Chitosan Soaking Improves Seed Germination of Platycodon Grandiflorus and Enhances Its Growth, Photosynthesis, Resistance, Yield, and Quality

Abstract

Platycodon grandiflorus is a medical, ornamental, and edible traditional Chinese medicine whose seed germination and plant growth are frequently restricted by dormancy and stresses. In this study, we investigated how chitosan soaking affected seed germination, growth, photosynthesis, resistance, yield, and quality of P. grandiflorus. The results indicated that chitosan soaking had a preferable enhancing effect on seed germination of P. grandiflorus, which significantly (p < 0.05) promoted its germination rate, energy, and index, as well as cotyl and radicle length. Furthermore, 0.15–0.20% chitosan soaking effectively enhanced the leaf growth, height, stem diameter, and overground part dry weight of P. grandiflorus and reliably improved their leaves’ chlorophyll, photosynthetic rate, transpiration rate, and water use efficiency. Moreover, 0.15–0.20% chitosan soaking effectively enhanced the stress resistance and adaptability of P. grandiflorus via increasing its resistance substances and triggering its defense enzyme activity. Meanwhile, 0.15–0.20% chitosan soaking effectively improved the underground part growth and medical quality of P. grandiflorus. This study highlights that chitosan can be used as a favorable, efficient, and economical candidate or promoter for enhancing seed germination of P. grandiflorus and improving its growth, photosynthesis, resistance, yield, and quality; it also highlights that 0.15–0.20% chitosan is a suitable concentration.