NaCl胁迫对不同耐盐性玉米自交系萌动种子和幼苗离子稳态的影响

盐胁迫影响植物组织的离子分布,不同品种间存在差异。以玉米耐盐自交系81162和8723及盐敏感自交系P138为材料,研究了不同浓度(0、60、140、220 mmol/L)Na Cl胁迫下萌动期种子和幼苗的不同部位中Na+、K+、Ca2+含量以及K+/Na+和Ca2+/Na+比值的变化,旨在探讨不同自交系耐盐性差异的原因。结果表明,在萌动种子中,3个玉米自交系中的Na+积累量表现为种皮胚胚乳,K+累积表现为胚种皮胚乳;幼苗中,Na+积累表现为根茎叶。随着Na Cl浓度的增加,3个玉米自交系萌动种子和幼苗中的Na+含量逐渐升高,但是萌动种子中耐盐自交系81162和8723的Na+增加幅度小于盐敏感自交系P138,Na+含量小于盐敏感自交系P138;幼苗中耐盐自交系81162和8723的Na+增加幅度大于盐敏感自交系P138,幼苗根中Na+含量大于盐敏感自交系P138;茎叶中的Na+含量小于盐敏感自交系P138。随着Na Cl浓度的增加,萌动种子和幼苗中的K+和Ca2+含量逐渐降低。K+离子在耐盐自交系81162和8723萌动种子和幼苗中的降低幅度小于盐敏感自交系P138;Ca2+离子在耐盐自交系81162和8723幼苗中的降低幅度小于盐敏感自交系P138;而在萌动种子中3个自交系Ca2+的流失差异不大。耐盐自交系81162和8723萌动种子和幼苗中K+含量都大于盐敏感自交系P138。耐盐自交系81162和8723的萌动种子和幼苗根中Ca2+含量都大于盐敏感自交系P138;幼苗叶片中则小于盐敏感自交系P138。萌动种子和幼苗中K+/Na+和Ca2+/Na+均随着Na Cl浓度的升高而降低,K+/Na+比值表现为耐盐自交系81162和8723大于盐敏感自交系P138。耐盐自交系81162和8723通过调节离子平衡维持萌动种子和幼苗中较高的K+/Na+比值从而提高耐盐性。

Ion homeostasis in germinating seeds and seedlings of three maize inbred lines under salt stress

Salt stress affects ion distribution in plant tissues. These salt-induced changes in ion distribution differ among plant varieties. In this study, we analyzed salt-tolerant inbred lines (8723 and 81162) and a salt-sensitive inbred line (P138) of maize under varying degrees of salt stress (0, 60, 140, 220 mmol/L NaCl) to explore the reasons for differences in salt resistance among the inbred lines. We measured the concentrations of Na⁺, K⁺, and Ca²⁺ in the testa, embryo, endosperm, root, stem, and leaf tissues, and determined the ratios of K⁺/Na⁺ and Ca²⁺/Na⁺ in germinating seeds and seedlings. In germinating seeds, the Na⁺ concentration was highest in the testa, followed by the embryo, and then the endosperm; the K⁺ concentration was highest in the embryo, followed by the testa, and then the endosperm. In seedlings, the highest level of Na⁺ was in the root, followed by the stem, and then the leaves; the highest levels of K⁺ were in the root and stem, followed by the leaves. With increasing NaCl concentrations in the salt treatment, the Na⁺ content increased gradually in germinating seeds and seedlings of the three maize lines. In germinating seeds, the range of the increase in Na⁺ content was smaller in the salt-tolerant lines 8723 and 81162 than in the salt-sensitive line P138, and the salt-tolerant lines accumulated less Na⁺ than did the salt-sensitive line. In seedlings, the range of the increase in Na⁺ content was larger in the salt-tolerant lines 8723 and 81162 than in the salt-sensitive line P138, and the salt-tolerant lines accumulated higher levels of Na⁺ in the roots and lower levels of Na⁺ in the stem and leaves. As the NaCl concentration in the salt treatment increased, the K⁺ and Ca²⁺ contents decreased gradually in germinating seeds and seedlings of the three maize lines. In germinating seeds and in seedlings, the salt-tolerant lines 8723 and 81162 showed smaller ranges of decreased K⁺ contents and contained higher concentrations of K⁺ compared with the salt-sensitive line P138. In seedlings, the salt-tolerant lines 8723 and 81162 showed smaller ranges of decreased Ca²⁺ contents compared with the salt-sensitive line P138. However, in germinating seeds, there was no significant difference in the range of decreased Ca²⁺ content among the three maize lines. With increasing NaCl concentrations in the salt treatment, the ratios of K⁺/Na⁺ and Ca²⁺/Na⁺ decreased in germinating seeds and seedlings. The K⁺/Na⁺ ratio was higher in the salt-tolerant lines 8723 and 81162 than in the salt-sensitive line P138. Germinating seeds and seedlings of the salt-tolerant lines 81162 and 8723 retained higher K⁺/Na⁺ ratios by adjusting ion homeostasis to improve salt resistance.