The aim of the study was to evaluate the effects of drought stress and timing of nitrogen (N) application on nitrogen remobilization, bread-making quality indices of grain protein and Zeleny Sedimentation (ZS), as well as trend of storage protein expression during grain filling in bread wheat (triticum aestivum var Mahdavi). A field trial was conducted at Research Station of Agricultural Collage, Karaj in 2000-200 1. A split plot design based on RCB with four replicates was employed. Soil moisture regime (SMR) was considered as main plot, including control (C) while drought stress (5) conditions, as well as timing of N application, as sub plots. Nitrogen applications included: no nitrogen (N0), 120 Kg N/ha applied as 20% + 80% (N1), and 40% + 6O°/o (N2) at sowing and flowering stages respectively. The effect of N treatment on nitrogen remobilization was significant. The highest and lowest nitrogen remobilization was observed in N1 and N0 treatments respectively. Drought stress increased grain protein percentage and Zeleny sedimentation. Interaction between SMR and nitrogen treatment on grain protein percentage and ZS was also significant; grain protein percentage and ZS of N0 and N2 treatments in control condition were completely different from those in stress condition. Grain protein percentage in N1 treatment was approximately similar in either stress or control conditions. The highest and lowest amount of ZS was observed in SN2 and CN0 treatments respectively. The highest grain protein percentage belonged to SN2 treatment. Correlation between grain protein percentage and ZS was significantly positive under both conditions. Storage proteins in grain were investigated through electrophoresis technique (SDS-PAGE) at milky, doughy and maturity stages. There was no noticeable difference observed between polypeptide bands of different treatments at milky and doughy stages. However at maturity, CN0 and SN0 treatments demonstrated similar extra polypeptide band, not observed in other treatments.
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