2022年6-9月以安科985为试验材料，在玉米灌浆期自然高温胁迫条件下(2022年夏高温持续时间长、范围广、强度大、极端性强)，灌施不同浓度褪黑素(MT)溶液，0(CK)、100(MT100)、200(MT200)、300(MT300) μmol/L，研究不同处理下玉米叶片光合特性、荧光特性、抗氧化酶活性与产量形成的影响。结果表明，褪黑素处理显著增加了玉米行粒数、穗粗、穗长、百粒重和单株产量，降低了秃尖长度，100、200、300 μmol/L浓度时产量分别较对照增加92.53%、134.8%、111.84%。褪黑素处理后叶片SPAD值、N含量、净光合速率、气孔导度和蒸腾速率显著增加，胞间二氧化碳浓度显著降低，100、200、300 μmol/L浓度时净光合速率分别较对照增加了45.15%、73.17%、56.30%。与对照相比，褪黑素处理下ΦPSⅡ、ETR、qN、qP和Fv/Fm均显著上升，100、200、300 μmol/L处理下ΦPSⅡ较对照分别增加21.86%、30.05%、12.30%，Y(NO)和F0显著下降。200 μmol/L处理显著提高叶片抗氧化酶活性(SOD、POD、CAT)，丙二醛MDA含量显著降低较对照降低47.88%。褪黑素处理后，干物质积累量和干物质向籽粒的分配比例显著增加。自然高温胁迫下，褪黑素处理可增强玉米抗性，其中200 μmol/L效果最佳。

From June to September 2022, Anke 985 was used as the experimental material. Under the condition of natural high temperature stress at the filling stage of maize ( long duration, wide range, high intensity and strong extremeness of high temperature in summer of 2022 ), different concentrations of melatonin ( MT ) solution 0 ( CK ), 100 ( MT100 ), 200 ( MT200 ), 300 ( MT300 ) μmol/L ) were set to study the Effects of different treatments on photosynthetic characteristics, fluorescence characteristics, antioxidant enzyme activities and yield formation of maize leaves. The results showed that Melatonin treatment significantly increased the number of kernels per row, ear diameter, ear length, 100-grain weight and yield per plant, and decreased the length of bald tip. The yield at 100,200 and 300 μmol / L concentrations increased by 92.53 %, 134.8 % and 111.84 %, respectively, compared with the control. The SPAD value, N content, net photosynthetic rate, stomatal conductance and transpiration rate of leaves increased significantly after melatonin treatment, and the intercellular carbon dioxide concentration decreased significantly. The net photosynthetic rate increased by 45.15 %, 73.17 % and 56.30 % at 100,200 and 300 μmol / L, respectively. Compared with the control, ΦPSII, ETR, qN, qP and Fv / Fm were significantly increased under melatonin treatment. Under 100,200 and 300 μmol / L treatments, ΦPSII increased by 21.86 %, 30.05 % and 12.30 %, respectively, compared with the control, and Y ( NO ) and F0 decreased significantly. The antioxidant enzyme activities ( SOD, POD, CAT ) of leaves were significantly increased by 200 μmol / L treatment, and the MDA content was significantly decreased by 47.88 % compared with the control. After melatonin treatment, dry matter accumulation and dry matter distribution to grains increased significantly. Under natural high temperature stress, melatonin treatment can enhance maize resistance, and 200 μmol / L is the best.

安徽高校自然科学研究重大项目(KJ2020ZD010)、安徽省财政农业科技成果转化应用项目(2021ZH015)