The Regulating Physiological Mechanism Of Exogenous Nitric Oxide On Salt-Resistance Of Reaumuria Soongorica

Nitric oxide（NO）is a vital molecular biological signal,it is participated in various physiological processes of plant growth and development,and is closely related with plant form,antioxidant regulation,material metabolism and programmed cell death.NaCl will not only inhibit the growth of plants,but in severe cases will cause their death.Reaumuria soongorica is a dominant species and it’s habitat are concentrated in a large number of saline-alkali areas in northwestern China.It’s growth community establishment is of great significance to the ecology of this region of China.NaCl can be effect on both seed generation stage and seedlings growth,which has an important impact on the stability of vegetation communities and vegetation regeneration in its habitat.In this study,R.soongorica were used as the research material to study the regulation mechanism of exogenous NO on the growth,physiological characteristics,carbon metabolism and nitrogen metabolism of R.soongorica under NaCl stress,which were used to explain the NaCl tolerance of NO to R.soongorica from a physiological perspective,and provided a theoretical basis for improving the regeneration of R.soongorica communities in desert areas and improving saline-alkali land.The main results were as follows:1.The fresh weight,dry weight,plant height and root-shoot ratio of R.soongorica were significantly reduced under NaCl stress.Shoot fresh and dry weight,root fresh weight and dry weight and plant height of R.soongorica first increased and then decreased with NO concentrations increased under NaCl stress.This showed that NO can alleviate the inhibitory effect of NaCl stress on the growth of R.soongorica.2.NaCl stress reduced the net photosynthetic rate of R.soongorica leaves,and reduced stomatal conductance and transpiration,and had no significant effect on photosynthetic pigments.The effect of NO can significantly increase the content of chlorophyll a,chlorophyll b,total chlorophyll,carotenoids,and increase the stomatal conductance and transpiration of leaves to improve its net photosynthetic rate.NaCl stress also caused MDA contents increasing,changed antioxidant enzymes activities,and increased Na⁺/K⁺rate,the ion selective transport capacity also reduced.The effect of NO can increase SOD,POD and CAT activities,reduce the MDA content,and increase the selective transport of ions in R.soongorica.This showed that NO can alleviate the effects of NaCl stress by increasing the R.soongorica ROS system and absorption of nutrients.3.Soluble sugar and sucrose concentrations in leaves and soluble sugar and starch concentrations in roots both decreased significantly,SPS（Sucrose Phosphate Synthase）activities in leaves,SS（Sucrose Synthase）and SPS activities in root both decreased,AI（Acid Invertase）and NI（Neutral Invertase）activities both increased in R.soongorica roots under 300 mmol·L^-1 NaCl stress.Exogenous NO can significantly increase soluble sugar and sucrose concentrations in R.soongorica roots and leaves,and increase SS,SPS,AI,and NI activities in leaves,and decrease SS,AI and NI activities in roots under NaCl stress.4.GS,GOGAT and NR activities,soluble protein and NO₃^-N concentrations both decreased significantly under 300 mmol·L^-1 NaCl stress.Exogenous NO can significantly increase Gs,GOGAT,NR activities and nitrate nitrogen concentrations in R.soongorica roots and leaves,and increase soluble protein and free amino acid concentrations in roots.5.Based on various indicators were comprehensive analyzed,NO has the largest contribution to photosynthetic indicators in the relief of R.soongorica under NaCl stress,followed by nitrogen metabolism and growth indicators.0.10 mmol·L^-1SNP was the most effective for alleviating NaCl stress in R.soongorica,followed by 0.01mmol·L^-1SNP,and over 0.25 mmol·L^-1SNP was not effective for alleviating NaCl stress in R.soongorica.