The Relation between Fertilization Practices and Functional Metabolites of Crops: A Review

Various researches on the effects of fertilization levels on functional metabolites in crop have been conducted. This review summarizes the previous studies on the relation between fertilization supply and accumulation of metabolites (phenolics, carotenoids, ascorbic acid and glucosinolates) which function as antioxidants in crop. The accumulation of phenolic compounds is related to the activation of phenylalanine ammonia lyase (PAL) in phenylpropanoid pathway. Most of the previous studies discuss that low nitrogen (N) supply activates PAL, thereby increasing the synthesis of phenolics. Similarly, high N supply leads to a decrease in ascorbic acid because of the shading effect derived from the accelerated vegetative growth under high N level. Unlike the phenolics and ascorbic acid, carotenoids are accumulated with increasing N supply. In this regard, the previous studies explain that N is a main element closely associated with formation of key enzyme for the synthesis of carotenoids. Glucosinolates are generally increased under decreasing N supply and increasing S supply. Although the previous studies show similar trends about the accumulation of metabolites by nutrient level, they also suggest that many other factors including crop types, cultivars, cultural environment (water, temperature, light, etc.) influence the accumulation of functional metabolites in crop.