Exogenous treatment with salicylic acid alleviates aluminum toxicity in Camptotheca acuminata seedlings

The seedlings of Camptotheca acuminata were pre-immersed in Hoagland's solution with 10,25 mg / L salicylic acid( SA) or pre-sprayed leaves with 25,50 mg / L SA for three days,then were cultured in the presence of 1 000 mg / L Al Cl3( SA + Al) for 8 or 16 days. The seedlings exhibited a decline in fresh weight,main root length,number of lateral root,pigment content and root activity,but an increase in relative electric conductivity( REC) under Al alone treatment.However,above mentioned parameters( except REC) of seedlings were obviously up-regulated under Al treatment after pretreated with SA solution. The Al and SA + Al treatments all increased the content of camptothecin in seedlings compared to control,but the content in treatments of SA + Al was higher than that in Al alone treatment. The results showed that pretreatment with SA alleviated aluminum stress and enhanced aluminum tolerance in seedlings. The optimum treatment was 50 mg / L SA foliar spraying among four SA treatments. The treatment of 25 mg / L SA which immersed root inhibited the stem elongation,but it promoted the formation of the lateral roots and the synthesis of camptothecin in leaves and roots.