Abstract: In order to study the response mechanism of nitrogen fertilizer to the antioxidant properties of spring wheat under high temperature stress after anthesis and  clarify the physiological mechanism and operational mechanism of nitrogen to alleviate the harm of high temperature, in 2019, the split plot design was adopted with five nitrogen applications including 0 (N0), 75 (N1), 150 (N2), 225 (N3) and 300 (N4)kg·hm^-2 (primary zone) and two temperatures including (25±2)℃(CK) and (35±2)℃(HT) (secondary zone). Carotenoid content, superoxide dismutase (SOD) activity, peroxidase dismutase (POD) activity, catalase dismutase (CAT) activity, malondialdehyde (MDA) content, proline (Pro) content, superoxide anion radical (O^-₂·) content in flag leaf of spring wheat and their relationship with yield were analyzed. The results showed that the application of nitrogen fertilizer could significantly increase the contents of carotenoid, Pro and nitrogen in flag leaf, and improve the activities of SOD, POD, CAT and other enzymes, with the best effect of N3 treatment. Compared with CK, the content of carotenoids and the activities of SOD, POD and CAT in flag leaves  decreased after high temperature stress, and the degree of decrease was the smallest under N3. In addition, the contents of MDA and O^-₂· in flag leaf  increased significantly after high-temperature stress compared with CK, with the largest increase under the N0 treatment and the smallest increase under the N3 treatment. With the increase of nitrogen application, the 1 000-grain weight and yield of spring wheat showed a trend of increasing first and then decreasing. The yield of N3 treatment was the highest, 8.64 (CK) and 8.09 (HT) t·hm^-2, respectively. Compared with CK, the yields after high-temperature stress was decreased significantly, with a decrease from 7.81% to 33.71%. In conclusion, the carotenoid content and activities of  SOD, POD and CAT  in flag leaf under high-temperature stress  significantly decreased, and the MDA and O-2· contents  increased significantly, which led to an increase in the degree of membrane lipid peroxidation and premature aging. A suitable amount of nitrogen application (225 kg·hm^-2) could effectively resist high temperature stress and alleviate premature aging by maintaining  high activities (SOD, POD and CAT) and contents of Pro and carotenoid, and reducing the contents of MDA and O^-₂·, which could provide theoretical basis and technical support for high and stable yield of spring wheat.

Key words: spring wheat, nitrogen application, post-anthesis high temperature, antioxidant properties, yield

摘要： 为研究花后高温胁迫下氮肥对春小麦抗氧化特性的响应机制，阐明氮素缓解高温危害的生理机理及运筹机制，2019年采用裂区设计，主区为0 (N0)、75 (N1)、150 (N2)、225 (N3)和300 (N4) kg·hm^-2 5个施氮量处理，副区为(25±2)℃(CK)和(35±2)℃(HT)2个温度处理，研究不同温度处理下施氮量对春小麦旗叶中超氧化物歧化酶(superoxide dismutase, SOD)、过氧化物酶(peroxidase dismutase, POD)、过氧化氢酶(catalase dismutase, CAT)活性的影响及对类胡萝卜素、丙二醛(malondialdehyde, MDA)、脯氨酸(proline, Pro)、超氧阴离子自由基(superoxide anion radical, O^-₂·)含量和产量的影响。结果表明，与常温处理相比，高温胁迫后春小麦旗叶类胡萝卜素含量、SOD、POD和CAT活性均出现不同程度的下降，且丙二醛含量和超氧阴离子自由基含量明显增加，导致膜脂过氧化程度和早衰现象加剧，产量显著下降，降幅为7.81%～33.71%。而施加氮肥能显著增加春小麦旗叶中类胡萝卜素、Pro和氮的含量，提高SOD、POD和CAT酶活性;且随着施氮量的增加，春小麦的千粒重和产量呈先增后降的趋势，在N3处理时最高，分别为8.64(CK)和8.09×10³ kg·hm^-2(HT)，分别较N0处理增产67.12%和97.80%。由此表明，合理的施氮量可有效抵御高温胁迫，使小麦SOD、POD和CAT活性及脯氨酸和类胡萝卜素含量保持较高水平，并降低丙二醛和超氧阴离子自由基含量，从而缓解高温胁迫导致的早衰，最终提高小麦产量。因此，采用225 kg·hm^-2(N3)施氮量能有效降低花后高温引起的减产，为春小麦宁春50号高产、稳产、优质栽培模式提供理论依据和技术支撑。

关键词: 春小麦, 施氮量, 花后高温, 抗氧化特性, 产量