EFFECT OF MOLYBDENUM APPLICATIONS ON CONCENTRATIONS OF FREE AMINO ACIDS IN WINTER WHEAT AT DIFFERENT GROWTH STAGES

Abstract

ABSTRACT A pot experiment with winter wheat was conducted on a yellow- brown acid soil collected from Xinzhou, Hubei Province, China. The free- and protein-amino acid concentrations in leaves of control and molybdenum (Mo)-treated winter wheat were determined at tillering, elongation, and the ear sprouting stages. Under low nitrogen (N) conditions, the free amino acid, free alanine, and glycine concentrations in winter wheat leaves at tillering and elongation stage were increased by Mo application, suggesting that N metabolism during the vegetative growth period of winter wheat was improved by Mo application. However, the free amino acid concentration of Mo-treated plants was reduced significantly at the ear sprouting stage, indicating that the Mo treated wheat was retarded by earlier N deficiency. Under high N conditions, the total free amino acid concentration of winter wheat leaves was increased at tillering, but was decreased considerably at the ear sprouting stage by applying Mo. Thus, Mo fertilizer accelerated the amino acid synthesis of winter wheat at tillering, while the N metabolism of Mo deficient wheat at the generative stage was extremely vigorous. The free glutamic acid concentration was decreased, and the free alanine, glycine, and aspartic acid concentrations were increased by Mo application, at the high N application rate. High free glutamic acid and serine concentrations in wheat were induced by Mo deficiency. Thus the transformation of glutamic acid might be handicapped under Mo deficient conditions. The sulphur-containing amino acids and the concentrations of phenylalanine, tyrosine were all increased at the elongation stage while Mo was utilized.