Effects Of Different Mineraliaztion Salt Water On Photosynthetic Characteristics Of Phragmites Australis At Bosten Lake Northern Shore

In recent years,the influence of the change of Bosten Lake water level has changed in water salinity,which has effect both growth and distribution of Phragmites Australis.By measuring the parameters of photosynthesis and growth of reed under different concentrations of salt water,we found the maximum salt tolerance threshold of the reed and find out the suitable salt water irrigation concentration,which provides the theoretical basis for the selection of the planting crops in the area.In April 2015,the artificial transplanting growth was relatively consistent with the healthy reed,after a period of time,as the research object,the artificial irrigation of different concentrations of salt water?1.4 g/L?5 g/L?10 g/L?15 g/L?20 g/L?,the photosynthetic parameters,photosynthetic light response parameters,photosynthetic-CO₂ parameters,chlorophyll fluorescence parameters and soil parameters of the reed were measured by Li-6400 XT portable photosynthesis system,soil moisture probe type SMS2 and meter type HH2,and so on.The growth data of the plant height and ground diameter were analyzed and compared.The results showed that the increase of salinity had no significant effect on the photosynthetic active radiation?PAR?,the temperature and relative humidity of air?Ta,RH?,CO₂ concentration of air?Ca?and the temperature of the surface soil.But with the increase of the salt concentration,the relative volume of the surface soil decreased gradually,and the conductivity of the surface soil increased gradually.The photosynthetic rate?Pn?daily variation curve of each salinity gradient reed generally has two peaks,the Pn of 1.4 g/L?Y1?value was significantly higher than the other 4 salt gradient samples?P<0.05?.With the increase of salt concentration,reed Pn gradually reduce,Y4 picked up a little bit Pn values,when the salt concentration of 20 g/L reeds when the minimum value of Pn,which showed that the photosynthesis of the reed was affected by salt stress.Through the Pn of reed day value on PAR in definite integral computation,Y1 definite integral value was maximum,Y5 was minimum,Y4 also picked up a little bit.When the concentration of the brine was less than 5 g/L,the photosynthesis of the reed was greatly restricted by the stomatal limitation.When the salt concentration is greater than 5 g/L,the photosynthesis of the reed is influenced by stomatal and non stomatal factors,The change of chlorophyll fluorescence value was not significant.When the salinity leads to decreased Gs reed,thus reducing the Tr,which makes WUE high rise.But high salt concentration makes the reeds filtration cell death,makes the Tr and WUE both reduced.When the salt concentration is more than 10 g/L,photosynthetic active radiation in the same light,the salt will significantly reduce the net photosynthetic rate and light reed,maximum photosynthetic efficiency(P_max)was decreased with increase of salt concentration.At the same time,the main chlorophyll fluorescence value was significantly lower?P<0.05?,when increased to 15 g/L,and significantly increased?P<0.05?,indicating that the reed of the experiment was about 15 g/L.The increase of plant height and ground diameter showed that the increase of salt concentration decreased the growth rate.But when the salt concentration of 15 g/L,the two values have rebounded slightly.Conclusion: To sum up,on the north shore of Bosten Lake,the largest salt threshold of the local reed was 15 g/L?1.5%?.If irrigation is needed,the concentration of salt is less than 5g/L.