根际pH调控下景天三七对铅积累及铅胁迫的生理响应

为探索不同根际pH下,景天三七对重金属铅的忍耐指数和植株各个部位铅含量的积累规律,并找到提高植株对Pb²⁺耐受性的pH值。在不同根际pH(5、6、7、8)条件下,采用水培试验,研究景天三七在不同铅浓度(0、20、60、100、140 mg·L^-1)下对铅积累与铅胁迫的生理响应。结果表明:1)在相同pH条件下,随着铅浓度的增加,景天三七根长、株高和干质量均逐渐减小,生长受到抑制,忍耐指数逐渐下降;叶绿素含量呈现先增加后降低的趋势,谷胱甘肽(GSH)含量和超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)活性逐渐降低,MDA含量逐渐增加;根、茎、叶中铅含量随着铅浓度的增加而逐渐增加,且铅积累量表现为根>茎>叶。2)在相同Pb²⁺浓度条件下,随着pH的增加,根长、株高和干质量表现为先增加后降低的趋势;当pH=6时,植株生长较好,忍耐指数最高;忍耐指数、叶绿素含量、GSH含量和SOD、POD、CAT活性均表现出先增加后降低的趋势,且pH=6时达最大值;MDA含量变化则相反,pH=6时达最小值;根、茎、叶的铅含量逐渐降低。综上,景天三七生长受pH及Pb²⁺浓度的影响,pH影响Pb²⁺的吸收,根际pH为6时能提高植物对铅的耐受性,且Pb²⁺为20 mg·L^-1时,对铅的耐受性最强。

Physiological response of Sedum aizoon L. to lead accumulation and lead stress with different rhizosphere pH

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.