| Huang-Huai-Hai area,as an important main corn producing area,is short of water resources,uneven distribution of time and space,and mismatch between precipitation and crop water requirement.These factors make summer corn often subject to drought stress during the growth and development process,which makes it difficult to increase the yield per unit area of corn.In order to explore the effects of different degrees of drought stress on photosynthesis,antioxidant system and yield of summer maize,water control was carried out in pool planting from 2020 to 2021.Irrigation before and after flowering was estimated according to the growth water requirement of summer maize for many years.Water control was started when the 14 th leaf was fully developed,and irrigation was conducted every 7 days,divided into three times.Set four water gradients: 100% Eapotranspiration ETC(CK),70% ETC(WD1),40% ETC(WD2),and 0 ETC(WD3).The preliminary experiment found that L-arginine could significantly improve the drought resistance of maize at seedling stage.In order to explore the regulation effect of different application methods,five treatments were set up through pot experiment: Normal water treatment(CK),drought treatment(WD,50% ± 5% of field capacity),drought + L-Arginine seed mixing treatment(DM),drought + L-Arginine foliar spraying treatment(DF),drought + L-Arginine seed mixing + foliar spraying treatment(DM + DF).In order to study the effect of optimal application of L-Arginine on field yield,this experiment conducted a water control experiment in pool planting in 2022.When 14 leaves were fully developed and dry at the stage of tasseling,four treatments were set: normal water treatment(CK),application of L-Arginine(MS + FA),drought treatment(WD,50% ± 5% of field water capacity),drought and L-Arginine(DM + DF)were applied to determine leaf photosynthesis,antioxidant system and yield.The specific results are as follows:(1)The photosynthetic performance of summer maize was significantly affected by drought stress.The results showed that drought stress had a significant effect on the photosynthetic performance of summer maize.The chlorophyll content,photosynthetic performance index(PIABS),leaf area index and photosynthetic potential of the leaves were lower than those of the control group,and the accumulation of photosynthetic assimilates was also hindered to some extent.In addition,the study also found that the antioxidant enzyme activity of maize leaves increased after drought stress,and the deeper the drought degree,the greater the increase of antioxidant enzyme activity.Compared with CK,WD1,WD2 and WD3 reduced the kernel number per ear in 2020-2021 by 3.10%,21.06%,25.28% and 12.11%,27.35%,40.75%,respectively.Compared with CK,the hundred seeds weight of WD1,WD2 and WD3 decreased by 8.99%,9.66%,16.15% and 18.86%,23.42%,30.65%,respectively.Compared with CK,the yield of WD1,WD2 and WD3 decreased significantly by 34.34%,51.83%,53.56% and 19.32%,45.79% 54.61%,respectively.(2)Different application modes of L-Arginine could increase the relative chlorophyll content(SPAD)and photosynthetic performance index(PIABS)of maize leaves under drought conditions,and also significantly increase the leaf area index,specific leaf weight and growth rate of maize plants.Among them,the effect of seed dressing + foliar spraying composite measures to alleviate drought is more significant.The data show that: The absolute growth rates of DM,DF and DM + DF were increased by 59.65%,39.19% and 106.09% compared with WD,respectively,respectively.Compared with WD,the leaf mass per area increased significantly by 91.40%,86.67% and 116.71%,respectively.The leaf area index during 15 days of drought increased significantly by 486.87%,453.84% and 943.45%,respectively.Among them,the effect of the combined measures of seed mixing and spraying was more significant.(3)The activities of superoxide dismutase,peroxidase and catalase in maize leaves under drought stress were significantly increased by using 350 μmol L-1 L-Arginine in seed dressing and foliar spraying,the content of malondialdehyde and the production rate of active oxygen species were decreased,and the contents of soluble sugar and soluble protein were increased,which enhanced the stress resistance of the plant.In addition,the application of L-Arginine can also increase the chlorophyll content of leaves,improve the photosynthetic capacity of leaves,and delay leaf senescence.In addition,the application of L-Arginine can also increase the ear length,row number and ear number of corn,reduce the bald tip length and abortion rate,and improve the yield of corn.The treatment with L-Arginine reduced the length of bald tip and the rate of abortion by 22.59% and 40.86%,while the number of grains per ear and yield increased by 41.53% and 13.89%,respectively.In conclusion,different degrees of drought treatment inhibited the photosynthesis of maize leaves,increased the degree of lipid peroxidation of cell membrane,and caused metabolic disorders in cells.Under the drought treatment,the number of grains per ear and the weight of grains decreased,and thus the grain yield decreased.However,L-Arginine treatment could increase the photosynthetic capacity of maize plants under drought conditions,improve the water metabolic balance of maize plants,enhance the antioxidant system,maintain the stability of cell membrane,and thus enhance the drought resistance of maize plants and increase the yield. |
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