Effects of Metolachlor on Germination, Growth, Leucine Uptake, and Protein Synthesis

Abstract

The effect of metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide] on the germination and growth of 14 plant species was investigated. A 10-3M concentration of the herbicide did not reduce germination as much as 10% for corn (Zea maysL. ‘Pioneer 3369A’), English pea (Pisum sativumL. ‘Thomas Laxton’), sicklepod (Cassia obtusifoliaL.), or wheat (Triticum aestivumL. ‘Coker 68–15′) but reduced germination of oat (Avena sativaL. ‘Coker 227′) to 0, lettuce (Lactuca sativaL. ‘Grand Rapids’) to 11%, and peanut (Arachis hypogaeaL. ‘Florunner’) to 14%. A 10-6M concentration did not affect the germination of any species tested. A 10-5M concentration did not significantly decrease length or fresh weight of corn, morningglory, or wheat roots but had at least some adverse effect on all other species tested. At this concentration root length was less than 2/3 of the control for English pea, cucumber (Cucumis sativusL. ‘Ashley’), radish (Raphanus sativusL. ‘Scarlet Globe’), sicklepod, and soybean [Glycine max(L.) Merr. ‘Ransom’]. Metolachlor was supplied to germinating seeds of barley (Hordeum vulgareL. ‘Barsoy’), English pea, and corn either only in the shoot, seed, or root zone, or to all parts. One kg/ha applied in the shoot zone of barley and corn significantly reduced seedling height and dry weight but had no effect when applied in either the seed or root zone. Application in all zones was approximately twice as detrimental as when applied in only the shoot zone. Application of 4 kg/ha in only the shoot, seed, or root zones of English pea did not decrease seedling height or dry weight but application in all zones decreased these values about 98%. A 10-5M concentration of metolachlor decreased leucine uptake by cucumber root tips but not its incorporation into protein. A 10-4M concentration strongly reduced leucine uptake and slightly decreased leucine incorporation into protein.