Selectivity of Linuron on Tomato and Parsnip

Abstract
In a study of the selective action of 3-(3,4-dichlorophenyl)-l-methoxy-l-methylurea (linuron), parsnip (Pastinaca saliva L., var. Harris Model) possessed a high degree of tolerance as compared to tomato (Lycopersicum esculentum Mill., var. Kokomo). Linuron was readily taken up by the roots of tomato and distributed throughout the plant, but it remained mostly in the roots of parsnip. Linuron in the leaves of parsnip was metabolized, to a great extent, while very little of the metabolite (s) was found in tomato. The herbicide caused rapid and complete inhibition of photosynthesis in tomato, and the plants never recovered. Photosynthesis in parsnip was inhibited but only temporarily. Therefore, it appears that the selectivity of linuron on these two species may be explained by the two mechanisms of differential accumulation in the foliage and metabolism of the herbicide.