A comparison of the photosynthetic activities, chloroplast ultrastructures and sensitivities to some urea herbicides of atrazine-resistant(R)and suspectible (S) biotypes of Conyza canadensis Cronq (L.) (horseweed) in the rosette stage showed that: 1) The light-intensitv dependences of the rates of CO2 reduction in intact leaves of the R and S plants are very similar. 2) The rate of Hill reaction of the R chloroplasts at 25 °Cis 15—20% lower at all light intensities than that of the Schloroplasts. 3) The rates of the Hill reactions ofthe R and S chloroplasts exhibit different temperature-dependences. The activation energy for the S chloroplasts in the temperature range 10—40 °C was found to be 15.3 kJ mol-1. For the R chloroplasts. the discontinuityin the Arrhenius plot was found at around 20 °C; the activation energy was 20.1 kJ mol 1 at below 20°C, and decreased to 8.2 kJ mol-1 at higher temperatures. 4) The R plants have a better adaptive capacity than the S plants at low temperatures. 5) The chloroplast ultrastructure in the R plants was not reminiscent of that ofplants grown under low light intensity. 6) The R biotype exhibited crossresistance to chlorbromuron and metobromuron, and tolerance to linuron. The R and S biotypes, however, were equally sensitive to diuron. The results permitted conclusions on the properties of the triazine-resistance and urea cross-resistance.
|Number of pages||11|
|Journal||Zeitschrift fur naturforschung - section c journal of biosciences|
|Publication status||Published - aug. 1 1987|
ASJC Scopus subject areas
- Biochemistry, Genetics and Molecular Biology(all)