Study On Drought Resistance And Main Secondary Metabolites In Seeds Of Different Species Quinoa

Quinoa is well tolerant to adversity such as soil barrenness,salinity,drought,and frost,but there is a large difference in resistance between different species.Due to its rich nutritional,health value and potential efficacy in preventing the occurrence of various diseases.Because of this,it has received extensive attention from foreign agricultural and food scientists.Therefore,it is of great significance to study quinoa to improve the level of human support and to adjust the planting structure of agricultural crops.In this study,different concentrations of PEG-6000solution were used to simulate drought stress,and the germination indexes of five different varieties of quinoa seeds were determined to explore the germination mechanism of different varieties of quinoa seeds under different drought stress.Based on this,using potted soil culture experiments,combined with physiological and biochemical and membership function methods,to explore the drought resistance ability of different strains of quinoa.Different species of quinoa were cultivated under different drought stress conditions,and the changes of active substances and free amino acids in the seeds were determined.The results varied as following:1.Under the stress of 15%PEG,different species of quinoa seeds was inhibited.Each concentration of PEG stress decreases the growth index.In the 15%stress,the germination rates of NK1,NK2,NK3,NK4,and NK5 were 61.33%,56.00%,55.33%,54.00%and 58.67%.Compared with other varieties,the germination power of NK1 under control and 15%stress were 73.33%and 50.67%,respectively,higher than other varieties.With regard to germination index,vigor index,root length and embryonic axis length,NK5 was higher than other strains at various stress levels and showed strong drought resistance.The height increment,leaf area and biomass of each species under 15%PEG treatment were significantly lower?P<0.05?than the control.The species with the lowest increment of plant height,leaf area and biomass were NK1,NK2 and NK5,which decreased by 44.38%,25.39%and 48.23%compared with the control,respectively.2.The physiology,biochemistry and photosynthetic index of each quinoa were analyzed,and the drought resistance of quinoa was comprehensively evaluated by the subordinate function method.The drought resistance of different quinoa lines was NK5>NK2>NK1>NK4>NK3.With the increase of drought stress,the relative water content in leaves of each quinoa species decreased significantly?P<0.05?,the leaf membrane permeability,alondialdehyde?MDA?content and proline?Pro?content was increased,Pro of NK2 and NK3 were 2.69 and 1.93 times of the control under 15%PEG treatment,respectively.The activity of superoxide dismutase?SOD?,peroxidase?POD?,catalase?CAT?and ascorbic acid peroxidase?APX?were allinitially rised and then decreased.SOD,CAT and APX activity reached the maximum at 5%PEG concentration,while POD activity reached the maximum at 10%concentration treatment.With the increase of drought stress,net photosynthetic rate?P_n?,transpiration rate?T_r?and stomatal conductance?G_s?decreased.The concentration of intercellular CO₂?C_i?firstly decreased and then increased,but chlorophyll?Chl?firstly increased and then decreased.The decrease of NK5 P_n was the lowest,which was 51.15%lower than the control.3.Under moderate drought stress,the contents of total free amino acids,polyphenols,saponins and flavonoids in the seeds of various lines of quinoa were increased to varying degrees.Flavonoid synthesis upstream key enzymes?PAL,C4H,4CL?were positively correlated with flavonoid content.The antioxidant capacity of flavonoids in quinoa seeds is closely related to quinoa species and drought resistance.The total amino acid contents of quinoa cultivars reached the maximum under 5%PEG stress.NK1,NK2,NK3,NK4 and NK5 increased by 14.15%,16.99%,20.93%,18.97%and 16.13%respectively compared with CK.Drought stress significantly?P<0.05?increased the content of polyphenols and saponins in quinoa seeds,each strain of quinoa reached the maximum under 10%PEG and 5%PEG stress,respectively.With the intensification of drought stress,the content of flavonoids in the quinoa seeds increased at the beginning and then decreased,and reached the maximum at 5%PEG stress.The contents of NK1,NK2,NK3,NK4 and NK5 were 2.99,3.03 and 3.06,2.90,and 3.04 mg/g,respectively.The activities of three key enzymes?PAL,C4H,and 4CL?in the synthesis of flavonoids pathway were positively correlated with the content of flavonoids.When the flavonoids content in NK3seeds was maximal at 5%stress,the three enzymes had the highest activity.Under 5%PEG stress,flavonoids in NK3 seeds had the smallest IC₅₀ for DPPH·and·OH scavenging,which were 9.871?g/m L and 52.334?g/mL,respectively.