Tolerance of Cultured Amaranthus retroflexus Cells to Atrazine

Abstract

Resistance to s-triazine-herbicides in weeds is the most widespread and 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 than in many other significant weeds. We examined the response of cultured Amaranthus retroflexus cells to atrazine in comparison with those of several other plant species to understand what causes this differentially inter-specific response. Atrazine scarcely inhibited the cell growth of either atrazine-resistant and susceptible-Amaranthus cells. Tobacco cells, however, could not grow as cultured Amaranthus cells in high concentrations of atrazine even under heterotrophic culture conditions. Atrazine-resistant tobacco cells were also sensitive to high concentrations of atrazine. The inhibition of cell growth by this secondary effect of atrazine was also observed in cultured wheat and rice cells. Atrazine-sensitive Chenopodium cells are relatively more resistant to high concentrations of atrazine. The importance of potential tolerance to the secondary effects of atrazine is discussed with respect to the frequent occurrence of triazine- resistant biotypes in limited plant species.