Effects Of Saline-alkali Stress On The Individual And Leaf And Clonal Growth Traits Of Phragmites Australias

With the excessive of human inappropriate economic activities and the change of natural climate,grassland which is one of the important types of terrestrial ecosystems is been constantly disturbed and destroyed.At present,the problems of grassland degradation,desertification and salinization are very serious.Salinization has become an important limiting factor in the productivity of Songnen grassland in China.Phragmites australis,as a dominant species in Songnen grassland,has many advantages,such as wide adaptability,strong resistance and high biomass.It plays an important role in improving soil environment.Therefore,it is of great theoretical and practical significance to study the mechanism of individual growth and asexual reproduction of Phragmites australis to different degrees of salinization.This study through the pot experiment and the simulation of salinity-alkalinity stress environment,set different salinity-alkalinity stress concentration gradient,salt stress treatment using neutral salt Na Cl,mixture respectively 0 mmol L-1,200 mmol L-1,400 mmol L-1solution,alkali stress treatment using alkaline salt Na2CO3,mixture respectively 0 mmol L-1,25 mmol L-1,50 mmol L-1 solution,repeat 3 times each processing.The growth condition,leaf characters and the characteristics of the clones are studied under the treatment of saline-alkali stress.The results are as follows:(1)With the increase of salt concentration,Phragmites australis total biomass,plant height,stem length,root length increased with salt stress concentration decreased significantly(P < 0.05),the stem and leaf biomass decreased under salt stress,decreased significantly under alkali stress(P < 0.05).The effect of alkali stress was significantly greater than that of salt stress(P < 0.05).(2)With the increase of the concentration of salt stress,Phragmites australis leaf length,leaf area,specific leaf area and leaf dry matter content was decreased,but the difference was not significant(p>0.05);the content of N and N/P increased significantly(P < 0.05),C/N decreased significantly(P < 0.05),C content and P content and C/P had no significant change.(3)The stalemate conductance and inter-cellular CO2 concentration of Phragmites australis leaf decreased significantly(P < 0.05),and transpiration rate first increased and then decreased.Water use efficiency,under salt stress,increased significantly(P < 0.05),and increased first and then decreased under alkali stress.The net photosynthetic rate of reed had no significant difference under salt stress,and decreased significantly under alkali stress(P < 0.05).(4)With the increase of the concentration of salt stress,strain,Phragmites australis tiller sub sub strains and the total number of sub roots under alkali stress decreased significantly(P < 0.05),under salt stress decreased;total buds decreased under saline alkali stress.The contents of Na+ in Phragmites australis increased significantly(P < 0.05),and the contents of K+ and NO3-decreased significantly,while Na+/K+ ratio increased significantly(P < 0.05).Cl-increased significantly under salt stress(P < 0.05),but there was no significant change under alkaline stress.The content of H2PO4-decreased significantly under alkali stress(P < 0.05),and there was no significant change under salt stress.