Morphological and Anatomical Effects of Mefenacet on the Growth of Barnyardgrass(Echinochloa oryzicola Vasing.).

Abstract

Morphological and anatomical effects of mef enacet on the growth of barnyardgrass (Echinochloa oryzicola Vasing.) were investigated in petri-dish and pot tests. In the petri-dish, mef enacet did not inhibit weed germination. After germination, however, leaves failed to emerge through the coleoptile, and the primary root was reduced at high concentrations, 10 and 5 ppm. At low concentrations, 0.5 and 0.1 ppm, the growth of shoot, root and coleoptile was slightly inhibited, while the mesocotyl was not affected by the herbicide. In the preemergence treatment in pots, mef enacet did not inhibit the elongation of mesocotyl or coleoptile, however, it severely retarded the growth of 1st and 2nd leaf primordia and length of the primary root. When the weed was treated at 1, 2 and 3 leaf stages, the growth of primordia of subsequent leaves was retarded, and the elongation of coronal roots was inhibited. Anatomical results showed that mefenacet clearly exerted a strong inhibitory action against meristems, but had little effect on existing plant tissue. When applied at the 2-leaf stage, the growth of subsequent leaves was strongly retarded, as was the leaf sheath of the 3rd leaf. The upward and marginal growth of the 3rd and 4th leaves was inhibited and the growth of primordia of the 5th and 6th leaves was also severely inhibited. The growth of epidermal cell was affected and the intercellular spaces of the mesophyll did not form extensive lacunae as shown in the untreated plant. At the 3-leaf stage application, the growth of primordia of the 4th, 5th and 6th leaves was retarded and abnormal swelling of the 1st, 2nd and 3rd tillers was observed.

Effect of fentrazamide on the growth, morphology and anatomy of Echinochloa crus-galli and Echinochloa oryzicola

“…Microscopic observation on meristematic tissues of both Echinochloa species treated with fentrazamide and mefenacet provided some common results: i) depressed internodial growth; ii) inhibited nor- mal foliation at the main stem and axial buds; iii) inhibition of cell elongation in the longitudinal direction; iv) the inhibition of the differentiation and growth of roots and lateral buds; v) deep staining of the nuclei of leaves, lateral buds, procambium, vascular tissue and root primordial. We previously reported macroscopic and anatomic symptoms of E. oryzicola caused by mefenacet treatment, 11) which were similar to those caused by fentrazamide in this paper. Hess et al showed that mefenacet inhibited both cell division and cell enlargement with Clamydomonas reinardtii and A. sativa.…”

“…Microscopic observation of cross sections treated with fentrazamide in this paper was similar to those of metolachlor 7) and butachlor. 14) Although chloroacetamides and oxyacetamides were described as inhibitors of both cell division and cell enlargement, 11,15) a recent study revealed that chloroacetamides like thenylchlor, 2-chloro-N-(2-ethyl-6-methylphenyl)-N-[(1-methylethoxy)methyl]acetamide 6) and chloroacetanilides including pretilachlor, 7) inhibited the biosynthesis of very long chain fatty acids (VLCFAs) as well as oxyacetamides, including mefenacet 8) and cafenstrole, N,N-diethyl-3-(2,4,6-trimethylphenyl)sulfonyl-1H-1,2,4-triazol-1-carboxamide). 8) Physiological and biochemical studies have shown that fentrazamide inhibited the formation of VLCFAs, similar to chloroacetamides and chloroacetanilides.…”

“…10) Anatomical results showed that mefenacet inhibited the upward growth of subsequent leaves, and the differentiation and growth of crown roots and lateral buds. 11) In this study, morphological and anatomical effects of fentrazamide on the growth of E. crus-galli and E. oryzicola were compared with those of mefenacet.…”

Action of fentrazamide on protein metabolism and cell division in plants

“…The mode of action of fentrazamide has been considered the inhibition of cell division 4,5) or fatty acid elongation. [6][7][8] We examined the change of soluble amino acid composition in fentrazamide, cafenstrole or mefenacet-treated early watergrass and rice, because herbicides with the same mode of action show a similar pattern of changes in amino acid composition.…”

“…4) Reductions in the length of young leaves, the number and length of coronal roots, leaf sheaths and leaf blades were also reported. 5) Some physiological and biochemical studies reported that fentrazamide inhibited the formation of very long chain fatty acids (VLCFAs), similar to chloroacetamides and chloroacetanilides. The incorporation of [ 14 C]-oleic acid into sporopollenin, which mainly consists of VLCFA in a green alga Scenedesmus acutus, was sensitive to 0.1 to 1 mM of fentrazamide, similarly to chloroacetanilides which inhibit fatty acid modification.…”