Abstract: In order to study the effect of salt stress on the growth and development ofPlatycodon grandiflorus, the experiment was conducted with two-year-oldPlatycodon grandiflorusas test material, four treatment groups including control (CK, normal watering), low concentration salt stress (S1, 200 mmol/L NaCl), medium concentration salt stress (S2, 400 mmol/L NaCl) and high concentration salt stress (S3, 600 mmol/L NaCl) were set up, the biomass, physiological and biochemical indexes and total saponins content ofPlatycodon grandiflorusseedlings were determined. The results showed that salt stress inhibited the growth ofPlatycodon grandiflorusand reduced its biomass with the increase of salt stress concentration, and S1 could promote the increase of chlorophyll content ofPlatycodon grandiflorus, S2 and S3 decreased the content of chlorophyll, the relative water content of leaves decreased with the increase of salt stress concentration, the activities of antioxidant enzymes in leaves and roots ofPlatycodon grandiflorusdecreased significantly at S3 and the 30th day after treatment. The contents of proline, MDA and total saponins in leaves and roots ofPlatycodon grandiflorusincreased significantly with the increase of salt stress concentration and treatment time. This study can provide a theoretical basis for improving the growth, yield and quality ofPlatycodon grandiflorusin salt-alkali soil.

Key words: Platycodon grandiflorus, salt stress, biomass, physiological indicators, total saponin