To understand the salt tolerance mechanisms of two Glycyrrhiza species,we examined the response of root to Na⁺ and changes of vascular tissues under NaCl stress.Glycyrrhiza inflata and Glycyrrhiza uralensis seedlings were cultured with a complete Hoagland nutrient solution containing 0,50,100,150,200 and 250 mmol·L^-1 NaCl for 21 days.Then,the dry weight,root diameter,K⁺ and Na⁺ content in different parts of plants,K⁺/Na⁺ and selective absorption and transportation coefficients(SA_K,Na,ST_K,Na) were measured.The vascular tissue of root was also observed.(1)There were different effects of NaCl on seedlings of two Glycyrrhiza species.The dry weights of G.inflata and G.uralensis at 250 mmol·L^-1 NaCl were 53.34% and 46.21% that of no NaCl stress,respectively.It indicated that G.uralensis had relatively lower salt tolerance.(2)Compared with other part of plant,more Na⁺ accumulated in root of G.inflata with increased NaCl concentration,suggesting that root has good interception effect on Na⁺ that from outside salt environment.This interception effect was limited for G.uralensis because it can be only observed at 0-150 mmol·L^-1 NaCl.(3)G.inflata had more greater SA_K,Na and ST_K,Na values of root than those of G.uralensis at same NaCl concentration,implying a stronger selective transport capability for K⁺ of root while Na⁺ was inhibited from being transported to stem.For these reasons,the significant difference of salt tolerance occurred in two Glycyrrhiza species.(4)The ratio of vascular tissue area to total root area of G.inflata and G.uralensis were increased at 250 mmol·L^-1 and 150-200 mmol·L^-1 NaCl,respectively.It displayed the root anatomical adaptation,which contributes to enhancement of transportation capability of root and alleviation of salt injury.