Effects of nitrogen fertilizer on protein synthesis, accumulation, and physicochemical properties in common buckwheat

Abstract

Nitrogen (N) fertilization affects grain quality in common buckwheat (Fagopyrum esculentum Moench). But the effects of N fertilizer on various buckwheat protein parameters are not fully understood. This study aimed to investigate the synthesis, accumulation, and quality of buckwheat protein under four N application rates in the Loess Plateau, China. Optimal N application (180 kg N ha−1) improved yield, agronomic traits, and N transport and increased protein yield and protein component accumulation. Prolamin and glutelin accumulation first increased and then decreased with increasing N application. The relationships between the contents of protein components and the amount of applied N generally followed quadratic functions. Nitrate reductase and glutamine synthetase activities first increased and then decreased with increasing N levels. Optimal N fertilizer increased the waterholding capacity and thermal stability of buckwheat protein and reduced its emulsification capacity, but negligibly changed its oil-absorption capacity. Hydrophobic amino acids and glutelin content were the main factors affecting protein quality.