Some Biochemical Effects of Glyphosate on Plant Meristems

Glyphosate promoted the activity of phenylalanine ammonia lyase (PAL) in both single node rhizome buds of Agropyron repens and root tips of wheat seedlings, in the latter case correlating inversely with decline in respiratory activity. Differential rates of 14C-amino acid incorporation suggest that glyphosate depleted the phenylalanine protein precursor pool with resultant inhibition of protein synthesis, as evidenced by a rapid decline in the level of ‘soluble’ protein. Promotion of PAL is assumed to occur by derepression through decline in end-product levels. Activities of shikimate: NADP oxidoreductase (SORase), chorismate mutase, and polyphenol oxidase (PPO) were also elevated, but to lesser extents than for PAL.