Amino-acid composition and protein and carbohydrate accumulation in the grain of triticale grown under terminal water stress simulated by a senescing agent

Two field experiments involving two triticale genotypes and the application of a senescing agent (KI) to stimulate the effect of a terminal drought stress were conducted at two sites during 1996. Although protein did not differ between genotypes, significant differences were found in methionine and lysine. The percentage of amino acids in the grain increased linearly with grain-protein content, this relationship being non-linear in the same degree for all amino acids. An inverse relationship (r(2) = 0.803) was found between the rates of carbohydrate and protein accumulation in absence of the senescing agent, indicating competition in the transport of proteins and carbohydrates to the grain. Terminal drought stress induced by KI application increased the amino-acid concentration in the grain, mainly due to a higher protein content. Nevertheless, the amino-acid composition of the protein did not change after this application. The senescing agent, significantly reduced dry weight as well as carbohydrate- and protein-accumulation rates in the grain, thus forcing the grain to be filled with carbohydrates assimilated before anthesis. Therefore, the grain-carbohydrate accumulation rate appeared highly dependent (r(2) = 0.884) of the quantity of nonstructural carbohydrates available for studying protein and carbohydrate accumulation in small-grain cereals. (C) 2000 Academic Press.