Effects of Glyphosate on Metabolism of Phenolic Compounds

Abstract

Light enhanced the inhibiting effect of root-fed glyphosate (5 x l'0~* M) on dry weight accumulation of soybean [Glycine max, (L.) Merr.l seedling axes. Inhibition of growth by iight 'was greatest in hypocotyls, whereas by glyphosate it was greatest in roots. A synergistic effect of light and glyphosate on stimulation of phenylalanine ammonia-lyase (PAL, B.C. 4.3.1.5) activity was also demonstrated. In continuous white light PAL activity increased linearly for 4 days in axes of seedlings exposed to glyphosate. Evidence of phytochrome involvement in the light effect was shown. The stimulatory effect of glyphosate on PAL activity was greater in roots than in hypocotyls., Solable hydroxyphenolic compound levels were reduced by glyphosate bot were increased by light on a per axis basis. On a fresh weight basis, hydroxyphenolics were more concentrated in glyphosate-treated than in control tissues in the light. When compared to other amino acids, disproportionate decreases in free pools of phenylalanine and tyrosine occorred in axes of seedlings treated with giyphosate and iight. The effect of light on all measured parameters was mainly in the hypocotyl, while that of glyphosate was primarily in the root. In the light, glyphosate caused increases in levels of giutamine and other amino acids that may be the result of amination reactions, protecting from excess ammonia ,generated by enhanced PAL activity. These results suggest that PAL has a strong influence on its substrate levels in this system and/or that glyphosate inhibits synthesis of aromatic amino acids. 0031-9317/79/080307-11 S03.00/0

Nitrogen Metabolism and Flower Symmetry of Petunia Corollas Treated with Glyphosate

“…This inhibition led to decreased levels of aromatic amino acids that subsequently cause an inhibition of protein synthesis Rubin et al, 1984). In addition, glyphosate induced high levels of PAL activity (Duke et al, 1979(Duke et al, , 1980Cooley and Foy, 1992;Amrhein and Gödeke, 1977). High levels of PAL activity produced toxic levels of ammonia and increased the levels of growth-inhibiting phenolic compounds (Duke et al, 1980).…”

“…Control (mol%) Glyphosate (mol%) important precursor in the production of IAA (Hoagland et al, 1978;Duke et al, 1979). Thus, the effect of glyphosate on aromatic amino acid metabolism was the next examination.…”

“…Glyphosate caused a reduction of anthocyanin formation and PAL activity (Shimada and Kimura, 2006) but did not affect the aromatic amino acid and protein biosynthesis. Phenylalanine and tyrosine are the important precursors in the production of phenolic compounds and lignin (Duke et al, 1979). Tryptophan is an Table I.…”

“…There have been reports on effects of glyphosate on the amino acid metabolism using axes of soybeans [Glycine max (L.) Merr.] (Duke et al, 1979(Duke et al, , 1980 and maize (Zea mays L.) (Hoagland et al, 1978), suspension-cultured cells of carrot (Daucus carota L.) and tobacco (Nicotiana tabacum L.) (Haderlie et al, 1977), rhizome buds of quackgrass [Elytrigia repens (L.) Nevski], roots of wheat (Triticum aestivum L.) (Cole et al, 1980), inflated duckweed (Lemna gibba L.) (Cooley and Foy, 1992). However, there is not any information on effects of glyphosate on the amino acid metabolism using floral organs.…”

Reversal of Glyphosate Inhibition of Carrot Cell Culture Growth by Glycolytic Intermediates and Organic and Amino Acids

“…Gresshoff (12) reported reversal of glyphosate inhibition of Arabidopsis thaliana seedlings with a combination of phenylalanine and tyrosine. In contrast, Duke and Hoagland (6) observed increased inhibition by glyphosate of corn seedling growth when phenylanine and tyrosine were added.Several studies (7,8,16) show that glyphosate treatment can decrease free phenylalanine and tyrosine levels. Recent studies have indicated that glyphosate inhibits the synthesis of flavonoids and chlorogenic acid in buckwheat hypocotyls (17) and causes an accumulation of shikimate that is significantly correlated with a…”