus indicating that the resistant plants were not limited in photosynthetic electron transport capacity.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD