The effect of differential nitrogen fertilization on photosynthetic pigment and carbohydrate contents in the two winter wheat varieties

Abstract

The effect of nitrogen fertilizers on photosynthetic indices in two winter wheat (Triticum aestivum L.) varieties ‘Ada’ and ‘Seda’ was investigated in the experimental station of Lithuanian University of Agriculture during 2005–2006 and 2006–2007. The rates of fertilizers during wheat vegetation were as follows: N90, N120 and N150. In sowing time both varieties were fertilized with N30P80K120. In tillering stage plants were fed with calciumammonium nitrate N60 and N80. In stem elongation stage they were fertilized through leaves with carbamide solution N30 and N40. Wheat photosynthetic pigment and carbohydrate contents were determined in flowering and seed growth stages. The results of analysis show that photosynthetic pigment and carbohydrate status are suitable indicators of the activity of the winter wheat photosynthetic system. Suitably selected nitrogen fertilization design may delay the natural senescence processes. However, the emergence of the indices of senescence is also dependent on environmental conditions. Nitrogen remobilization and photosynthetic activity during natural senescence is cultivar specific. The photosynthetic system of ‘Ada’ wheat variety is more sensitive to the evocative factors than ‘Seda’ wheat. The soluble sugars also participate in senescence launching: the lower hexoses/sucrose ratio corresponds to decline in photosynthetic pigment degradation. Earlier photosynthetic senescence corresponds to reduced wheat grain yields.