| The experiment was conducted on the research farm of Shandong Agriculture University, Taian, Shandong Province, P. R. China. Two winter wheat (Jriticum aestivum L.) cultivars, YN15 and JM19, were used to study the effect of nitrogen on noodle-making quality of winter wheat, and its physiological and biochemical basis. The main results are as follows.1. Effect of nitrogen on noodle-making quality and flour quality: Nitrogen fertilization improved noodle-making quality and flour quality of winter wheat. There is a significantly positive correlation between nitrogen fertilization and noodle total score (with fresh-noodle is 0.763*, with dry-noodle is 0.721*, and with two sorts of noodle is 0.733*). The same relation was detected between nitrogen fertilization and noodle's color, apparent and flexibility, while no obvious effect on noodle's tastes and smooth were found. As to flour quality, nitrogen fertilization added protein content of grain, gluten content of flour, developing time, stability time and SDS sedimentation value, while decreased extension. Nitrogen fertilization also increased ashes content and falling number which decrease noodle-making quality of winter wheatSignificant correlations occurred between fresh-noodle and dry-noodle in all items including total score. Noodle-making quality significantly correlated with flour quality and dough Theological. Among all grain and flour quality, gluten content, stability time,ashes content, grain test weight, and hardness are important to noodle total score according to their correlation index with noodle quality.2. Studies on physiology and biochemistry basis:Study on protein mechanism indicated that nitrogen had an obvious effect on nitrate reductase (MR) activity in flag leaf. Soluble protein in flag leaf, which implies senescence of flag leaf, tented to decline with the increase of nitrogen fertilization. Nitrogen increased protein quality both in quantity and in quality by changing glutenin to gliadin ratio. Nitrogen fertilization had a significant effect on GMP content of the grains.It was also found that nitrogen fertilization has less influence on starch than on protein. Though there is a visible change in starch content, the ratio of amylopectin to amylase keep no obvious change. There was a difference between the two cultivars in the effects of nitrogen fertilization on activity of sucrose-phosphate synthsase (SPS) in flag leaves and on sucrose synthase (SS) in grains.3. Effect of nitrogen on production:Nitrogen fertilization added yield significantly. For YN15, the nitrogen application increased the ears per unit area and grains per ear, and enhanced the photosynthesis of flag leaves during filling. For JM19, the nitrogen application added the weight of grain significantly and prolonged the photosynthesis function period. So, nitrogen affected grain yield through different ways in two cultivars.4. Nitrogen's accumulation and distribution:Nitrogen concentration of the plant reached its summit at about 14 days after anthesis. As compared with other vegetative parts, stem is the most important pool for nitrogen accumulation. Most of nitrogen in vegetative parts was transferred to kernels during maturing. There is little nitrogen left in stem in YN15 at maturity while much remained in JM19. As the nitrogen fertilization increased, the contribution of nitrogen of flag leaves to kernel added while that of stems lessened.Based on the correlations of nitrogen fertilization with stability time, ashes content, gluten content, falling number, fresh-noodle total score, grain protein content, yield and grain test weight, the effects of nitrogen fertilization were evaluated. The result showed that the highest scores, 0.9496 and 0.9027, were gotten in high-level fertilization for YN15 and middle-level fertilization for JM19, respectively. |
