ASSIMILATION AND REMOBILIZATION OF NITROGEN AND CARBOHYDRATES IN OATS, ESPECIALLY AS RELATED TO GROAT PROTEIN CONCENTRATION

Abstract

Experiments with field-grown oats (Avena sativa L.) were conducted to determine (1) the relationships between assimilation and remobilization of N and carbohydrates and the groat protein concentration, (2) the carbohydrate composition of plant parts at anthesis and maturity, and (3) the contribution to the grain of N and carbohydrates assimilated before anthesis, as compared to post-anthesis assimilates. Six cultivars, varying in groat protein concentration, were harvested at intervals throughout development until maturity. Total shoot assimilation of N, on either a plant or land-area basis, was unrelated to groat protein concentration. However, the relative ability of the cultivars to remobilize N out of leaf and culm tissues into the panicle was correlated with groat protein concentration. Starch (plus total sugars) comprised most of the total nonstructural carbohydrates of all shoot parts. Fructosans, which were low at anthesis, declined to maturity. Net losses of N from leaf and culm tissue between anthesis and maturity accounted for 27–47% of the gain in panicle N during this interval. For total nonstructural carbohydrates, leaf and culm net loss was 15–24% of panicle gain in total nonstructural carbohydrates. Thus, the majority of panicle N and carbohydrate was derived from assimilation of N and CO2 after anthesis.