Mechanism Of Continuous Negative Pressure Water Supply On Maize Growth Regulation And Water Use Efficiency Improvement

The test studied the effect of continuous negative pressure water supply on the maize growth and development,yield and water use efficiency,it can provide a theoretical basis for the development of new water-saving irrigation technologies,as well as for fully tapping into the potential for water-saving and yield increase in maize cultivation;finally,it will have important scientific value for further exploring the relationship between crops and soil moisture.The experiment was carried out in the pot experiment base of Heilongjiang Bayi Agricultural University in 2019 and 2020,among them,four treatments of watering irrigation（CK）,-5k Pa,-10 k Pa,and-15 k Pa were set to screen the appropriate water supply pressure in 2019;in 2020,four treatments was set including continuous negative pressure water supply-5k Pa（SW）,continuous irrigation water supply control（CW）,negative pressure limited water supply（-10 k Pa）control（LW）,and simulated drip irrigation control（DW）were set up,SW uses a negative pressure irrigation system（NPI）to control the continuous negative pressure water supply,and the changes of growth and development,physiological characteristics,nutrient uptake,yield and water use efficiency of maize（variety:Xianyu 335）under continuous negative pressure water supply were studied by pot planting in a rain-proof shed;finally,metabolomic and transcriptomic techniques were used to analyze the physiological and molecular mechanisms of maize in response to continuous negative pressure water supply.The results show that:（1）The comparison results of different continuous negative pressure water supply pressure show that maize plant height and stem diameter of-5k Pa was higher than CK,-10 k Pa and-15k Pa,the dry matter accumulation of roots,stems,leaves,bracts,axes and grains,and nitrogen,phosphorus and potassium nutrients uptake of-5k Pa was significantly higher than CK,-10 k Pa and-15 k Pa,the final yield of-5k Pa was 38.73%,86.41%and 364.92%higher than CK,-10 k Pa and-15 k Pa respectively;the total water consumption of-5k Pa was 25.35%lower than CK,and the water use efficiency of biomass and economic yield of-5 k Pa was 75.50%and 85.96%higher than control,respectively;compared with CK,root activity and nitrate reductase activity of-5k Pa was significantly increased,the contents of malondialdehyde（MDA）,proline,soluble sugar and soluble protein,and the activities of superoxide dismutase（SOD）,peroxidase（POD）,catalase（CAT）and polyphenol oxidase（PPO）were decreased,and the photosynthetic rate was significantly increased.（2）Continuous negative pressure water supply made the soil water content stable between24.44%-25.87%,belonging to the weak time variation type;DW treatment of soil moisture content in a dry and wet alternating cycle state belongs to a moderate temporal variation type;the water consumption of SW was 70.30%and 58.26%reduced,and the water use efficiency was 2.49 times and 2.01 times higher than CW and DW respectively;the water use efficiency of SW was significantly higher than LW.（3）The plant height and stem diameter,and dry matter accumulation in stem,leaf and grain at maturity of continuous negative pressure water supply treatment was higher than DW,LW and CW,and the yield can be increased by 44.10%,70.91%,and 22.47%respectively;SW was significantly increased the economic coefficient but significantly reduced the accumulation of root dry matter compared with DW and CW.（4）The root vigor and nitrate reductase activity of continuous negative pressure water supply treatment was higher than DW,LW and CW,O₂^-and MDA content of SW in maize roots,leaves and stems was lower than DW,LW and CW;the activity of antioxidant enzymes（SOD,POD,CAT,APX）and polyphenol oxidase and the content of osmotic regulators（free proline,soluble protein,soluble sugar）of SW in maize roots,stems,and leaves was decreased;the net photosynthetic rate of SW was 31.83%,46.31%and 11.65%higher than DW,LW and CW,respectively.（5）The nitrogen uptake in leaves,cob and grain of continuous negative pressure water supply treatment was 24.32%,50.12%and 61.46%,phosphorus uptake was 33.61%,24.75%and58.06%,and potassium uptake was 15.81%,57.10%and 39.06%higher than DW at the maturity stage;nitrogen,phosphorus and potassium uptake in stem,leaf and grain of SW was significantly higher it in CW,its uptake in stem,leaf,bract,cob,grain of SW was significantly higher than it in LW,and its uptake in root of SW was significantly lower than DW and CW.（6）The results of metabolomics research indicate that there were 121 differential metabolites（46 down-regulated,75 up-regulated）in the SW and DW comparison group of maize leaves,50 differential metabolites（23 down-regulated,27 up-regulated）in SW and LW comparison group,120 differential metabolites（64 down-regulated,56 up-regulated）in SW and CW comparison group,211 differential metabolites（135 up-regulated,76 down-regulated）in SW and DW comparison groups of roots,and these differential metabolites were annotated into KEGG pathways such as amino acid metabolism,biosynthesis of other secondary metabolites,energy metabolism,and carbohydrate metabolism.（7）The results of transcriptome research show that there were 2505 differentially expressed genes in maize leaves（440 up-regulated,2065 down-regulated）in SW and DW comparison group,2951 in SW and LW comparison group（426 up-regulated,2525 down-regulated）,and1387 in SW and CW comparison group（242 up-regulated,1145 downgrades）;these differentially expressed genes are enriched in GO terms such as redox process,chloroplast,photosynthesis,oxidoreductase activity,mitochondria,transcription,and ATPase activity;continuous negative pressure water supply significantly enriched the differentially expressed genes in maize leaves in the photosynthesis and oxidative phosphorylation KEGG pathways,eight high-fold up-regulated genes such as psb A and psb D may be the key genes for the significantly improved photosynthesis in maize,nine high-fold up-regulated genes including atp E and atp B may be the key genes for enhanced energy metabolism in maize.（8）Compared with drip irrigation,continuous negative pressure irrigation made maize root differentially expressed genes highly enriched in channel activity,water transport and water channel activity GO term,these genes highly up-regulated expression enhanced the ability of maize roots to absorb and transport water,thirteen high-fold up-regulated genes such as ZM00001D003006 and ZM00001D014285 may be the key genes to improve maize water use efficiency.In summary,the continuous negative pressure water supply treatment can maintain relatively stable soil moisture content,improve maize water use efficiency and photosynthetic rate,promote maize growth and development,reduce water stress effects,regulate the upregulation of key genes related to photosynthesis,energy metabolism,and water uptake and transportation in maize,regulate the relative accumulation and changes of key metabolites in maize plants;finally,the goal of water-saving and increased production of maize was achieved.