Effect Of Urea Metabolism On Salt Tolerance Of Salix Linearistipularis

Saline-alkali land has seriously affected the normal growth and development of plants due to the high salinity and high PH in soil,resulting in the sparse vegetation on saline-alkali land and the soil deterioration.Salix linearistipularis is a small number of woody plants which are known for the normal growth and reproduction in saline-alkali land,salt-tolerance,improvement of the soil PH value and other characteristics,and they have a certain community distribution.Therefore,it is of great significance to study the salt tolerance of Salix linearistipularis.Seed germination is the key process for the normal growth and propagation of plants,and it is very important to study the effect of saline stress on seed germination after the ripening of Salix linearistipularis seeds.Therefore,this research will study the relationship between urea metabolism pathway and salt stress in the seed germination period of Salix linearistipularis.In the research,wild Salix linearistipularis seeds picked in the wild were used as experimental materials,and 1/2MS with no nitrogen(-N)and nitrogen nutrition adequacy(+N)was used as basic medium to add different concentrations of salt,and the effect of nitrogen nutrition on the germination of Salix linearistipularis seeds under salt stress was preliminarily discussed.The effects of different forms of nitrogen as the only nitrogen source on the seed germination of Salix linearistipularis were further observed in the medium containing no nitrogen(-N)under the condition of salt stress treatment.Finally,under the condition of nitrogen nutrition adequacy(+N),the key enzyme inhibitors in urea metabolism pathway were used to block the formation or further metabolism of urea,and the germination and growth of Salix linearistipularis seeds under salt stress were observed.The specific results of the study are as follows:1.Under the condition that it did not contain any nitrogen(-N),salt stress inhibited the germination of Mongolian willow seeds and the elongation of root.However,when nitrogen nutrition was sufficient(+N),the inhibitory effect of salt stress on seed germination and root elongation of Salix linearistipularis was significantly enhanced.Further by measuring the content of nitrogen metabolism related products in Salix linearistipularis under two treatments,it was found that the content of urea and NH4+in Salix linearipularis was significantly increased when nitrogen was well nourished and treated with salt stress.The presence of nitrogen can significantly enhance the inhibitory effect of salt stress on seed germination and root elongation of Salix linearistipularis.2.When urea was added to salt stress medium as the only nitrogen source,with the increase of urea addition concentration,the inhibitory effect of salt stress on seed germination of Salix linearistipularis also increased,and the product of nitrogen metabolism(especially urea metabolism)(urea and NH4+)in vivo increased significantly.When arginine was provided as the only nitrogen source,with the increase of arginine concentration,the content of urea and NH4+ in vivo increased obviously,and the addition of arginine may promote the formation and further metabolism of urea in plants,thus exacerbating the inhibitory effect of NaCl on seed germination of Salix linearistipularis.When potassium nitrate(NO3-)was used as the only nitrogen source,it had little effect on seed germination of Salix linearistipularis,and there was lo significant change in content of urea and NH4+ in vivo.However,if the ammonium chloride and ammonium nitrate(NH4+)was added as the only nitrogen sources respectively,with the increasing concentration,the inhibitory effect of salt stress on seed germination of Salix linearistipularis gradually increased,and the content of urea and NH4+ in vivo was significantly accumulated.Urea produced by urea metabolism process or its further metabolism affected the germination of Salix linearistipularis seeds under salt stress.3.The process of adding arginine inhibitors to block the production of urea by arginine decomposition under salt stress treatments also decreased the amount of urea and NH4+ content significantly.In addition,addition of urease inhibitors to block the further metabolism of urea reduces the formation of NH4+,significantly enhancing the root elongation of Salix linearistipularis under salt stress;On the contrary,if glutamine synthase inhibitors were added to block the further assimilation of NH4+,the inhibitory effect of salt stress on the elongation of Monguliugen was aggravated with the increasing concentration of addition.Therefore,the combination of the results show that blocking the formation of urea and the further metabolism of urea,or strengthening the assimilation of urea metabolites(NH4+)and reducing the NH4+ from the source of urea metabolism can significantly alleviate the inhibition of salt stress on the germination of Salix linearistipularis seeds.