Effects of nitrogen fertilizers on wheat photosynthetic pigment and carbohydrate contents

Abstract

The effect of nitrogen fertilizers on the physiological indices of winter wheat (Triticum aestivum L. variety ‘Ada’) was investigated in experimental fields of the Lithuanian University of Agriculture in 2005–2006. The rates of fertilizers during plant vegetation were as follows: N90, N150 and N180. In sowing time, wheat was fertilized with N30P80K120. In tillering stage, plants were fed with calcium-ammonium nitrate N60 and N80. In booting stage, they were fertilized through leaves with carbamate solution N30 and N40. Wheat organogenesis stage, photosynthetic pigment and carbohydrate contents were determined. According to our results, plants respond to nitrogen supply differently during separate phenological phases. Supplementary fertilization accelerated plant development only at lower applied concentrations (N150) and developmental differences showed up only in booting stage. The best development was related with a high chlorophyll a / b ratio and a low carbohydrate content. Total photosynthetic pigment contents increased with plant age and were higher at higher fertilization rates. Chlorophyll a, b and carotenoid biosynthesis showed similar responses to N fertilization. The increase in photosynthetic pigment contents coheres with a decreased fructose accumulation and an enhanced disugar (sucrose and maltose) synthesis intensity during wheat growth. The results confirm the potentiality to control wheat physiological indices by using different nitrogen fertilization designs. Keywords: nitrogen fertilizers, carbohydrates, photosynthetic pigments, winter wheat