| China is one of the largest saline countries(approximately 3.6 × 107 hm2)in the world,the area of cotton located in the saline is approximately 1.7 × 107 hm2,it has become an important development direction of China's agriculture that how to rationaly develop and utilize resources of saline land.Cotton has a strong tolerance of salt,it is a pioneer in the cultivation of crops in saline.cultivation of crops in saline has become the main direction.Movement of soil water and salt affected root growth environment,and by osmotic stress,ion toxicity,nutritional imbalance,causing cotton physiological and biochemical metabolic imbalance,affectting the growth,yield and quality of cotton formed.In this study,accord-ing to groundwater depth as the media,and they are provided the actual water and simula-tive salt stress test,through different salt water processings,as the core of the variations of soil moisture,salt concentration areas of water and salt space-time distribution in the whole growth period of cotton root system formed.Proven relations between of "leaf-bell" the material energy conversion throughout the reproductive cycle of cotton.Eventually it clear that the best water depth of coastal land reclamation area to drop water and salt of soil.1.Effects of Saline Water Table on the Soil Water and Salt Characteristics of Coastal Saline and Cotton YieldUnder different water depths of the spatial and temporal variations of soil water and salt,the cotton's output and quality was different.The results showed that:different groundwater depth can be formed in similar soil water and salt transport regularity,and as the water depth increases,the soil water content was gradually decreased in relative tenden-cy,the conductivity was also gradually reduce in same trend,showing a significant "syn-chronization." Soil magnetism of soil water and salt in time and space distribution has close relation with meteorological conditions.In time,a period of less rainfall,soil moisture con-tent increased conductivity decrease(2013);in a period more rainfall,relative soil water content has increased but the conductivity has decreased(2014).In space,when the high temperature and drought,relative water content of the upper is less than the lower relative water content,soil conductivity for upper is greater than the lower(2013 cotton season);and when more rain,it shows that the relative soil water content of upper is less than the lower,conductivity for upper is less than the lower(2014).2.Effects of Characteristics of Soil Water and Salt on the Leaf of bell Source-sink Activity of Cot-ton in Coastal Saline SoilThe effect under different water depth of 0.4 m and 2.4 m in the water and salt stress is most obvious.Because of the influence of cotton para leaf water and salt stress,chlorophyll a and b content in para leaf declined obviously,the value of Gs reduced,the cintent of Ci inclined.PS ? quantum yield decline,photochemical quenching(qP)decreased,non-photochemical quenching coefficient(qN)increased,which led to the boll leaf net photo-synthetic rate;SOD,POD,CAT activity increased,MDA content decreased;on leaf soluble sugar and amino acid content decreased,carbon and nitrogen ratio decreased,carbon and nitrogen metabolism is affected.Para bell synthetic fiber material critical sucrose content,cellulose content decreased callose content increased,yield and quality decreased.High rate of boll shell that "leaf of cotton boll to boll shell to cottonseed fibers" carbon circulation is blocked.Produce different water depth under water and salt stress on the environmental impact of the cotton boll leaf and normal physiological processes,resulting in a net de-crease Photosynthetic rate,reduced ability to produce substances.A decrease in substance to the blade boll transport,boll substance conversion process is affected,a large number of substances stay in the bell housing,the fiber rate.Further Dafeng optimum water depth in the area at the best 1.6m——-2.0m,1.8m-2.2m in the Nanjing.3.Effects of Characteristics of Soil Water and Salt on the Photosynthetic Characteristics,Yield and Fiber Quality of Cotton in Coastal Saline SoilAt the different stages of spatial and temporal distribution of water and salt,the test point that water depth at the highest sugar content is in 1.6m to 2.2m in Dafeng,at the highest content in Nanjing is 1.8m to 2.2m.Starch content is also highest in 1.6 m in dafeng,at 2.2 m in Nanjing.Dafeng sites in the water depth of 1.6 m,the sucrose of leef has the highest conversion rate,it is significantly higher than other processing.Nanjing is at 2.2 m The key enzyme of sucrose metabolism,Rubisco initial activity and cytoplasmic fructose 1,6-2 phosphatase activity came to maximum activity at 20 days after flowering.Dafeng sites is in water depth of 1.6-2.0 m.Enzyme activity was significantly higher than other processing.Sucrose synthase and sucrose phosphate synthase changes in peak shape under different water depth.Similarly dafeng in water depth of 1.6 m-2.0 m value is significant-ly higher than other treatment groups.Caused under different time and space distribution of water and salt water salt stress environment affect the normal process of the cotton para leaf sucrose metabolism,with the increase of water level of salt stress,the synthesis of sucrose content decrease,sending also fell to the bolls.Sucrose metabolism and transport of key enzyme activities are affected,and it eventually led to a decline in cotton yield and quality.Dafeng sites in water depth of 1.6-2.0 m at best,Nanjing is in the water depth of 1.8-1.8 m.In conclusion,Under different water depths,the environment of water salt stress af-fecedt the cotton para leaf and bell normal physiological metabolism process,resulting in a decline in leaf net photosynthetic rate,reduce ability of material produce.From the blade to the cotton boll,reducing conveying material.The change process of material in cotton boll is affected,a lot of material stay in the bell shells,fiber rate decline.The best water depth are obtained at 1.6 2.0 m best in Dafeng region.Nanjing is at 1.8 2.2 m. |
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