The growth and development of maize is affected in a crucial way by the salinity of the soil it grows in. Therefore, if we want to improve the salt tolerance of maize, it is of paramount importance to understand how it responds to salt stress. To explore how maize adapts to a saline environment, we chose one salt-tolerant maize variety, Jingnongyu 658 (JNY658), and one salt-sensitive variety, Yunyu7 (YY7), and treated the seedlings of both varieties with a 100 mM NaCl solution. After harvesting them, we analysed the adaptive responses to salt stress with respect to various characteristics of the root architecture and water and nutrient acquisition. We found that when subjected to salt stress, both varieties exhibited a reduction in biomass, root activity, ¹⁵N and H₂¹⁸O uptake amount, lateral root branching density, lateral root length, total root length, root surface area and root volume, where the YY7 suffered a greater reduction than the JNY658. Salt stress also induced a decreased absorption of K⁺, passively promoted the absorption of Na⁺ and gave rise to an increased Na⁺/K⁺ ratio in the roots of both varieties. It should be noted that JNY658 exposed to salt stress developed a lower Na⁺/K⁺ ratio than YY7. Compared with the control group, the expression of ZmSOS1, ZmSOS2 and ZmNHX genes in the roots of JNY658 subjected to salt stress was significantly upregulated, which enabled them to maintain a lower Na⁺ content. In both varieties, the salicylic acid (SA) and gibberellin₁₉ acid (GA₁₉) content increased significantly, but the auxin (IAA), jasmonic acid (JA) and trans-zeatin (TZ) content was reduced. In addition, JNY658 in salt stress significantly increased their abscisic acid (ABA) content, due to the increased expression of its key biosynthesis genes, NCED. Compared with JNY658, the reductions in IAA, JA and TZ content in YY7 were greater, while the increases in ABA and SA content were smaller. The varieties in the ABA, JA, SA and IAA of roots subjected to salt stress significantly or extremely significantly correlated with the lateral root branching density, lateral root length, root surface area, Na⁺ content, K⁺ content and Na⁺/K⁺ ratio. We conclude that the salt-tolerant maize variety mitigated the toxic effect of salinity on maize root growth and development by regulating the hormone content and enhancing its expression of stress-responsive genes while maintaining ion homeostasis and promoting water and nutrient acquisition, which ultimately resulted in a less pronounced decrease in plant biomass.

中文翻译：

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内源性激素通过诱导根结构和离子平衡优化来提高玉米 (Zea mays L.) 的耐盐性

玉米的生长发育受到其生长土壤盐分的重要影响。因此，如果我们想提高玉米的耐盐性，了解它对盐胁迫的反应至关重要。为了探索玉米如何适应盐碱环境，我们选择了一种耐盐玉米品种景农玉658（JNY658）和一种盐敏感品种云玉7（YY7），并用100 mM NaCl溶液处理这两个品种的幼苗. 收获它们后，我们分析了对盐胁迫的适应性反应，涉及根结构的各种特征以及水分和养分的获取。我们发现，当受到盐胁迫时，两个品种的生物量、根系活性、¹⁵ N 和 H ₂ ^18均降低O吸收量、侧根分枝密度、侧根长度、总根长、根表面积和根体积，其中YY7比JNY658下降幅度更大。盐胁迫还导致两个品种根系对K ⁺的吸收减少，被动促进对Na ⁺的吸收，并导致Na ⁺ /K ^{+比值增加。}需要注意的是，JNY658 在盐胁迫下的 Na ⁺ /K ⁺比值低于 YY7。与对照组相比，盐胁迫下JNY658根系中ZmSOS1、ZmSOS2和ZmNHX基因的表达显着上调，使其能够维持较低的Na ⁺内容。两个品种水杨酸（SA）和赤霉素₁₉酸（GA ₁₉）含量均显着增加，而生长素（IAA）、茉莉酸（JA）和反式玉米素（TZ）含量降低。此外，由于其关键生物合成基因 NCED 的表达增加，盐胁迫下的 JNY658 显着增加了其脱落酸 (ABA) 含量。与JNY658相比，YY7中IAA、JA和TZ含量的降低幅度较大，而ABA和SA含量的增加幅度较小。根系ABA、JA、SA和IAA中盐胁迫的品种与侧根分枝密度、侧根长度、根表面积、Na ⁺含量、K ⁺含量和Na⁺ /K ⁺比率。我们得出结论，耐盐玉米品种通过调节激素含量和增强其应激反应基因的表达，同时保持离子稳态和促进水分和养分的获取，从而减轻盐分对玉米根系生长和发育的毒性作用，最终导致植物生物量的减少不那么明显。