Guo Jiuxin, Jiao Yiling, Wang Yuwen, Hu Wenlang, Jia Yamin, Huang Zengrong, Yang Lin-Tong, Chen Li-Song
Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, International Magnesium Institute, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, 350002, China.
Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, International Magnesium Institute, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, 350002, China.
Plant Physiol Biochem. 2023 Nov;204:108146. doi: 10.1016/j.plaphy.2023.108146. Epub 2023 Oct 26.
Magnesium (Mg) and calcium (Ca) are two essential macronutrients in plants; however, the characteristics of Mg and Ca concentrations in organ, subcellular and chemical forms and their relationships in citrus plants, especially under varying Mg supply, are not well understood. In this study, Citrus sinensis seedlings (cv. Xuegan) were cultivated in conditions of Mg deficiency (0 mmol Mg L) and Mg sufficiency (2 mmol Mg L) to investigate the responses of Mg and Ca homeostasis in different organs and fractions. Compared with Mg sufficiency, Mg deficiency significantly decreased root and shoot growth, with the shoot biomass reduction of branch organs was greater than that of parent organs. In addition to increasing the Ca concentration in the parent stem and lateral root organs, Mg deficiency significantly decreased the concentrations and accumulations of Mg and Ca in citrus seedlings, further altering their distribution in different organs. More than 50% of Ca and Mg were sequestrated in the cell wall and soluble fractions, respectively, with Mg concentration decreasing by 15.4% in roots and 46.9% in leaves under Mg deficiency, while Ca concentration decreased by 27.6% in roots and increased by 23.6% in parent leaves. Approximately 90% of Mg exists in inorganic, water-soluble, and pectate and protein-bound forms, and nearly 90% of Ca exists in water-soluble, pectate and protein-bound, phosphate and oxalate acid forms. Except for the decreased inorganic Mg in roots and water-soluble Mg and Ca in leaves, Mg deficiency increased the proportions of Mg and Ca in all chemical forms. However, Mg deficiency generally increased the Ca/Mg ratio in various organs, subcellular and chemical forms, with negative relationships between Mg concentration and Ca/Mg ratio, and the variations of Mg and Ca were highly separated between Mg supply and organs. In conclusion, our results provide insights into the effects of Mg supply on Mg and Ca homeostasis in citrus plants.
镁（Mg）和钙（Ca）是植物中两种必需的大量营养素；然而，柑橘类植物中镁和钙在器官、亚细胞和化学形态方面的浓度特征及其相互关系，尤其是在不同镁供应条件下，尚未得到充分了解。在本研究中，将脐橙幼苗（品种：雪柑）种植在缺镁（0 mmol Mg/L）和镁充足（2 mmol Mg/L）条件下，以研究不同器官和组分中镁和钙稳态的响应。与镁充足相比，缺镁显著降低了根和地上部的生长，其中枝条器官的地上部生物量减少幅度大于母枝器官。除了增加母茎和侧根器官中的钙浓度外，缺镁还显著降低了柑橘幼苗中镁和钙的浓度及积累量，进一步改变了它们在不同器官中的分布。超过50%的钙和镁分别被隔离在细胞壁和可溶性组分中，缺镁条件下，根中镁浓度降低了15.4%，叶中降低了46.9%，而根中钙浓度降低了27.6%，母叶中增加了23.6%。约90%的镁以无机、水溶性、果胶酸盐结合和蛋白质结合形式存在，近9%的钙以水溶性、果胶酸盐结合和蛋白质结合、磷酸盐和草酸盐形式存在。除了根中无机镁减少以及叶中水溶性镁和钙减少外，缺镁增加了所有化学形态中镁和钙的比例。然而，缺镁通常会增加各器官、亚细胞和化学形态中的钙/镁比，镁浓度与钙/镁比呈负相关，且镁和钙的变化在镁供应和器官之间高度分离。总之，我们的结果为镁供应对柑橘类植物中镁和钙稳态的影响提供了见解。
