Soil salinity is one of the adversity stresses plants face, and antioxidant defense mechanisms play an essential role in plant resistance. We investigated the effects of exogenous calcium on the antioxidant defense system in peanut seedling roots that are under salt stress by using indices including the transcriptome and absolute quantitative metabolome of flavonoids. Under salt stress conditions, the antioxidant defense capacity of enzymatic systems was weakened and the antioxidant capacity of the linked AsA-GSH cycle was effectively inhibited. In contrast, the ascorbate biosynthesis pathway and its upstream glycolysis metabolism pathway became active, which stimulated shikimate biosynthesis and the downstream phenylpropanoid metabolism pathway, resulting in an increased accumulation of flavonoids, which, as one of the antioxidants in the non-enzymatic system, provide hydroxyl radicals to scavenge the excess reactive oxygen species and maintain the plant’s vital activities. However, the addition of exogenous calcium caused changes in the antioxidant defense system in the peanut root system. The activity of antioxidant enzymes and the antioxidant capacity of the AsA-GSH cycle were enhanced. Therefore, glycolysis and phenylpropanoid metabolism do not exert antioxidant function, and flavonoids were no longer synthesized. In addition, antioxidant enzymes and the AsA-GSH cycle showed a trade-off relationship with sugars and flavonoids.

Saline–alkaline stress is a major factor limiting agricultural development, with calcium (Ca²⁺) playing a role in regulating plant tolerance through multiple signaling pathways. However, the specific mechanisms by which Ca²⁺ mediates saline–alkaline stress tolerance at the molecular level remain incompletely understood. This study investigates the effects of exogenous Ca²⁺ application on enhancing plant tolerance to saline–alkaline stress, focusing on its impact on the antioxidant system and Ca²⁺ and reactive oxygen species (ROS) signaling pathways. Through physiological assays and transcriptomic analyses, we evaluated oxidative damage markers, antioxidant enzyme activities, and the expression of key Ca²⁺ and ROS signaling genes. The results showed that saline–alkaline stress significantly elevated ROS levels, which led to increased membrane lipid peroxidation and induced upregulation of antioxidant response elements in castor roots. Exogenous calcium treatment reduced ROS accumulation by increasing superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activities and decreasing malondialdehyde (MDA) levels, demonstrating a marked improvement in the antioxidant system. Transcriptomic analysis identified CAT2 (LOC107261240) as the primary target gene associated with increased CAT activity in response to exogenous calcium. Additionally, the upregulation of specific Ca²⁺ channels, Ca²⁺ sensors, ROS receptors, and antioxidant-related genes with calcium treatment highlights the critical role of Ca²⁺–ROS signaling crosstalk in enhancing stress tolerance. Protein–protein interaction analysis identified APX3 and other hub genes involved in Ca²⁺–ROS signaling transduction and the regulation of antioxidant activity. These findings enhance our understanding of calcium’s complex regulatory roles in plant abiotic stress responses, offering new theoretical insights for improving crop resilience in agriculture.

Salt stress seriously hinders the normal growth of plant seedling roots. Magnesium, as one of the essential medium elements for plant growth, can effectively alleviate the damage of salt stress to plant roots, but the key genes involved and their mechanism are still unclear. The purpose of this study was to explore the related molecular mechanism of exogenous magnesium regulating cation homeostasis in peanut seedlings under salt stress. Firstly, according to plant physiology experiments, it was found that exogenous magnesium treatment significantly improved the tolerance of peanut seedlings to salt stress. After that, the transcriptome data were integrated, and further gene expression analysis showed that the expression of genes such as CNGC1, NCLs, and NHX7 was regulated under exogenous magnesium treatment, which effectively reduced the accumulation of sodium ions in cells. At the same time, exogenous magnesium also regulates the expression of genes such as ACAs and POTs and maintains the homeostasis of calcium and potassium ions in cells. These results reveal the molecular mechanism of exogenous magnesium regulating the cation homeostasis of peanut seedlings under salt stress, which provides an important reference for further revealing the key genes of salt tolerance in plants.

Alkaline stress (AS) is one of the major threats that severely affects rice growth and grain yield. However, the differences in the damage caused by the main components of soda saline-alkali land, sodium carbonate (Na₂CO₃), and sodium bicarbonate (NaHCO₃) to rice seedlings are still unclear. This study explored the effects of different carbonate stresses (Na₂CO₃ and NaHCO₃) on rice seedling growth, root damage, physiological responses, and molecular changes. By administering equivalent concentrations of sodium ions through these different carbonate treatments, we observed that both stresses significantly inhibited rice growth. However, the inhibitory effect was more pronounced under the Na₂CO₃ treatment. Compared with the NaHCO₃ treatment, Na₂CO₃ stress caused more severe damage to root cell membranes and led to a substantial decline in root vigor. Moreover, the contents of reactive oxygen species (ROS) and malondialdehyde (MDA) were markedly increased, indicating that Na₂CO₃ induces more severe oxidative damage. Transcriptomic and metabolomic analyses revealed a greater number of differentially expressed genes (DEGs) and differentially expressed metabolites (DEMs) in the Na₂CO₃ treatment group. The integrative analysis and validation demonstrated that pathways related to auxin, ascorbate, flavonoids, and glutathione metabolism were particularly enriched under Na₂CO₃ stress. These findings suggest that Na₂CO₃ stress may interfere with auxin signaling pathways and exerts a more profound impact on endogenous antioxidant systems, affecting rice growth at multiple levels. In summary, this research highlights the differential impacts of Na₂CO₃ and Na₂CO₃ stresses on rice seedling growth, physiology, and molecular processes, particularly oxidative damage and antioxidant responses. The insights gained provide a valuable theoretical foundation for enhancing rice alkali tolerance and developing strategies for the rational cultivation of rice in saline-alkaline soils.