Abstract:

To explore the salt tolerance mechanism of Sedum aizoon seedlings, six salt gradients including 0.2%, 0.4%, 0.6%, 0.8%, 1.0% and 1.2% NaCl were conducted to determine their influence on seedling growth, content of Na⁺, K⁺, soluble sugar, soluble protein and chlorophyll, as well as the activity of SOD, CAT and POD. The results show that significant differences on physiological and biochemical characteristics are observed among S. aizoon seedlings under different salt stress conditions. When the salt concentration is no more than 0.4%, it could promote the growth of S. aizoon, while the salt concentration reaching 1.0% could inhibit the plant growth. As the increase of the salt concentration, the Na⁺ content and the Na⁺/K⁺ ratio increase gradually, whereas the activities of SOD, CAT and POD present a first increase and then decrease trend. The soluble sugar content in plants increases significantly with the increase of the salt concentration, reaching the maximum at 0.8% concentration. A trend of the soluble protein content of first increase and then decrease is observed with the increase of salt concentration. Meanwhile, the chlorophyll content has a continuous decreasing trend with the increase of the salt concentration. Compared with 0.2% salt concentration, chlorophyll content under 0.4%, 0.6% and 0.8% is decreased by 11.5%, 50.0% and 79.9%, respectively. Overall, when the salt concentration is no more than 0.4%, it can improve the salt stress resistance by enhancing the activity of antioxidant enzymes and then promote seedling growth of S. aizoon.

Key words: Sedum aizoon, salt stress, growth, antioxidant substance, antioxidant enzyme