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Inhibition of Corn, Soybean, and Wheat Seedling Growth by Amino Acid Analogs¹

The inhibitory effects of the amino acid analogs DL-5-methyltryptophan (5MT, tryptophan analog), S(2-aminoethyl)-L-cysteine (AEC, lysine analog), L-ethionine (Eth, methionine analog), and DL-methionine-DL-sulfoximine (MS, methionine analog) on the growth of corn (Zea mays), soybean (Glycine max), and wheat (Triticum aestivum) seedlings were determined when the compounds were supplied in the nutrient solution. Twenty ppm 5MT, 20 ppm Eth, or 50 ppm AEC inhibited seedling growth; this inhibition could be reversed by 350 ppm L-tryptophan, 150 ppm L-methionine, or 240 ppm L-lysine, respectively. The growth inhibition caused by 5MT was specifically reversed by the corresponding natural amino acid.

Ethylmethane sulfonate-treated seeds were allowed to growth to maturity and the seeds collected. The screening of 100,000 wheat seedlings (M₂) in inhibitory 5MT concentrations (20 ppm) has resulted in the recovery of 5 plants resistant to this analog. These plants are being studied further.

Growing wheat plants to maturity in nutrient solution containing 2.5 mM L-tryptophan, resulted in a 13- fold increase in free tryptophan in the mature seed.

Key Words: Zea mays L. • Glycine max (L.) Merrill • Triticum aestivum L. • feedback inhibition • amino acid analogs • amino acids

² Graduate student (on leave from: Department of Agronomy, G. B. Pant University of Agriculture and Technology, Pantnagar, India) and associate professor of plant physiology, respectively, Department of Agronomy, University of Illinois, Urbana, IL 61801.

Received for publication May 18, 1974.