Free radical scavengers and inhibitors of lipoxygenases as antagonists against the herbicides haloxyfop and alloxydim
1993
Banas, A. | Johansson, I. | Stenlid, G. | Stymne, S. (Sveriges Lantbruksuniv., Uppsala (Sweden). Inst. foer Vaextfysiologi)
The growth of wheat seedling roots during 24 h treatment in nutrient solution was inhibited to 50% by 10-7 M haloxyfop or 4. 10 10-7 M alloxydim. The total amount of fatty acids in the meristematic root tips was reduced by these concentrations to ca 85% of the control and the quotient 18:3/[18:1+18:2] was changed from 0.8 in the control to 1.5-2.5 in the treated plants. In the whole root the increase of the fatty acid content during 24 h was reduced to 34% of that in the control by the addition of 10-7 M haloxyfop. The effect of these herbicides in wheat roots was counteracted by several substances, such as flavonoids, pyridazinone herbicides, salicylic acid, dihydroguaiaretic acid, salicylhydroxamic acid, propyl gallate, monophenylbutazone and diphenylamine. A common feature of most of these substances is that they can act as scavengers of free radicals and inhibitors of lipoxygenases. Inhibition of the growth with cerulenin was accompanied by similar changes of the fatty acids as found after treatment with the grass herbicides. However, the inhibition caused by cerulenin was not reversed by the above-mentioned antagonists. Treatment with haloxyfop led to an increased liberation of ethylene from meristematic parts of young oat shoots 18 h after the application. In wheat root tips the activity of lipoxygenases also was increased after about 18 h. It is suggested that at least part of the specific inhibition caused by these grass herbicides is due to an increase of the relative amounts of polyunsaturated fatty acids and to increased oxidation of these acids resulting in inhibitory products such as free radicals and ethylene.
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