Influence of nitrate and ammonium on the growth and 2,4‐diaminobutyric acid composition of flatpea (Lathyrus sylvestris L.)

Abstract

Abstract. Presence of 2.4‐diaminobutyric acid (A2bu), a neurotoxin, in tissues of flatpea (Lathyrus sylvestris L.) necessitates a thorough understanding of the regulation of this nonprotein amino acid before the species can be recommended to livestock producers for forage applications. To determine how different concentrations and ratios of NO3 and NH+4 in growth media influence the levels of A2bu and other free amino acids in the ‘Lathco’flatpea cultivar, plants were grown hydroponically in controlled environments. The concentration of A2bu was highest in tissues when the NO3 to NH+4 ratio in the nutrient solution was low. Responses of amides and other nonprotein amino acids, especially in the roots, followed a similar trend. Free protein amino acids in leaves and stems were generally unaffected by changes in NO3 to NH+4 ratios. In roots, protein amino acids increased as the NO3 to NH+4 ratio in the growth medium increased. Ammonium inhibited shoot and root growth; NO3 alleviated the toxic effects of NH+4. Soluble protein concentrations were higher in the shoots of NO3‐fed plants and in the roots of plants supplied with NH+4. These results suggest that accumulation of A2bu and other nonprotein amino acids, as well as asparagine and glutamine, plays a role in detoxification of NH+4 and storage of N.