Effects of Seed and Root Lipids on the Susceptibility of Plants to Trifluralin and Oryzalin

Abstract

Extensive variability in total lipid composition was observed in seeds of different plant species as well as cultivars within the same species. Susceptibility of plants to soil-incorporated trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine) and oryzalin (3,5-dinitro-N4,N4-dipropyisulfanilamide) under greenhouse conditions decreased as the percentage of total lipid in dry seeds increased. Species with high seed lipid levels such as jimsonweed (Datura stramoniumL.), soybean [Glycine max(L.) Merr.], and velvetleaf (Abutilon theophrastiMedic.) were less susceptible to these herbicides than were oat [Avena sativa(L.), giant foxtail (Setaria faberiHerrm.), and sorghum [Sorghum bicolor(L.) Moench.] with low seed lipid levels. Velvetleaf was the most tolerant to the herbicides. Corn (Zea maysL.) cultivars with a wide range of seed lipid content (4.45 to 17.0% of dry weight) were germinated in herbicide-free soil, but their roots were allowed to grow through trifluralin- or oryzalin-treated soil. Roots of seedlings from seeds with high lipid content had higher lipid contents than those from low-lipid seeds. There was a significant correlation between root lipid content and sensitivity to trifluralin or oryzalin. Roots high in lipids were less susceptible than those with low amounts of lipids. Similar results were obtained for oat cultivars. The fatty acid composition of plant roots differed among plant species and also among cultivars of the same species. The individual fatty acids did not significantly correlate with susceptibility of roots to trifluralin or oryzalin. Root lipid and fatty acid compositions were not significantly altered by trifluralin or oryzalin treatment.