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【目的】小麦灌浆过程中旗叶光合、抗氧化代谢与氮素营养密切相关,本研究通过田间试验,以进一步揭示其关系。【方法】试验选用多穗中粒(MM)型品种藁城8901(GC8901)和大穗大粒(LL)型品种山农1391(SN1391),设12gN·m-2(LN)和24gN·m-2(HN)2个氮肥处理,在田间条件下研究了小麦灌浆期旗叶光合色素含量、氮素含量、光合特性和抗衰老酶活性对氮素水平的响应。【结果】小麦开花后旗叶氮素含量与叶绿素含量呈下降趋势,净光合速率(Pn)、实际光化学效率(ΦPSⅡ)、开放的光系统Ⅱ反应中心的量子效率(Fv′/Fm′)和光化学猝灭系数(qp)在花后14d左右开始下降,光系统Ⅱ的最大光化学效率直到衰老末期才有小幅下降,而非光化学猝灭系数(NPQ)呈上升趋势。旗叶光能的吸收和利用之间存在矛盾,这是促其衰老的重要原因。与MM型小麦品种GC8901相比,LL型品种SN1391群体较小,籽粒灌浆后期旗叶的光合色素含量高,光系统Ⅱ的活性下降慢,净光合速率高;同时,抗衰老酶活性下降慢,膜脂过氧化程度轻。氮素水平对2个品种籽粒灌浆过程中旗叶的光合及抗氧化代谢的影响不同。LL型品种SN1391表现为,增施氮肥后旗叶光系统Ⅱ的开放程度和实际光化学效率提高,热耗散降低,净光合速率提高;旗叶的SOD、POD、CAT和APX活性均提高,膜脂过氧化程度降低。增施氮肥后MM型品种GC8901光系统Ⅱ活性下降,用于热耗散的能量增加,光合速率降低;抗氧化酶系活性下降,膜脂过氧化程度加重。【结论】小麦生育后期旗叶光能吸收和利用间的矛盾是促其衰老的重要原因。不同类型小麦品种旗叶生育后期的光合及抗氧化代谢存在显著差异。施用氮肥对小麦旗叶光合、衰老特性的影响因品种类型而不同。
【Objective】 Flag leaf photosynthesis, antioxidant metabolism and nitrogen nutrition are closely related to grain filling in wheat. In this study, field trials were conducted to further reveal its relationship. 【Method】 In this experiment, we selected Tancheng 8901 (GC8901) and Shannong 1391 (SN1391) with large panicle type (MM) and 12gN · m-2 (LN) and 24gN · m- 2 (HN) were used to study the response of nitrogen content to photosynthetic pigment content, nitrogen content, photosynthetic characteristics and anti-aging enzyme activity of flag leaves at wheat grain filling stage under field conditions. 【Result】 The results showed that the nitrogen content and the chlorophyll content of flag leaf decreased after flowering. The net photosynthetic rate (Pn), actual photochemical efficiency (ΦPSⅡ), the quantum efficiency (Fv ’/ Fm’) of open photoreaction center Ⅱ The photochemical quenching coefficient (qp) began to decline about 14 days after anthesis, and the maximum photochemical efficiency of photosystem Ⅱ did not decrease slightly until the end of senescence, while the non-photochemical quenching coefficient (NPQ) showed an upward trend. There is a contradiction between the absorption and utilization of the flag leaf light energy, which is an important reason to promote its aging. Compared with the GC wheat cultivar GC8901, the SN1391 population of LL type cultivars was smaller, the content of photosynthetic pigments in the flag leaves at the late grain filling stage was higher, the photosystem Ⅱ activity decreased slowly, and the net photosynthetic rate was higher. At the same time, Lipid peroxidation degree of light. The effect of different nitrogen levels on the photosynthesis and antioxidant metabolism of flag leaves during grain filling of two cultivars was different. LL type SN1391 showed that the opening degree and the actual photochemical efficiency of flag leaf system Ⅱ increased, the heat dissipation decreased and the net photosynthetic rate increased after applying nitrogen fertilizer. The activity of SOD, POD, CAT and APX in flag leaf increased Reduced lipid peroxidation. After the application of nitrogen fertilizer, the activity of light system Ⅱ of MM type GC8901 decreased, the energy for heat dissipation increased, the photosynthetic rate decreased, the activity of antioxidant enzymes decreased, and the degree of membrane lipid peroxidation increased. 【Conclusion】 The contradiction between the absorption and utilization of light energy at the flag leaves of wheat during late growth stage is an important reason for its aging. There were significant differences in photosynthesis and antioxidant metabolism in different types of wheat flag leaf at later growth stage. The effect of applying nitrogen fertilizer on photosynthesis and senescence characteristics of wheat flag leaf varied with different types of cultivars.