野皂荚对NaCl胁迫的生理响应及耐盐性

以盆栽野皂荚2年生实生苗为材料，设置土壤NaCl含量分别为0.053%（CK）、0.15%、0.3%、0.45%和0.6%的盐胁迫处理，研究不同浓度盐处理对苗木生长、细胞膜透性、细胞保护酶活性以及Na⁺和K⁺分布格局的影响,探讨了其耐盐阈值和机理.结果表明：随着NaCl浓度增加，苗木生长量逐渐降低，盐害指数逐渐升高；野皂荚可忍耐的土壤含盐量为0.42%.随着NaCl浓度增加，叶片相对电导率、氧自由基产生速率和丙二醛(MDA)含量均逐渐增大；超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活性呈先上升后下降的变化趋势，在土壤含盐量0.3%或0.45%时达到峰值；高盐胁迫下，SOD、POD和CAT活性的增强可及时清除盐胁迫产生的氧自由基，进而缓解或避免膜脂过氧化作用对组织细胞的伤害.盐胁迫下根、茎、叶的Na⁺含量均逐渐增大，且呈现根>叶>茎的分布格局；K⁺含量和K⁺/Na⁺呈下降趋势，呈现叶>根>茎的分布格局；K⁺-Na⁺选择性运输系数(S_K⁺·Na⁺)随着土壤含盐量的增加逐渐升高，且叶S_K⁺·Na⁺高于茎S_K⁺·Na⁺.野皂荚耐盐机制是根系拒盐和叶片耐盐；盐胁迫下，根系Na⁺累积能力增强可控制Na⁺向地上运输以避免盐害发生，叶片K⁺选择性吸收和累积能力的显著提高可忍耐和补偿Na⁺对组织的伤害.

Physiological response and salt tolerance of Gleditsia microphylla under NaCl stress.

In order to exploit the salt tolerance ability and mechanism of Gleditsia microphylla, the plant growth, cell membrane permeability, the activities of cell protective enzymes, and the distributions of Na⁺ and K⁺ in different tissues were investigated under various NaCl stress (0.053%, 0.15%, 0.3%, 0.45% and 0.6%) with potted two year seedlings. The results were as follows: With the increase of NaCl concentration, the seedling growth decreased while the salt injured index increased, and the salt tolerance thresholds of seedling was 0.42% NaCl. With the NaCl concentration increasing, the membrane permeability, superoxide anion radical generating rate and MDA content increased grandly, while the activities of SOD, POD and CAT demonstrated an increase decrease curve which reached the peak at 0.3% or 0.45%. Under the high salt stress condition, the supero xide anion could be consumed timely by increasing the activities of SOD, POD and CAT enzymes, which was useful to avoid cell injure. Under salt stress condition, the Na⁺ content in different tissues increased gradually, following the order of root > leaf > stem, and the K⁺ content and K⁺/Na⁺ in different tissues decreased, following the order of leaf > root > stem. The K⁺-Na⁺ selective transportation coefficients (S_K⁺·Na⁺) of stem and leaf tissues under the soil NaCl stress condition were both increased, following the order of leaf > stem. In conclusion, the findings suggested that the salt adaptation mechanisms of G. microphylla were root salt rejection by Na⁺ accumulation and restriction in root tissue and leaf salt tolerance by a remarkably increased ability of K⁺ selective absorption and accumulation in leaf tissue.