限水灌溉下追氮水平对冬小麦旗叶光合特性及物质运转的影响

为给华北地区冬小麦节水栽培条件下氮肥合理运筹提供理论依据,以高产小麦品种周麦18为供试材料,在大田限水灌溉条件下,设置六个不同氮肥处理［各处理底施和追施氮量（底氮+追氮）分别为：0+0、120+0、120+60、120+120、120+180、120+240 kg·hm^-2］,研究了限水灌溉条件下追氮水平对冬小麦旗叶光合特性及物质运转的影响。结果表明,施氮量120+60 kg·hm^-2时,小麦产量最高,达到8 749 kg·hm^-2。限水灌溉条件下追氮水平对冬小麦旗叶光合特性及物质运转有较明显的调控效应,总体表现为,在0～120 kg·hm^-2范围内,随着追氮量的增加,旗叶净光合速率、气孔导度和叶绿素含量增大,胞间CO₂浓度降低,延缓了旗叶的衰老进程,延长了光合功能期,有利于光合产物的积累,而过高的追氮量（180～240 kg·hm^-2）并没有在更大程度上提高旗叶净光合速率和叶绿素含量以及降低胞间CO₂浓度;适当追氮（60 kg·hm^-2）虽然增加了花前贮藏物质和氮素的运转量,但运转率下降;过多的追施氮肥（120～240 kg·hm^-2）会导致花前贮藏物质和氮素运转量、运转率及对籽粒的贡献率显著降低。在本试验条件下,最适的施氮处理为120+60 kg·hm^-2。

Effect of Topdressing Amount of Nitrogen on Photosynthetic Characteristics and Assimilates Transportation in Winter Wheat under Limited Irrigation

In order to identify the effects of topdressing amount of nitrogen on photosynthetic characteristics of flag leaf and assimilates transportation in different organs under limited irrigation, the field experiment was carried out in Xunxian institute of agricultural sciences, Henan, China, using the cultivar "Zhoumai 18" which had high yield. Six nitrogen treatments (N0, N1, N2, N3, N4, N5) were set, and the amount of basal and topdressing nitrogen were 0+0, 120+0, 120+60, 120+120, 120+180 and 120+240 kg N·hm^-2, respectively. Net photosynthesis rate (Pn), stomatal conductance (Gn), intercellular CO₂ concentration (Ci) and chlorophyll content of flag leaves were measured using Li 6400 portable photosynthesis system with an open flow gas exchange system. The results showed that photosynthetic characteristics of flag leaf and assimilates transportation in different organs were regulated significantly under the top dress nitrogen application. The highest yield was 8 749 kg·hm^-2 in the 120+60 kg·hm^-2treatment. With topdressing amount of nitrogen from 0 to 120 kg·hm^-2, the flag leaf net photosynthetic rate and chlorophyll content increased,flag leaf senescence was delayed, period of flag leaf photosynthetic function was extended, and accumulation of photosynthetic products increased. But flag leaf net photosynthetic rate and chlorophyll content were not further increased by excessive topdressing amount of nitrogen from 180 to 240 kg·hm^-2. The translocation amount of pre anthesis dry matter and nitrogen were significantly increased by nitrogen applied with 120+60 kg·hm^-2, and the translocation efficiency of pre anthesis dry matter and nitrogen were high by lower nitrogen applied with 120+0 kg·hm^-2, the contribution of pre anthesis dry matter to grain was the highest by nitrogen applied with 120+60 kg·hm^-2, but the contribution of pre anthesis nitrogen to grain was the highest by nitrogen applied with 120+0 kg·hm^-2. The translocation amount, translocation efficiency and contribution of pre anthesis dry matter and nitrogen to grains were significantly lower with excessive topdressing amount of nitrogen from 120 to 240 kg·hm^-2. Without topdressing nitrogen applied, basal application of nitrogen significantly increased Pn and chlorophyll content of flag leaves, and promoted the translocation of pre anthesis dry matter and nitrogen.