Abstract:

【Objective】We explored the effect of salt stress on the physiological characteristics, ultrastructure and content of P. cablin seedlings, which provides a reference for the artificial cultivation and stress-resistant germplasm screening of P. cablin and the cultivation of high-yield, high-quality and high-resistant varieties.【Method】Experiments were carried out with ‘Shipai’ P. cablin seedlings as materials, and salt stress was simulated by NaCl with concentrations of 0（CK）, 50（low concentration）, 100（medium concentration）, 150（middle-high concentration）and 200 mmol/L（high concentration）. Under salt stress for 10, 15 and 20 d, the leaves of P. cablin seedlings were taken to determine the antioxidant enzyme activity and malondialdehyde content, and the growth status was observed regularly. Under salt stress for 20 d, the changes of leaves’ cell structure were observed, and the contents of patchouli alcohol and patchouli ketone were determined.【Result】With the increase of salt stress concentration and the passage of stress time, the growth rate of P. cablin seedlings decreased gradually, seedlings wilted or died under high concentration salt stress. Compared with CK group, the activities of POD, CAT and the content of MDA in different concentration treatment groups increased under salt stress for 10 d，and SOD activity increased except the high concentration treatment group. The contents of patchouli alcohol and pogostone showed an upward trend, and the contents of effective components in the high concentration treatment group were higher than those in the control group under salt stress for 20 d. The results showed that the cell structure of P. cablin leaves was damaged by high concentration of NaCl stress. The chloroplast degradation was discrete, and the thylakoid stroma lamellae was slightly curved and the spacing increased. Furthermore, mitochondria cristae swelled, and some appeared semi-empty bubble appearance; the wavy plasma membrane retracted from the cell wall, and some cells separated from the plasma wall.【Conclusion】Under salt stress treatment, the antioxidant enzyme activity of P. cablin seedlings increase significantly, which can clear excess reactive oxygen species（ROS）to resist the stress environment. Meanwhile, it promoted the synthesis of patchouli alcohol and patchouli ketone of P. cablin leaves, thus to ensure plant growth and improve the quality of medicinal materials. Therefore, it is believed that P. cablin can adapt to saline soil to a certain extent.

Key words: Pogostemon cablin, salt stress, antioxidant enzymes, ultrastructure, medicinal ingredients