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Large quantities of deicing salts are applied in urban areas for clearing the pavement and ensuring the normal traffic flow during the winter seasons in northeastern China.The salt from deicing operation has been observed to accumulate in roadside soil and inhibit the growth of vegetation.It was reported that the application of exogenous K+ and salicylic acid(SA) could protect plants against abiotic stress.In this study,pot experiments were performed in soil culture to test the efficacy of two soil additives,potassium nitrate(KNO3) and SA,in alleviating the stress of deicing salts on growth and photosynthetic parameters of Pinus tabulaeformis seedlings.Three soil additive levels were used i.e.10,20,40 mmol/L for KNO3 and 2,4,8 mmol/L for SA,respectively,under the stress of 0.2% deicing salts per dry weight of soil.After the treatment for 20 days(d),relative water content,leakage rates of electrolyte,malondialdehyde(MDA),peroxidase(POD) and chlorophyll content in leaves were determined.Dry weight of roots,stems and leaves were measured respectively after 60 d of treatments.Three important parameters of photosynthesis,photosynthetic rates(Pn),intracellular CO2 concentrations(Ci) and stomatal conductance(Gs) were measured every 7 d until 35 d. The results showed that the growth of seedlings was inhibited significantly by the stress of 0.2% deicing salts.The dry weight and relative water content of roots,stems and leaves under 0.2% deicing salt stress were decreased significantly in comparison with the control seedlings.The leaves of Pinus tabulaeformis were more sensitive to the stress of deicing salts compared with roots and stems.However,the treatment of 20 mmol/L KNO3 and 2mmol/L SA to 0.2% deicing salts had high dry weight and water content.Meanwhile,the MDA content and leakage rates of electrolyte increased once exposure to 0.2% deicing salts,and salts exposure also had an inhibitory effect on the activities of the POD.However,with the addition of 20 mmol/L KNO3 and 2 mmol/L SA,the high stability of membrane was improved by promoting the POD activities,with decreasing plasmalemma permeability and MDA content in leaves.On the other hand,the contents of Pn,Ci,Gs and the chlorophyll all decreased in the Pinus tabulaeformis seedlings by the treatment of 0.2% deicing salts.The addition of 20 mmol/L KNO3 significantly increased photosynthetic rates from 5.77% to 20.6% with the prolonging of the exposure time.However,other treatments were found no obvious alleviation effect.It was also found that the contents of Ci and Gs remained unchanged in leaves of Pinus tabulaeformis seedlings in all alleviation treatments,but the enhancing of chlorophyll contents played a key role in maintaining the leaf photosynthetic rate under the treatment of KNO3 and SA.The results indicated that the salt tolerance of Pinus tabulaeformis seedlings was improved by using soil additives of 20 mmol/L KNO3 and 2 mmol/L SA.Exogenous K+ and SA showed strong benefits against deicing salts-induced negative symptoms.