The impact of atmospheric temperature and soil nitrogen on some physiological traits and dry matter accumulation of wheat (Triticum aestivum cv. Bahar)

Wheat is the most important cereal crop in the world as well as in Iran. The studies related to the effects of global climate change on wheat production usually assess the impact of changes in atmospheric CO2 concentration and temperature on growth and yield. On the other hand, nitrogen is the most crucial plant nutrient for crop production and the proper management and improving the utilization efficiency of nitrogen fertilizers is very important. The greenhouse experiments were, therefore, conducted to assess concomitant effects of temperature and nitrogen supply on the growth and some physiological traits of Bahar bread wheat cultivar. In this experiment effects of four nitrogen levels (0, 50, 100 and 150 mg kg-1 from ammonium nitrate source, N=35%) at two environments, one with an ambient temperature of 25 ± 3°C and the other with an elevated temperature of 35 ± 3°C were tested on the wheat genotype in a completely randomized design with three replications. The results were suggestive of decreases in all measured traits with increasing temperature, except shoot nitrogen concentration. Elevated temperature reduced the shoot dry weight of plant at levels of 0, 50, 100 and 150 mg kg-1 of nitrogen fertilizer by 1.16 g or 50%, 0.47 g or 21%, 0.45 g or 16% and 0.81 g or 26%, respectively. The maximum shoot dry matter belonged to 150 mg kg-1 of nitrogen fertilizer at ambient temperature and 100 mg kg-1 of soil nitrogen fertilizer at the elevated temperature. It seems that rising temperatures will reduce the nitrogen use efficiency at the heading stage of wheat.