TOLERANCE OF CULTURED AMARANTHUS-RETROFLEXUS CELLS TO ATRAZINE

Resistance to s-triazine-herbicides in weeds is the most widespread an d extensively studied of all intraspecific herbicide-resistance. It is of interest that the resistant biotype appears in some limited genera such as Amaranthus spp. and Chenopodium spp. much more frequently tha n in many other significant weeds. We examined the response of culture d Amaranthus retroflexus cells to atrazine in comparison with those of several other plant species to understand what causes this differenti ally inter-specific response. Atrazine scarcely inhibited the cell gro wth of either atrazine-resistant and susceptible-Amaranthus cells. Tob acco cells, however, could not grow as cultured Amaranthus cells in hi gh concentrations of atrazine even under heterotrophic culture conditi ons. Atrazine-resistant tobacco cells were also sensitive to high conc entrations of atrazine. The inhibition of cell growth by this secondar y effect of atrazine was also observed in cultured wheat and rice cell s. Atrazine-sensitive Chenopodium cells are relatively more resistant to high concentrations of atrazine. The importance of potential tolera nce to the secondary effects of atrazine is discussed with respect to the frequent occurrence of triazine-resistant biotypes in limited plan t species.