盐胁迫对槲树(Quercus dentata)幼苗离子平衡及其生理生化特性的影响

检测NaCl胁迫对槲树（Quercus dentata）幼苗离子平衡和生理生化特性的影响，为揭示槲树的耐盐机理，其在园林中的推广应用提供参考。以一年生槲树实生苗作为实验材料，经100、200、300 mmol/L的NaCl溶液浇灌处理30 d，测定不同时间的离子含量和生理生化指标变化。结果表明，随NaCl浓度的增加和处理的时间延长，槲树各指标表现出以下规律：（1）根茎叶积累大量Na⁺，引起离子毒害，导致叶片受损，根系Na⁺含量显著高于地上部分，这种补偿作用有助于减轻地上部分受到的损害；（2）各部分K⁺含量降低，根部较茎叶更为显著，导致Na⁺/K⁺明显升高；（3）Ca²⁺由根部向地上部分转运，在叶片中浓度显著增加，有助于建立新的离子稳态；（4）Mg²⁺含量总体上呈降低趋势；（5）叶片含水量逐渐降低，丙二醛含量和相对电导率逐步升高，且在重度胁迫下的变化更显著；（6）轻度盐胁迫下，叶片过氧化物酶（POD）活性无显著变化，而过氧化氢酶（CAT）和超氧化物歧化酶（SOD）活性逐渐升高，在重度胁迫下3种酶活性出现降低；（7）脯氨酸和可溶性糖少量积累，辅助调节渗透平衡。总之，槲树幼苗能够通过调控离子平衡，提升抗氧化酶活性，积累渗透调节物，从而提高耐盐性，抵御200 mmol/L以下的NaCl胁迫。

Effects of salt stress on the ion balance and physiological-biochemical characteristics of Quercus dentata seedlings

The effects of NaCl stress on ion balance and physiological and biochemical characteristics of Quercus dentata seedlings were tested to provide reference for understanding the salt tolerance mechanism and the application in landscape architecture. One year old seedlings of Q. dentata were used as plant materials, and were treated with 100 mmol/L, 200 mmol/L, and 300 mmol/L NaCl solutions for 30 days through Irrigation. The changes of ion contents and physiological and biochemical indexes were measured at different time. The results showed that with the increase of NaCl concentration and the prolongation of treatment time, the indexes of seedlings showed the following rules: (1) a large amount of Na⁺ was accumulated in roots, stems, and leaves, which caused ion toxicity, leading to leaf damage. And the Na⁺ contents of roots were significantly higher than that of aboveground parts, which was helpful to reduce the damage of aboveground parts; (2) the K⁺ contents of each part decreased, and in the roots the decreased degree was more significant than that in stems and leaves. This resulted in significant addition of Na⁺/K⁺; (3) Ca²⁺ transported from roots to the aboveground parts, and the contents of Ca²⁺ in leaves increased significantly, which helped to establish a new ion homeostasis; (4) The Mg²⁺ contents presented decreased trend on the whole; (5) the water content of leaves decreased gradually, and the content of malondialdehyde and relative conductivity increased gradually. And the change was more significant under severe stress; (6) Under mild salt stress, the activities of peroxidase (POD) did not showed obvious change, and the activities of catalase (CAT) and superoxide dismutase (SOD) increased gradually. Tut the activities of three enzymes decreased under severe stress; (7) The contents of proline and soluble sugar accumulated in a small amount to help regulate osmotic balance. In sum, Q. dentata seedlings can improve salt tolerance by regulating ion balance, enhancing antioxidant enzyme activity, and accumulating osmotic regulators. The Q. dentata seedlings can resist NaCl stress below 200 mmol/L.