施氮量对济麦20旗叶光合特性和蔗糖合成及籽粒产量的影响

在田间高产条件下，研究了施氮量对强筋小麦品种济麦20旗叶光合特性、蔗糖合成及籽粒产量的影响。结果表明，在0～168 kg hm^-2施氮量范围内，随施氮量的增加，旗叶蒸腾速率提高，气孔导度增大，细胞间隙二氧化碳浓度降低，旗叶净光合速率与蔗糖磷酸合酶活性显著提高，从而促进旗叶蔗糖合成，提高生物产量、籽粒产量和氮肥利用率；施氮量增加至240 kg hm^-2，旗叶净光合速率、蔗糖磷酸合酶活性、蔗糖含量和生物产量显著提高，但收获指数降低，籽粒产量和氮肥利用率无显著变化。施氮量继续增加至275 kg hm^-2，旗叶蒸腾速率、气孔导度、气孔限制值和净光合速率均显著降低，细胞间隙二氧化碳浓度则显著升高，旗叶光合作用受非气孔限制，蔗糖磷酸合酶活性、蔗糖含量、生物产量和收获指数均显著降低，籽粒产量减少，氮肥利用率降低。在本试验条件下，济麦20的适宜施氮量为168~240 kg hm^-2。

Effects of Nitrogen Fertilizer Rate on Photosynthetic Character, Sucrose Synthesis in Flag Leaves and Grain Yield of Strong Gluten Wheat Jimai 20

Nitrogen needed by the growth and development of wheat is essential for grain yield formation. The content of chlorophyll, net photosynthetic rate in leaves, photosynthate accumulation and yield are increased with nitrogen fertilizer application. However, yield and nitrogen fertilizer use efficiency are decreased by excessive nitrogen application. Thus appropriate nitrogen rate is essential for profitable yields and efficient nitrogen utilization. The objectives of this study were to determine the effects of nitrogen fertilizer rate on photosynthetic character, sucrose synthesis in flag leaves and grain yield of wheat, for providing the theory basis on appropriate amount of nitrogen supplication in production。 The field experiments were carried out on high fertile soil with organic matter 12.94 g kg^-1, total nitrogen 0.78 g kg^-1, alkalihydrolysable nitrogen 84 mg kg^-1, available phosphorus 11.84 mg kg^-1 and available potassium 83 mg kg^-1 in Zhongcun Village, Longkou City, China, using the cultivar “Jimai 20” which has high yield and strong gluten potential. Five nitrogen treatments (N0, N1, N2, N3, N4, N5) were set, with 0, 96, 168, 240, and 276 kg N·ha^-1 respectively, using urea as the nitrogen fertilizer. Half of the nitrogen fertilizer was applied before sowing, the other half topdressed at jointing stage. The treatments were supplied with 105 kg P₂O₅ ha^-1 and 135 kg K₂O ha^-1 before sowing. Each treatment had three replicates, and the plot area was 3 m × 8 m = 24 m². The basic seedlings were 150 plant m^-2. The results showed that intercellular CO₂ concentration decreased, transpiration rate, stomatal conductance, net photosynthetic rate, sucrose-phosphate synthase activity in flag leaves, sucrose synthesis, biological yield, grain yield and nitrogen fertilizer use efficiency increased with nitrogen applied form 96 to 168 kg ha^-1. Net photosynthetic rate, sucrose-phosphate synthase activity, sucrose content in flag leaves and biological yield increased significantly, but harvest index decreased, grain yield and nitrogen fertilizer use efficiency were not affected significantly by applying nitrogen of 240 kg ha^-1. Transpiration rate, stomatal conductance, stomatal limitation value and net photosynthetic rate in fag leaves decreased significantly, but intercellular CO₂ concentration increased, sucrose-phosphate synthase activity, sucrose content in flag leaves, biological yield, harvest index, grain yield and nitrogen fertilizer use efficiency decreased by excessive nitrogen applied with 275 kg ha^-1. The decrease of net photosynthetic rate mainly resulted from mesophyll factor. The appropriate amount of nitrogen application under the condition of this experiment with strong gluten cultivar “Jimai 20” is 168–240 kg ha^-1。