Effects Of Saline-alkali Stress On The Individual And Clonal Growth Traits Of Leymus Chinensis

With the excessive use of human inappropriate economic activities and the change of natural climate,Grassland which one of the important types of terrestrial ecosystems was constantly disturbed and destroyed.At present,the problems of grassland degradation,desertification and salinization were very serious.Salinization has become an important limiting factor in the productivity of Songnen grassland in China.Leymus chinensis as the dominant species of Songnen grassland,had high nutritional value,good palatability and other fine features.Therefore,it is of great theoretical and practical significance to study the mechanism of individual growth and asexual reproduction of L.chinensis to different degrees of salinization.Our study were designed two concentration gradients(salt stress concentration were 0,100,200 mmol·L-1 and alkali stress concentration were 0,25,50 mmol·L-1)to simulate the salinized environment by pot experiment.Analyzed the effects of salinized stress on the growth characteristics,leaf traits,underground architecture and clonal characteristics of L.chinensis.Results are as follows:1.L.chinensis had different response for different stress treatments and different treatments.With the increase of salt concentration,the biomass of per plant,leaf and underground biomass showed a decreasing tendency.But Stem biomass and plant height were increased.With the increase of alkali concentration,the growth indexes of L.chinensis were decreased.2.With the increase of salt concentration,the C/P and N/P of L.chinensis leaves increased and there was significant difference in photosynthetic rate between the middle and late growth stages.Indicated that in the face of continuous salt treatment,L.chinensis leaves could adjust in the early.But in the late,it's osmotic adjustment,photosynthesis and material accumulation and other ability were significantly disturbed.With the increase of alkali concentration,leaf area,photosynthetic rate and dry matter content of leaf showed a decreasing tendency.In the 50 mmol·L-1 alkali treatment,L.chinensis arose the lowest biomass of leaves and photosynthetic index,as well as the highest water content and the retention of a large number of C,N,P elements.Indicating that alkali stress disturbed the moisture regulation of leaves,inhibited photosynthetic capacity,reduced the synthesis of glucose,protein and other organic matter,affected the normal development of leaves and photosynthesis.3.L.chinensis by regulating the limited resources distribution,in order to achieve underground and ground collaborative development.In the 100 mmol·L-1 salt treatment,the C and N elements in rhizome and root were increased.L.chinensis balanced between underground index and adjusted clonal trait.In the case of 200 mmol·L-1salt treatment,the root diameter and volume decrease were not significant,the root length.This may be due to the fact that L.chinensis has attempted to expand its space to find favorable resources to flee the cohort environment now and to expand the sprouts for subsequent development.However,persistent salt stress treatment seriously interferes with the underground part of L.chinensis.In this environment,the nutrients and energies of the cells are not sufficient to support the rhizome continuation and development of the vegetative plants.With the increase of alkali concentration,the underground biomass and root diameter of L.chinensis were decreased,the root length,area and volume decreased significantly.The ratio of C/N and C/P increased and the root growth was seriously inhibited.In the 50 mmol·L-1alkali treatment,L.chinensis was seriously and even killed by persecution,the underground part suffered form alkali environment by the high pH and Na~+,CO3 and other anion and cation exchange replacement of the double pressure.4.Clonal components are important growth and reproduction regulation of L.chinensis.In the low concentration salt treatment,L.chinensis was used as a method for the asexual reproduction of the tiller,tiller and shoot internodes.High concentration of salt treatment,the underground buds continue to expand,but the upward output has been reduced.Indicating that L.chinensis at this time to expand the buds for breeding,but the continued salt stress treatment,serious interference with the L.chinensis clonal components,in this environment,the synthesis of nutrients and energy is not enough to support the rhizome continue to stretch and sub-strains development.With the increase of alkali concentration,the cloning of L.chinensis was increasing.The tillers and shoots,rhizomes and rhizome internodes were significantly reduced.Low concentration of alkali treatment,L.chinensis as far as possible to maintain in situ growth;high concentration of alkali treatment,L.chinensis was on the verge of death.In summary,saline-alkali stress significantly affected the growth and clonal reproduction of L.chinensis.Under low salt stress(100 mmol·L-1),L.chinensis could form salt tolerance mechanism: Regulated the chemical measurement of each part,reduce the expansion of underground roots and increase the stem and leaf output.Under the high concentration(200mmol·L-1)salt stress,L.chinensis reduced the input of leaves and various sub-strains,allocated more energy to the underground roots,taken fine root extension,increased root length,area and volume Type strategy.The effects of alkali stress on L.chinensis werelinearly related: With the increase of treatment concentration,the biomass,leaf traits,root structure and clonal traits of L.chinensis were decreased.And in the high concentration of alkali stress,L.chinensis was significantly different from that of the control group and the low concentration,even were killed.Therefore,L.chinensis individuals trade-off among the organs and within organs to cope with the stress environment.