Nonprotein amino acid composition of flatpea (Lathyrus sylvestris L.) as affected by ethephon seed treatments and seedling fertilization

Use of flatpea (Lathyrus sylvestris L.) as a forage is limited because of nonuniform seed germination and the potentially toxic effects of 2,4-diaminobutyric acid (A₂bu), a nonprotein amino acid found in seeds and vegetative tissues. The effects of ethephon (2-chloroethyl phosphonic acid) on seed germination, amino acid leachates of seeds, and amino acid composition (particularly A₂bu) of seedlings were investigated. Germination of flatpea seeds, imbibed for 16 h in 0, 100, 200, 400, 800, and 1600 mg/L ethephon, did not differ, but amino acid leachates tended to increase up to 200 mg/L ethephon and then decline at higher concentrations. The major amino acid constituents in leachates were A₂bu, 4-aminobutyric acid (Abu), and homoserine (Hse). Dry matter accumulation of seedlings grown from ethephon-treated seeds was reduced for second cuttings grown from ethephon-treated seeds and high nitrogen grown plants. During regrowth, free amino acid accumulation was most pronounced in leaves of plants supplied with high nitrogen. The most abundant free amino acids in flatpea tissues were the same as those in seed leachates, but concentration and relative abundance varied with nitrogen level, plant part, and ethephon treatment. Results suggest that ethephon seed treatments can have persistent effects on the growth and amino acid composition of flatpea seedlings grown under different nitrogen regimes.