Effects Of Waterlogging Stress On Agronomic Characteristics,Physiological Characteristics And Yield Of Maize

Maize?Zea Mays L.?is an important food crop,feed crop and cash crop in China and plays an important role in China's agricultural production.Waterlogging is one of the major agrometeorological disasters facing many countries in the world.The experiment was conducted at the Xiangyang Experimental Base of Northeast Agricultural University from 2017 to 2018.Through the field waterlogging simulation screening experiment,21 high-quality and high-efficiency maize varieties in Heilongjiang Province were treated with waterlogging for 3,5,7,9 days and subsurface waterlogging for 4,6,8 and 10 days at the three-leaf stage.Cluster analysis was conducted with plant height,SPAD value,underground and ground dry weight as screening indicators.The representative maize varieties DMY1 and KY16 were selected as experimenta l materials.In the V3,V6 and VT stage,water was waterlogged for 3,6 and 9 days and subsurface waterlogged for 5,10 and 15 days,respectively,with no flooding as a control,to explore the effects of waterlogging and subsurface waterlogging stress on agronomic characteristics,antioxidant system,photosynthetic system,nitrogen metabolism,grain filling characteristics and yield of maize,aiming to clarify the physiological ways of waterlogging treatment affecting the growth and yield of maize.The main results are as follows:1.Through screening experiment,among 21 maize varieties,14.29%,57.14% and 28.57% were waterlogging-tolerant,intermediate and sensitive,respectively.The correlation analysis showed that the interaction of waterlogging duration and varieties had significant effects on plant height and SPAD value of maize seedlings.Waterlogging duration treatment had a significant effect on root dry weight.2.The plant height,ear height,stem length,stem diameter,rind penetration strength and transverse bending strength of the two maize varieties showed a decreasing trend with the prolongation of waterlogging and subsurface waterlogging stress,the most significant effect was on 9 days of waterlogging and 15 days of subsurface waterlogging at V3 stage.Response to the control treatment,the plant height of DMY1 and KY16 decreased by 17.77% and 16.43%,15.14% and 15.82%,the rind penetration strength of DMY1 and KY16 reduced by 38.36% and 38.96%,40.38% and 42.36%,respectively.After waterlogging stress,the dry matter accumulation and distribution of maize stems and leaves increased,and the dry matter accumulation and distribution of maize grains decreased.In addition,the thickness of stem cortex and the number of vascular bundles decreased after waterlogging stress,which increased the risk of stem lodging.Waterlogging stress treatment at V3 stage had the most significant effect on the agronomic characteristics of stem,followed by V6 stage,and the smallest effect at VT stage.3.After waterlogging and subsurface waterlogging stress,maize leaves produced excessive O₂^-,H₂O₂ and MDA,and the SPAD value decreased,which affected the photosynthetic activity and photosynthesis of maize leaves.The activities of PEPcase and RUBPcase,P_n,G_s,T_r and C_i of maize leaves were significantly increased.The activity of SOD,POD and CAT reached the highest level at 9 days of waterlogging and 15 days of subsurface waterlogging,indicating that the plants could produce a large amount of antioxidant enzymes to remove excessive ROS in a short time under waterlogging stress.When the waterlogging duration is too long,the activity of antioxidant enzymes in plants is insufficient to resist the stress conditions,which damages the protective enzymes system,aggravates the degree of membrane lipid peroxidation,and leads to the increase of MDA content in leaves.At the same time,the content of proline and soluble protein in leaves increased with the increase of waterlogging duration,which could effectively maintain cell osmotic potential and cell structure and function.Waterlogging stress at V3 stage had the greatest effect on leaves,followed by V6 stage and less effect on VT stage.4.Waterlogging treatment significantly reduced the nitrogen accumulation and distribution of two maize cultivars.9 days of waterlogging and 15 days of subsurface waterlogging at V3 stage had the greatest impact on the nitrogen accumulation and distribution.Nitrogen accumulation and distribution in stems and leaves of maize increased after waterlogging stress,while that in grain was lower than that in control treatment.Nitrate reductase?NR?and glutamine synthetase?GS?activities in two maize leaves decreased after waterlogging stress at different grow th stages.Waterlogging treatment at V3 stage had the most significant effect on them.NR and GS activities of DMY1 at 9 days of waterlogging at V3 stage decreased by 38.21% and 40.90% compared with those of control treatment.KY16 decreased by 47.32% and 46.11% respectively,followed by V6 and VT stage.5.After waterlogging treatment,Wmax,Gmax,Gave and P of the grains of the two maize varieties decreased significantly,which hindered the grain filling process,made the "sink" of maize grains lack sufficient "source" material supply,reduced ear length and ear diameter of maize,increased bald tip length,and also reduced the number of ears and 100-grain weight of maize,resulting in the reduction of the grain yield of DMY1 and KY16,and the most significant effect on the waterlogging for 9 days and subsurface waterlogging for 15 days at V3 stage.In 2018,the grain yields of DMY1 and KY16 were reduced by 60.67% and 61.15%,70.21% and 71.65%,respectively,compared with CK treatment.The waterlogging and subsurface waterlogging at the V3 stage had the greatest impact on the ear traits and yield,followed by V6 stage and VT stage.