Physiological And Ecological Responses Of Deschampsia Caespitosa Under Water Stress

Alpine marshes are important ecological security barrier in northwest China and even the whole country.Vegetation restoration and optimization of wetland plant allocation in degraded alpine marshes is a hot issue in wetland research.Alpine marshes and its edge transition zone have the characteristics of periodic waterlogging and exposure alternation,and the water condition often changes with extreme drought or waterlogging,which makes many aquatics and xerophytes difficult to grow normally.Deschampsia caespitosa can grow not only in arid environment such as grassland,but also in wet environment such as river beach and marshes.At the same time,it has the excellent characteristics of high seed yield,high germination rate,is one of the ideal degraded alpine marshes vegetation restoration species.In this study,D.caespitosa was taken as the main research object,and the comprehensive resistance of nine common alpine plants to drought/waterlogging was compared.Combined with the relationship between the population of D.caespitosa in the wild habitat and environmental factors,through the analysis of plant morphology,physiology and structural anatomy.The metabolic activities of D.caespitosa under drought,waterlogging and dry-wet alternation stress conditions were systematically revealed,which provided a certain physiological basis for the study on the adaptability of drought/waterlogging "co-tolerant" plants in alpine marshes.The main conclusions are as follows:(1)The water resistance of 9 species of alpine marsh plants was as follows: D.caespitosa,Poa crymophila,Blysmus sinocompressus,Carex moorcroftii,P.pratensis,Kobresia tibetica,Festuca sinensis,Elymus nutans,Puccinellia tenuiflora.To prove D.caespitosa is an ideal vegetation restoration material for degraded alpine marshes.(2)The widely distributed species were members of the Asteraceae,Poaceae,Cyperaceae,Ranunculaceae,Gentianaceae and Scrophulariaceae families.The multivariate analysis of community species diversity indexes,population characteristics and environmental factors showed that the % cover,height,biomass and importance value of D.caespitosa were negatively associated with species richness,Simpson dominance index,Shannon-Wiener index,soil phosphorus(P),soil moisture water(W),and positively associated with the Alatalo evenness index and soil p H.D.caespitosa was more suited to a moist to mesophytic soil environment with low P,while the importance value of D.caespitosa decreased significantly with increasing species richness in the community,indicating that D.caespitosa has some characteristics of pioneer species characteristics.(3)The resistance of D.caespitosa to water stress is closely related to its strong antioxidant defense ability and low degree of lipid peroxidation.Proline(Pro)metabolic pathway and ascorbic acid glutathione(As A-GSH)cycle are important mechanisms to improve the resistance of D.caespitosa to water stress.(4)The increase of Pro content is the result of the combined action of the strengthening of anabolism and the weakening of oxidative decomposition process.Glutamate(Glu)pathway and ornithine(Orn)pathway jointly constitute the anabolism of Pro in leaves,but the accumulation of Pro in roots is dominated by the Glu pathway.The elevated levels of As A and GSH are associated with the activation of L-galactose-1,4-lactone dehydrogenase(Gall DH)and key enzymes in the As A-GSH cycle,which initiate the efficient L-galactose-synthesis pathway and the As A-GSH cycle pathway,and maintain the higher redox state ratios(As A/DHA,GSH/GSSG).(5)Water stress did not cause significant damage to leaf structure,and its root system had certain plasticity,which was an ecological adaptation strategy to preserve life under osmotic stress,indicating that it had strong "co-tolerance" to drought and waterlogging.