Effects Of Salt Stress On Growth And Yield Of Tartary Buckwheat

The area of saline soil in China is the third largest in the world,and the area of saline soil is still increasing year by year.Soil salinization has seriously hindered the development of agriculture in our country.Tartary buckwheat is a food crop of great health value.It has the characteristics of barren tolerance,drought tolerance and short growth period,which make it can be planted in some areas with poor production conditions,and play an important role in the development,improvement and utilization of saline-alkali land.In this study,Yunqiao No.1 Tartary buckwheat with strong salt tolerance and Yunqiao No.2 Tartary buckwheat with salt sensitivity were selected as experimental materials.The effects of salt stress on carbon and nitrogen metabolism related substances and key enzyme activities,growth and yield formation of Tartary buckwheat were studied.In addition,the alleviating effect of exogenous allantoin treatment on salt stress of Tartary buckwheat was studied.The results are as follows:(1)Screening and evaluation of salt tolerance of buckwheat varietiesSixteen buckwheat varieties were treated with sodium chloride(Na Cl),sodium sulfate(Na2SO4)and sodium bicarbonate(Na HCO3).The effects of sodium chloride(Na Cl),sodium sulfate(Na2SO4)and sodium bicarbonate(Na HCO3)on germination rate,germination potential and relative damage rate of buckwheat were studied,and the salt tolerance ofbuckwheat was evaluated comprehensively.The results showed that the responses of different buckwheat varieties to Na Cl,Na2SO4 and Na HCO33 salt stress were significantly different.The germination rate,germination potential,relative germination potential and relative germination index of 16 buckwheat varieties treated with Na HCO3 were relatively low,and the inhibition effect on germination of buckwheat seeds was the most obvious.The germination of buckwheat seeds was the least inhibited by Na Cl,and the germination rates of buckwheat seeds were the same as those of control treatments.The salt tolerance of buckwheat was higher in sweet buckwheat than Tartary buckwheat.According to the results of comprehensive evaluation of salt tolerance,Jiujiang Tartary buckwheat and Yunqiao No.1 buckwheat and Ningqiao No.1 buckwheat and Guihongtian No.1 were selected as the buckwheat varieties with strong salt tolerance.These buckwheat varieties could be popularized in saline-alkali areas.(2)Effects of salt stress on carbon and nitrogen metabolism and yield of Tartary buckwheat leavesThe salt-sensitive Tartary buckwheat variety Yunqiao No.2 was treated with control(CK,0 g/kg Na Cl),low salt(S2,2 g/kg Na Cl),medium salt(S4,4 g/kg Na Cl)and high salt(S6,6 g/kg Na Cl).The changes of root morphology,contents of carbon and nitrogen metabolism related substances,enzyme activities and yield in leaves of Tartarybuckwheat under salt stress were studied.The results showed that the root length,root surface area and root volume of Tartary buckwheat increased with the growth period.The mean diameter of root,the contents of carbon and nitrogen metabolisation-related substances in leaves and the activities of related enzymes increased first and then decreased with the progress of growth period.The root activity decreased gradually with the advance of growth period.With the increase of salt stress concentration,the length,surface area,average diameter,volume and root activity of Tartary buckwheat roots,the activities of invertase,amylase,sucrose synthetase and sucrose phosphate synthetase,the contents of nitrate nitrogen,ammonium nitrogen and soluble protein,and the activities of nitrate reductase and glutamate synthetase of Tartary buckwheat leaves firstly increased and then decreased.All of them reached the maximum in S2 treatment,and the performance between treatments was: S2>CK>S4>S6;The contents of soluble sugar and sucrose and the activity of glutamate dehydrogenase in leaves increased with the increase of salt stress concentration.The number of grains per plant,100 grains weight and yield per plant of Tartary buckwheat increased first and then decreased with the increase of salt stress concentration,and the highest values were found in S2 treatment.In conclusion,moderate salt stress(2 g/kg)can promote the root growth of Tartary buckwheat,increase the content ofcarbon and nitrogen metabolism related substances and enzyme activities,and increase the yield per plant.(3)Effects of allantoin on the growth of Tartary buckwheat seedlings under salt stressThe salt-tolerant Tartary buckwheat cultivar Yunqiao No.1buckwheat and salt-sensitive Tartary buckwheat cultivar Yunqiao No.2buckwheat were treated with different concentrations of allantoin(CK,0mmol/L,0.01 mmol/L,0.1 mmol/L and 1 mmol/L)under salt stress.To study its effects on root morphology and physiology,photosynthetic pigments,leaf antioxidant enzyme activities,osmotic regulatory substances,carbon and nitrogen metabolism related substances and related enzyme activities of Tartary buckwheat seedlings.The results show that: Under salt stress,root length,volume,surface area,average diameter,root activity,contents of related substances in carbon and nitrogen metabolism and related enzyme activities,contents of chlorophyll and carotenoid,and activities of peroxidase,superoxide dismutase and catalase in leaves of Tartary buckwheat seedlings showed a trend of first increase and then decrease with the increase of exogenous allantoin concentration.All of them reached the maximum at 0.1 mmol/L treatment,and the performance between treatments was: 0.1 mmol/L > 1mmol/L > 0.01 mmol/L > CK;The contents of malondialdehyde and soluble protein in leaves of Tartary buckwheat seedlings decreasedsignificantly with the increase of allantoin concentration.In conclusion,0.1 mmol/L allantoin treatment has the best effect on alleviating salt stress and inhibiting the growth of Tartary buckwheat,and it is recommended to be used in production.(4)Effects of exogenous allantoin on carbon and nitrogen metabolism and yield of Tartary buckwheat under salt stressExogenous allantoin was sprayed at different concentrations(0,2,4and 6 mmol/L)under salt stress(4 g/kg Na Cl).The effects of exogenous allantoin on root morphology,root activity,leaf carbon and nitrogen metabolism related substances and related enzyme activities and yield of Tartary buckwheat No.2 were investigated.The results showed that the root length,root surface area and root volume of Tartary buckwheat increased with the growth period.The mean diameter of root,the contents of carbon and nitrogen metabolisation-related substances in leaves and the activities of related enzymes increased first and then decreased with the progress of growth period.The root activity decreased gradually with the advance of growth period.The root length,surface area,average diameter,volume and root activity of Tartary buckwheat,the activities of invertase,amylase,sucrose synthetase and sucrose phosphate synthetase,the contents of nitrate nitrogen,ammonium nitrogen and soluble protein,and the activities of nitrate reductase and glutamate synthetase of Tartary buckwheat leaves increased first and then decreased with the increase ofthe concentration of allantoin treatment.All of them reached the maximum at 4 mmol/L treatment.The contents of soluble sugar and sucrose and the activity of glutamate dehydrogenase in leaves increased with the increase of the concentration of exogenous allantoin.The number of grains per plant,100 grains weight and yield per plant of Tartary buckwheat increased first and then decreased with the increase of the concentration of exogenous allantoin,and the maximum value was reached at 4 mmol/L.In conclusion,exogenous allantoin treatment can alleviate the inhibition effect of Tartary buckwheat under salt stress,promote root growth,increase the content of related substances and enzyme activities of carbon and nitrogen metabolism,and improve the yield of single plant,especially 4 mmol/L treatment.