Estimation of some parameters associated with nitrogen accumulation and remobilization in spring bread wheat cultivars

Quantitative information of nitrogen accumulation and remobilization under varying environmental and growing conditions are limited for wheat (Triticum aestivum L.) cultivars in Golestan province of Iran. This information is used for quantifying nitrogen partitioning between leaves and stems during vegetative stage and the remobilization to the grains during reproductive stage. This experiment was carried out at research farm of the Gorgan University of Agricultural Sciences and Natural Resources، Gorgan، Iran، in 2005-2006 using randomized complete block design with four replications. The experiment was conducted with four spring bread wheat cultivars t (Kohdasht، Shiroudi، Tajan and Zagross) in three planting dates (14 Dec.، 20 Jan. and 20 Feb.). Results revealed that N concentration (%) in leaves was 5% up to beginning of grain growth stage، and then declined linearly to 2% at physiological maturity. Stem N% decreased from 2. 3% at anthesis to 1. 7% in senesced stems at maturity. Results indicated that a positive relationship exists between nitrogen content of grain and whole plant، as each unit increase in the whole plant nitrogen (%) increased grain nitrogen content by 0. 89%. This relationship can be used to estimate grain nitrogen content. Nitrogen partitioning in vegetative stage was 58% to stems and 42% to leaves. Those cultivars that had greater remobilization efficiency from stem reserves in reproductive stage، also had higher grain nitrogen content. A significant relationship was observed between nitrogen remobilization and nitrogen content of vegetative organs at maturity stage that can be used to predict nitrogen remobilization. It was found that nitrogen remobilization decreased by 25. 4% per each unit increase in nitrogen content in vegetative organs. The parameter estimates and functions obtained in this study could be used to simulate N accumulation and remobilization for spring bread wheat cultivars.