| Xinjiang is the main cotton producing area in China,where belongs to arid and semi-arid areas.The insufficient precipitation has seriously affected the yield and quality of cotton.Flowering and boll stage is the key period of cotton yield formation,and also the period of cotton water consumption is the largest and most sensitive to water.Exogenous substances can improve the drought resistance of cotton and alleviate the effect of drought on cotton yield and quality.Based on the exogenous substances screened in 2017,field experiments were conducted again in 2018.Xinluzao 42 cotton cultivar was used as test material,split plot design was adopted,and three water treatments were used in the main plot.Three water treatments were set up in cotton flowering and boll stage:W1:normal irrigation（4200 m3/hm2）,irrigation quantity and times according to the requirements of normal field production,W2:75%（3525 m3/hm2）of total irrigation amount in flowering and boll stage and W3:50%（2850 m3/hm2）of total irrigation amount in flowering and boll stage.The accessory areas were foliar spraying with exogenous substances,T1:salicylic acid(0.1 mmol.L-1),T2:betaine(20 mmol.L-1),T3:brassinolide(1 mmol.L-1),CK as control.The effects of exogenous substances on cotton agronomic traits,dry matter accumulation,yield,fiber quality,antioxidant enzymes and osmotic adjustment substances under water stress at flowering and boll stage were analyzed by measuring cotton agronomic traits,dry matter accumulation and yield under different treatments.The physiological characteristics of cotton under water stress at flowering and boll stage were revealed to improve drought resistance,water saving and high yield of cotton.Cultivation provides theoretical basis.The main results are as follows:1.Effects of exogenous substances on agronomic characters,yield and quality of cotton under water stress at flowering and bolling stageWith the increase of water stress,cotton plant height,stem diameter,yield of Fu peach and autumn peach,seed cotton and lint cotton decreased,while the appropriate concentration of salicylic acid,Brassinolide and betaine could increase cotton plant height,stem diameter,Fu peach and autumn peach,seed cotton and lint yield in varying degrees.The seed cotton yields of W1,W2 and W3 were 3715.06 kg/hm2,3363.15 kg/hm2 and 2824.15 kg/hm2,respectively.The seed cotton yields of salicylic acid treatment were the highest and significantly different under the three water treatments（P<0.05）.It was also found that the regularity and elongation at break decreased first and then increased with the increase of water stress.However,under CK condition,there was no significant difference in cotton fiber quality among different water treatments.2.Effects of exogenous substances on dry matter accumulation in cotton under water stress at flowering and bolling stageWith the increase of water stress degree,the dry matter accumulation and growth characteristic value of cotton during rapid accumulation period decreased.The effects of exogenous substances on shoot dry matter were different under three water treatments.Under the conditions of W1,W2 and W3,the manifestations of exogenous substances were:T1>T3>T2>CK1,T1>T2>T3>CK2 and T1>CK3>T3>T2.Under different water stress,leaf area index and SPAD values were the same.UnderW1,W2andW3 conditions,the exogenous substances were T1>T2>T3>CK1,T1>T2>T3>CK2>T2>T3>CK3.3.Effects of exogenous substances on antioxidant enzymes and osmotic regulators in cotton under water stress during flowering and boll stageWith the extension of water stress time,SOD,POD activity and Pro content increased first and then decreased,while SS,SP and MDA content continued to increase.Spraying salicylic acid,Brassinolide and betaine increased SOD and POD activity,SS,SP and Pro content,and decreased MDA content.Spraying appropriate concentration of salicylic acid,betaine and Brassinolide on Cotton Leaves under water stress can increase the activity of antioxidant enzymes,alleviate the oxidative stress caused by drought,promote the accumulation of free proline and soluble sugar in cotton leaves,improve the osmotic adjustment ability of cotton leaves under water stress,improve the water relationship of leaves,maintain leaf swelling pressure,and alleviate the stress.Adverse effects of water stress on cotton at flowering and boll stage.Three exogenous substances and clear water were classified into three types:clear water was non-drought-resistant;Brassinolide and betaine were moderate drought-resistant;salicylic acid was strong drought-resistant;salicylic acid could effectively reduce the harm of water stress on cotton at flowering and boll stage. |
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