Effect of exogenous ALA、SNP and Spd on seed germination characteristics of Platycodon grandiflorum under NaCl stress

In order to get the method to improve the salt resistance of seeds and seedlings for Platycodon grandiflorum under NaCl stress,the different concentration of 5-aminolevulinic acid(ALA),sodium nitroprusside(SNP),spermidine(Spd)effect on P.grandiflorum seed germination,seed germination rate,seed germination index,and the average length of root were studied under different concentrations of NaCl stress.The results showed that the seed germination was inhibited under 75 mmol·L-1 concentrations of NaCl stress,but with different concentrations of ALA,SNP and Spd on the P.grandiflorum seeds,all germination index were significantly higher.Spd(2.5 mmol·L-1),ALA(5 mg·L-1)and SNP(0.1 mmol·L-1)could obviously alleviate the damage of salt stress to the seeds of P.grandiflorum.Spd(2.5 mmol·L-1)significantly increased all indexes.The germination vigor was 40.3%,the germination rate was 49.5%,the germination index was 9.28 and the average length of root was 2.80 cm.So we conclude that,ALA,SNP and Spd with appropriate concentration could significantly alleviate the damages to the P.grandiflorum seeds under NaCl stress and promote the salt resistance of the seeds,the best of them was Spd,the second was SNP,furthermore was the ALA.