Ecological fitness of Senecio vulgaris and Amaranthus retroflexus biotypes susceptible or resistant to atrazine.
Atrazine-resistant or -susceptible biotypes of Senecio vulgaris and Amaranthus retroflexus were compared with regard to DM production, resource allocation and competitive ability. DM production of susceptible biotypes was greater than that of resistant biotypes under both competitive and non-competitive conditions. Resource allocation patterns were similar for both biotypes of each species. Susceptible biotypes of S. vulgaris and A. retroflexus were more competitive than resistant biotypes under all the conditions tested.