The Physiological Response Of Chenopodium Quinoa Willd.to Saline Alkaline Stress In The Early Stage Of Growth

Soil alkalization is one of the most important factors that inhibit plant growth and reduce crop yield and quality.At present,planting of halophytes is an effective measure to improving and utilizing saline-alkali soil.As one of the salt tolerant crop,quinoa（Chenopodium quinoa Willd.）can be promoted in saline and alkaline environments.Though there were many studies on the salt tolerance mechanism of quinoa,most of them focused on the vegetative growth period,the effect of saltine alkaline stress in the early growth stage of quinoa has not been studied extensively.Based on this,this paper analyzed the effects of different concentrations of saline alkaline stress the germination and physiological metabolism parameters of seedlings of quinoa in the early stage of growth,these information should help reveal more insights on the tolerance of salt-alialine stress of quinoa,and then elucidated the salt-tolerance situation during the germination phase of quinoa,in order to provide theoretical basis for the cultivation of quinoa under saline-alkali environment.In this study,quinoa was treated with three different salts:the quinoa seeds were germinated and grown in Petri dishes with neutral salt NaCl（0,50,100,200,300 mM）,alkaline salt NaHCO₃（0,50,100,150,200 mM）and mixed salt（NaCl:NaHCO₃=1:1）（0,50,100,150,200 mM）respectively.The experiment was divided into seed germination stage and seedling growth stage.In the first stage,the germination rate,time to 50%germination,germination index and seedling vigor index four indicators were determined to analysed the response of seed germination stage of quinoa to salt-alkaline stress.In the second stage,osmoregulation（cation,anion,organic acid,proline）,soluble sugar,and antioxidant capacity（SOD,CAT,POD,MDA）was determined to analysed the response of seedling growth stage of quinoa to salt-alkaline stress.The experimental results and conclusions was as follows:In the seed germination stage,the seed germination of quinoa was delayed significantly in the low concentration of salt-alkaline stress,while the seed germination of quinoa was obviously inhibited by the high concentration of NaCl stress.The seeds of quinoa weren’t germinated under high Na Cl stress,which could avoid the harm of high concentration salt stress;while quinoa seeds could germinate in the high concentrations of NaHCO₃ and mixed salt stress,but the seedling vigor after germination was significantly reduced,and seriously affected the growth of quinoa seedlings to some extent.Seedling growth stage:quinoa could accumulate Na⁺and Cl^-to maintain the balance of intracellular osmotic balance in NaCl stress;Na⁺and organic acids（oxalic acid,citric acid and malic acid）were accumulated to maintain osmotic potential and pH stability under NaHCO₃ stress;quinoa accumulated Na⁺,Cl^-and organic acids（oxalic acid,citric acid and malic acid）,and they worked togeter to alleviate salt-alkaline stress in mixed salt stress.Proline has little effect on the saline alkaline process in the early growth stage of quinoa,and the main reason may be that the energy consumption for synthesizing organic osmotic substances was relatively large.In the early stage of growth of quinoa,carbohydrate metabolism had been less affected at low concentrations of saline alkaline stress,and its hydrolysate（soluble sugars）could participate in osmoregulation and provide energy for cell metabolism.However,the carbohydrate metabolism was inhibited at high concentrations of saline alkaline stress,and the hydrolysate（soluble sugars）had no obvious effect on seeds germination and osmoregulation.SOD and CAT activities increased of quinoa in NaCl stress,and they increased the salt tolerance of quinoa.SOD and CAT activity remain unchanged under mixed salt stress,which could reduce the damage of salt stress to some extent.However,NaHCO₃ stress significantly reduced the activity of antioxidant enzymes,causing a large accumulation of intracellular ROS,leading to more severe oxidative stress.In summary,When the seeds germinated,under NaCl stress,quinoa could avoid the harm of salt stress by delaying germination and maintaining dormant state;NaHCO₃ and mixed salt stress had less effect on the final germination rate of quinoa,but it will seriously damage the vitality of quinoa seedlings.But after the seeds germinated,Under NaHCO₃ stress,quinoa mainly relied on the accumulation of Na⁺and organic acids to resist the salt-alkali stress.At this time,the quinoa seedling had the greatest degree of damage;the quinoa seedling under mixed salt stress could through osmotic regulated,accumulated organic acids,and maintained antioxidant enzyme activity at the same time to relieve saline-alkaline stress,quinoa seedling had less damage.Under Na Cl stress,quinoa could ensure the normal development of seedling through osmotic adjustment and increase of antioxidant enzyme activity,quinoa seedling had the least damage.