Abstract:

Soil salinity is a major constraint on global agricultural production， posing a severe threat to agriculture sustainable development and food security. Maize （Zea mays L.） is one of the three major crops in China， while saline-alkali land represents a crucial reserve of arable land resources. Lignin， as a principal structural component of plant cell walls， makes it significant to study the accumulation of lignin in maize and the thickening of cell walls in response to high salinity. This study selected salt-tolerant maize inbred lines （Zhongke4M， Zheng58） and salt-sensitive maize inbred lines （PH4CV， Chang7-2） as subjects. Using a water control and a treatment of 200 mmol·L^-1 NaCl， the morphological changes and cytological characteristics of maize roots under different salt concentrations were analyzed. The differences in enzyme activity， lignin content， and gene expression were also examined. Toluidine blue staining results indicated that the reduction in the area of the root cortex and endodermis under salt stress was significantly lower in the salt-tolerant inbred lines Zhongke4M and Zheng58 compared to the salt-sensitive inbred lines PH4CV and Chang7-2. Furthermore， fluorescence microscopy observations showed that the degree of lignification in the salt-tolerant inbred lines remained stable or increased under salt stress， whereas the salt-sensitive inbred lines exhibited a decrease in lignification. The results demonstrated that the lignin content in the salt-tolerant inbred lines Zhongke4M and Zheng58 remained stable under salt stress， while it significantly decreased in the salt-sensitive inbred lines. Enzyme activity analysis revealed that under salt stress， the activity of phenylalanine ammonia-lyase （PAL） and cinnamate-4-hydroxylase （CAD） decreased in the salt-sensitive inbred lines， while the activity of cinnamate-4-hydroxylase （C4H） increased in the salt-tolerant inbred lines. RNA-seq analysis identified three genes related to lignin biosynthesis， whose expression levels varied among different maize varieties. This study provided new insights into the mechanisms by which maize responds to salt stress through the regulation of lignin accumulation and cell wall structure， contributing to the understanding of maize salt tolerance mechanisms.

Key words: maize, salt tolerance, root, cell wall, lignin

摘要：

土壤盐度是全球农业生产的主要制约因素，对农业可持续发展和粮食安全造成严重威胁。玉米（Zea mays L.）是我国三大作物之一，而盐碱地是我国极为重要的后备耕地资源。木质素作为植物细胞壁的主要结构成分，研究玉米中木质素的积累及细胞壁增厚对高盐度的响应具有重要意义。选取耐盐玉米自交系（Zhongke4M、Zheng58）和盐敏感玉米自交系（PH4CV、Chang7-2）为研究对象，采用清水对照和200 mmol·L^-1 NaCl处理，分析不同盐浓度下玉米根系的形态变化、细胞学特征，检测相关酶活性、木质素含量和基因表达的差异。甲苯胺蓝染色结果表明，耐盐自交系Zhongke4M和Zheng58在盐胁迫下根皮层和内皮层面积的减少明显低于盐敏感玉米自交系PH4CV、Chang7-2。此外，番红荧光观察显示，耐盐自交系在盐胁迫下木质化程度增强或保持稳定，而盐敏感自交系则木质化程度下降。结果表明，耐盐自交系Zhongke4M和Zheng58在盐胁迫下木质素含量稳定，而盐敏感自交系显著降低。酶活性分析显示，盐胁迫下苯丙氨酸解氨酶（phenylalanine ammonialyase，PAL）和肉桂醇脱氢酶（cinnamyl alcohd dehydrogenase，CAD）在盐敏感自交系中活性降低，而肉桂酸4-羟化酶（cinnamic acid 4-hydroxylase，C4H）在耐盐自交系中活性上升。RNA-seq分析确定了3个与木质素合成相关的基因，其在不同玉米品种中的表达量存在差异。研究结果为深入理解玉米通过调节木质素积累和细胞壁结构应对盐胁迫提供了新视角，有助于揭示玉米的耐盐机制。

关键词: 玉米, 耐盐性, 根系, 细胞壁, 木质素