Photosynthetic properties and cross-resistance to some urea herbicides of triazine-resistant conyza canadensis cronq (L.)

E. Pölös, G. Laskay, E. Lehoczki, Z. Szigeti, Sz Pataki

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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-intensity dependences of the rates of CO2 reduction in intact leaves of the R and S plants are very similar. 2) The rate of the Hill reaction of the R chloroplasts at 25°C is 15–20% lower at alllight intensities than that of the S chloroplasts. 3) The rates of the Hill reactions of the 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 discontinuity in 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 of plants 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.

Original languageEnglish
Pages (from-to)783-793
Number of pages11
JournalZeitschrift fur naturforschung - section c journal of biosciences
Issue number6
Publication statusPublished - Jun 1 1987



  • Atrazine and Urea Cross-Resistance
  • Atrazine-Resistance
  • Conyza canadensis
  • Photosynthetic Properties

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)

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