Effect of levels of nitrogen on growth, nitrogen uptake patterns and grain protein fractions of sorghum

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The effect of levels of nitrogen on growth and nitrogen uptake patterns and grain protein quality of grain sorghum was investigated by two experiments which were conducted at Pakdasht-Tehran in 2003. In a completely randomized design with three replications, grain sorghum (Sorghum bicolor (L.) Moench) hybrid H-726 was grown under greenhouse conditions using water culture technique. The first experiment included a standard culture solution with 88 ppm nitrogen level and the second experiment consisted of various nitrogen levels (17.5, 44, 88, 220 and 440 ppm) in culture solution. The total fresh weight of plant and nitrogen uptake pattern increased linearly until plants reached the hard dough stage and then decreased. Sorghum plant had two peaks of absorbing nitrogen in vegetative and in reproductive period of growth (four weeks before and after heading stage). Fresh weight, dry matter of plant, grain yield and crude starch decreased significantly and total nitrogen content in the plant parts, nitrogen uptake, crude protein and prolamin increased significantly by increment of nitrogen application. The major protein in grain constituted of glutelin followed by prolamin at any level of applied nitrogen. Effect of different levels of nitrogen was not significant on crude fat and crude ash of grain. The significant positive correlation coefficient of albumin with globulin and glutelin with total extractable protein were the highest (r = 0.99). The correlation between crude protein and grain dry matterwas negative and high (r = -0.73).

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