关键词: 景天三七, 根际pH, 铅胁迫, 铅积累, 生理响应

Abstract: To explore tolerance index and lead accumulating rule of Sedum aizoon seedlings with different rhizosphere pH levels under lead stress and to find the best pH at which the seedling can improve its tolerance to Pb²⁺, the multinomial physiological indexes of Sedum aizoon seedlings at different rhizosphere pH levels (5, 6, 7, 8) under different concentrations of Pb²⁺ (0, 20, 60, 100, 140 mg·L^-1) were measured. The results showed as follows: 1) Root length, plant height and dry weight all decreased with the improving of Pb²⁺ concentration at the same pH level, growth of seedlings were inhibited and tolerance index decreased, chlorophyll contents increased at first and decreased later on, content of GSH and activities of SOD, POD, CAT decreased while content of MDA increased gradually; Lead contents in root, stem and leaf gradually increased with the increase of lead concentration, and the lead accumulation were root>stem>leaf. 2) Root length, plant height and dry weight increased at first and then decreased with the improving of pH values at the same Pb²⁺ concentration; When the pH was 6, plant grew well with the highest tolerance index; Tolerance index, contents of chlorophyll and GSH, activities of SOD, POD and CAT all increased at first then decreased, and all of them reached the highest value at pH=6; However, MDA content decreased gradually, and reached the lowest value when the pH was 6; Lead contents in root, stem and leaf decreased gradually. In summary, the growth of Sedum aizoon seedling was affected by rhizosphere pH level and Pb²⁺ concentration, and absorption of Pb²⁺ was influenced by pH. When the rhizosphere pH was 6, tolerance of plant to lead could be enhanced, absorption reached the maximum when Pb²⁺ was 20 mg·L^-1.

Key words: Sedum aizoon L., rhizosphere pH, lead stress, lead accumulation, physiological response