Adaptive Mechanism To NaHCO₃ Stress In Chenopodium Quinoa Willd

Soil salinization has become the important abiotic limiting factor on crop yields.It has proved that salt stress and alkali stress are different types,which have different effects on plants.The harm of alkali stress on plant is more serious than salt stress.In recent years,people gradually pay attention to the damage effect of alkali stress on plants,as well as the mechanism of plant resistance to alkali stress.Quinoa is the ancient crop in the Andes of South America,which is rich in nutritional value,and has strong ability to adapt various extreme environments.The salt resistance mechanism of quinoa has been widely studied,but the effect of alkali stress and the alkali resistance mechanism have not been widespread explored.So,growth parameters,photosynthesis,antioxidant enzyme activity and osmotic adjustment ability were investigated under the different concentrations of NaHCO₃ stress.Such information should help reveal more insights on the alkali resistance mechanisms of quinoa,and provide theoretical basis for the cultivation of quinoa under alkali stress environment.As a kind of facultative halophytes,quinoa was chosen as the study material.The alkaline salt?NaHCO₃?was used to simulate different strength of alkali stress environment.Four concentrations were applied: 50,100,150 and 200 mM.The growth indexes?RGR,RWC,FW:DW,root-shoot ratio?,photosynthetic indexes?Pn,Tr,gs,Ci,stomatal density,contents of photosynthetic pigment?,antioxidant enzyme activities?SOD,POD,CAT,MDA?,and osmoregulation contents?proline,soluble sugar,cationic,anionic,organic acids?were determined,to analyze the response of quinoa to NaHCO₃ stress.The results showed that chlorophyll content was not significantly changed,and stomatal factors had little effect on photosynthesis under low concentrations?50-100 mM NaHCO₃?stress.Therefore,quinoa could maintain high photosynthetic rate.In addition,CAT and POD activity increased significantly,removing the excess free radicals,maintaining the balance of active oxygen metabolism and membrane system stability effectively,reducing the oxidative stress on quinoa.The K+/Na+ kept relatively stable under the stress treatments group,to meet the metabolic needs of quinoa.Organic acids played an important role in the maintenance of ion balance and pH stability.In order to adjust the osmotic balance,most substances and energy were used for the synthesis and accumulation of organic osmotic regulators,resulting in biomass on the ground parts reduced,so that the RGR decreased.Under the higher concentration of NaHCO₃ treatments,the contents of Mg2+ and chlorophyll were decreased obviously,the non-stomatal factors significantly affected the photosynthetic capacity of quinoa.This resulted in the growth of quinoa was significantly inhibited.Simultaneously,the activity of CAT decreased,while POD continued to play an important role in the removal of reactive oxygen species,to maintain cell metabolism.Proline and soluble sugar played an important role in osmotic regulation under high intensity stress,to alleviate the harm of NaHCO₃ stress on quinoa.The adaptability mechanism of quinoa under high concentrations of NaHCO₃ stress led to a further decrease in the growth of quinoa,but seedlinds could continue to survive,which indicated that quinoa had strong resistance to NaHCO₃ stress.