INFLUENCE OF DROUGHT ON THE CONCENTRATION AND DISTRIBUTION OF 2,4-DIAMINOBUTYRIC ACID AND OTHER FREE AMINO-ACIDS IN TISSUES OF FLATPEA (LATHYRUS-SYLVESTRIS L)

2,4-Diaminobutyric acid (A2bu) may be responsible for the apparent toxicity of flatpea (Lathyrus sylvestris L.) forage to some livestock. To obtain information relative to environmental regulation of A2bu, 3-month old flatpea plants, cv. "Lathco", were subjected to water-deficit stress for 1, 2, and 4 weeks. A2bu, the most abundant free amino acid in roots, stems, and leaves, increased nearly 100% in roots of stressed plants. Increases in the concentrations of asparagine (Asn), proline (Pro), and arginine (Arg) occurred in roots; Asn, Pro, and 4-aminobutyric acid (Abu) in stems; and Pro and homoserine (Hse) in leaves also occurred in response to drought stress. Proline was a minor constituent of the free amino acid pool, even under water-deficit stress. The distribution of A2bu and Pro in the stressed plants (roots > stems > leaves) was the reverse of that in plants supplied with adequate water (roots < stems < leaves). As concentrations of Asn and Abu decreased from roots to leaves in control tissues, concentrations of Hse and A2bu increased in roughly the same proportions. This observation suggests that Abu and Asn may be precursors of A2bu and Hse, respectively. The increase in A2bu levels in aerial parts of drought-stressed flatpea plants is probably not sufficient to lower the feed value of the forage. © 1990.