Effects of herbicides on the concentration of poisonous compounds in plants: a review.

Herbicides may raise, lower, or not affect the concentration of poisonous compounds in plants. Herbicides, 2,4,5-T and silvex controlled Wasatch milkvetch (Astragalus miser var oblongifolius) and markedly reduced the concentration of miserotoxin, a poisonous aliphatic nitro compound. The concentration of phototoxic furocoumarins in the leaves of spring parsley (Cymopterus watsonii) decreased to nontoxic concentrations 4 to 5 weeks after treatment with 2,4-D. The hydrocyanic acid content of wild cherry (Prunus spp) decreased after treatment with 2,4-D and 2,4,5-T, but increased in Sudangrass (Sorghum halapense) after treatment with 2,4-D. The alkaloid concentration in Barbey larkspur (Delphinium barbeyi) increased after treatment with 2,4,5-T or silvex, decreased in horsetail (Equisetum palustre) after treatment with MCPA, and was unaffected in Datura after treatment with several herbicides. The effect of herbicides on nitrate concentration in plants was dependent upon the species of plant and the herbicide used.