Physiological Response Of Lycium Barbarum To Saline Stress And Alkali Stress

With the rapid development of industry and agriculture and increasing population,soil salinization of Qaidam basin is more and more serious,and has become a conditionality factor of economic sustainable development and ecological environment security.In this study,the most important economic species in Qaidam Basin Lycium barbarumis is research object.Pot control experiment was carried out on Nuomuhong farm in the southeastern margin of Qaidam Basin.NaCl and NaHCO3 were imposed on plant to simulate saline-alkali land,maintaining the optimum moisture content for growth,and then set 0,50,100,200 and 300 mmol·L-1 4 concentration gradient.The response of Lycium barbarum under salt and alkali stress was studied,and based on the analysis of the difference of growth index,photosynthetic system and antioxidant enzyme system index under two treatments,using regression analysis to calculate the salt tolerance threshold and alkali resistance threshold of Lycium barbarum.Reveal the physiological mechanism of Lycium barbarum.Main conclusionsareelicitedasfollows:(1)Low concentration of NaCl stress had no significant effect on the growth of Lycium barbarum,with the increasing salt concentration,the height growth,water content,biomass and relative growth rate decreased significantly,The water deficit is significantly increased and the distribution of biomass is changed;under alkaline stress,height growth,water content,biomass and relative growth rate declined even more sharply,Water deficit and biomass allocation were more serious;The inhibitory effect of alkali stress on the growth was stronger than salt stress;(2)The content of chlorophyll,net photosynthetic rate,transpiration rate and stomatal conductance were decreased under saline and alkali stress,those index declined even more sharply under alkaline stress.The inhibitory effect of alkali stress on photosynthesis was stronger than that of salt stress;The critical value of stomatal limitation and non stomata]limitation was analyzed through the change of intercellular carbon dioxide concentration.The critical concentration of salt stress was 200 mmol·L-1,and the critical concentration of alkali stress was 100 mmol·L-1;(3)Through the hyperbolic fitting,The results showed that Pnmax,RD,AQY and LSP of Lycium barbarumunder stress were lower than control group,and decreased with the increase of concentration,the magnitude of the decline under alkali stressis greater;The LCP of Lycium barbarumunder salt and alkali stress was both higher than that of control group,and the increase under alkali stress is greater;(4)The content of MDA under alkali stress was higher than that under salt stress,the results showed that the alkali stress was more destructive to the integrity;Under salt stress,SOD,POD,CAT and other enzymes increased with the increase of salt concentration;the activities of SOD,POD and CAT increases first and then decreases under alkali stress,200 mmol·L-1 is a turning point from high to low.This indicates that 200 mmol·L-1 is the limit of the regulation of antioxidant system under alkali stress.(5)By regression analysis,in accordance with the standards of index more than 50%in the control group,the salt tolerance threshold was 241.5 mmol·L-1 and the alkali resistance was 108.4 mmol·L-1.The threshold of alkali resistance of Lycium barbarum was much lower than salt tolerance,This indicated that alkali is more destructive than salt stress.