Liu Jia, Shao Yang, Feng Xiaohui, Otie Victoria, Matsuura Asana, Irshad Muhammad, Zheng Yuanrun, An Ping
Arid Land Research Center, Tottori University, 1390, Hamasaka, Tottori 680-0001, Japan.
College of Plant Science & Technology, Huazhong Agricultural University, Wuhan 430070, China.
Plants (Basel). 2022 Mar 28;11(7):900. doi: 10.3390/plants11070900.
Understanding the role of root cell walls in the mechanism of plant tolerance to salinity requires elucidation of the changes caused by salinity in the interactions between the mechanical properties of the cell walls and root growth, and between the chemical composition of the cell walls and root growth. Here, we investigated cell wall composition and extensibility of roots by growing a halophyte () and a glycophyte () species under an NaCl concentration gradient. Root growth was inhibited by increased salinity in both species. However, root growth was more strongly reduced in than in . Salinity reduced cell wall extensibility in significantly, whereas treatment with up to 200 mM NaCl increased it in . Meanwhile, root cell walls exhibited relatively high cell wall stiffness under 300 mM NaCl treatment, which resist wall deformation under such stress conditions. There was no decrease in pectin content with salinity treatment in the cell walls of the elongation zone of roots. Conversely, a decrease in pectin content was noted with increasing salinity in , which might be due to Na accumulation. Cellulose content and uronic acid proportions in pectin increased with salinity in both species. Our results suggest that (1) cell wall pectin plays important roles in cell wall extension in both species under salinity, and that the salt tolerance of glycophyte is affected by the pectin; (2) cellulose limits root elongation under saline conditions in both species, but in halophytes, a high cell wall content and the proportion of cellulose in cell walls may be a salt tolerance mechanism that protects the stability of cell structure under salt stress; and (3) the role of the cell wall in root growth under salinity is more prominent in the glycophyte than in the halophyte.
要理解根细胞壁在植物耐盐机制中的作用，需要阐明盐分对细胞壁机械性能与根生长之间相互作用以及细胞壁化学成分与根生长之间相互作用所造成的变化。在此，我们通过在NaCl浓度梯度下培养一种盐生植物（）和一种甜土植物（）来研究根的细胞壁组成和伸展性。两种植物的根生长均受盐分增加的抑制。然而，[甜土植物]的根生长受抑制程度比[盐生植物]更强。盐分显著降低了[甜土植物]的细胞壁伸展性，而高达200 mM NaCl的处理却增加了[盐生植物]的细胞壁伸展性。同时，[盐生植物]的根细胞壁在300 mM NaCl处理下表现出相对较高的细胞壁刚度，可在这种胁迫条件下抵抗细胞壁变形。[盐生植物]根伸长区细胞壁的果胶含量在盐分处理下并未降低。相反，[甜土植物]中果胶含量随盐分增加而降低，这可能是由于钠积累所致。两种植物中果胶的纤维素含量和糖醛酸比例均随盐分增加而升高。我们的结果表明：（1）细胞壁果胶在两种植物盐分条件下的细胞壁伸展中起重要作用，甜土植物的耐盐性受果胶影响；（2）纤维素在两种植物盐分条件下均限制根伸长，但在盐生植物中，高细胞壁含量及细胞壁中纤维素比例可能是一种耐盐机制，可在盐胁迫下保护细胞结构稳定性；（3）细胞壁在盐分条件下对根生长的作用在甜土植物中比在盐生植物中更突出。
