| The experiment adopted potted water control method,select no-drought tolerant soybean variety Suinong 26 and drought tolerant soybean variety Heinong 54,four treatments were set for the experiment: CK(maintaining 70% of the field water capacity in the whole growth period),T1(maintaining 60% of the field water capacity in 15 days of mild water stress in V1),T2(maintaining 50% of the field water capacity in 15 days of moderate water stress in V1),T3(maintaining 40% of the field water capacity in 15 days of severe water stress in V1),The physiological growth,endogenous changes and yield of soybean were studied in order to understand the response mechanism of Soybean under drought conditions and the compensation mechanism after rehydration,so as to provide a theoretical basis for water-saving and high yield cultivation of soybean in calcareous chernozem in Heilongjiang Province.The results show that:(1)The plant height,stem diameter and dry matter accumulation of Soybean under different degrees of water stress in V1 stage were reduced.Compared with the control treatment,the plant height of Suinong 26 under mild,moderate and severe water stress treatment decreased by 10.55%,20.5% and 21.73% respectively,and the stem diameter decreased by9.51%,25.11% and 24.96% respectively.Under mild water stress treatment,the stem dry matter accumulation was significantly higher than that of CK treatment,increased by 14.47%,Moderate and severe water stress reduced the dry matter accumulation of the variety,which decreased by 40.3% and 43.78% respectively compared with normal water supply treatment;The T1,T2 and T3 treatments of Heinong 54 decreased by 9.47%,11.05% and 18.95%respectively compared with CK treatment,and the CK treatment of Heinong 54 increased by3.14%,23.84% and 39.56% respectively compared with T1,T2 and T3 treatment.Water stress in V1 stage had a significant effect on the dry matter accumulation of Heinong 54.With the aggravation of stress,the dry matter accumulation of stem and leaf decreased significantly,and the light,moderate and severe water stress treatments were compared with CK treatment,the stem dry matter accumulation decreased by 10.04%,55.9% and 68.56%,and the leaf dry matter accumulation decreased by 7.03%,47.27% and 64.84%.After rehydration,all indexes recovered rapidly.(2)V1 water stress treatment could increase the activity of protective enzymes and the content of Osmoregulation Substances in soybean leaves,slow down the process of cell membrane lipid peroxidation in soybean,and lead to the accumulation of a large number of reactive oxygen species.Compared with CK treatment,the POD activity of Suinong 26 T1,T2 and T3 treatment increased by 30.42%,48.11% and 53.82% respectively,among which the difference between T2,T3 treatment and CK treatment reached a significant level;The change trend of POD activity in the leaves of Heinong 54 was consistent with that of Suinong 26,and there were significant differences between each treatment and the control treatment.Under mild and severe water stress,the increase of proline content in Suinong 26 was greater than that in Heinong 54.On the contrary,under moderate water stress,the proline content in leaves decreased as the growth period prolonged.In V1 stage,the content of MDA also increased with the deepening of water stress,and the increase range of Heinong 54 was higher than that of Suinong 26.Compared with the control treatment,the content of MDA under mild,moderate and severe water stress increased by 51.69%,55.76% and 57.23% respectively;Under mild,moderate and severe water stress,the content of MDA increased by 51.41%,77.01% and80.13% respectively.After rehydration,the antioxidant enzyme activity of leaves increased,the total antioxidant capacity increased,and the content of malondialdehyde decreased,but it was still higher than that of the control treatment.The MDA content of soybean Suinong 26 decreased the most under T2 treatment,while Heinong 54 decreased the most significantly under T3 treatment.(3)Water stress treatment at V1 stage would hinder chlorophyll synthesis and reduce the photosynthetic capacity of soybean.In the pod stage,the gas exchange parameters of Suinong26 reached the maximum under T1 treatment.PN,GS,CI and tr increased by 8.56%,28.07%,6.03% and 14.29% respectively compared with CK(P < 0.05);The gas exchange parameters of Heinong 54 increased first and then decreased.PN and GS reached the maximum under T2 treatment,while Ci and tr reached the maximum under T1 condition.(4)Water stress in V1 stage will affect the absorption and transport of nitrogen in various organs of soybean,the mild water stress will increase the nitrogen content in various organs of soybean Suinong 26.Compared with the control treatment,the nitrogen content in stem and leaf increased by 44.73% and 50%,which were significantly different from the control;Different degrees of water stress had different effects on the nitrogen content of various organs of Heinong 54.Moderate stress was conducive to the accumulation of nitrogen in the stem,which was 36.67% higher than CK,and the difference reached a significant level.Mild stress could increase the nitrogen content in the leaves,which was 9.41% higher than the control.Mild water stress and rehydration treatment were beneficial to the nitrogen accumulation of drought tolerant variety Suinong 26,while moderate water stress and rehydration treatment were beneficial to the nitrogen accumulation of drought tolerant variety Heinong 54.(5)Moderate water stress and rehydration were beneficial to the increase of soybean yield.The yield of Suinong 26 reached the maximum under mild water stress and rehydration,which increased by 30.1%,32.2% and 44.2% respectively compared with normal water supply,moderate and severe water stress and rehydration treatment;The yield of Heinong 54 reached the maximum under moderate water stress and rehydration,which was 7.8%,18.5% and 33.6%higher than that of normal water supply,moderate and severe water stress and rehydration respectively. |
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