Rice (Oryza sativa L.) is among the most consumed cereals in the world. Its growth is severely affected by excessive salinity, leading to considerable negative economic impacts. Thus, BRS Esmeralda and São Francisco rice cultivars, presenting antagonist cultivation recommendations and differential salt tolerance, were selected to examine how salt stress influences ionic homeostasis and photosynthetic capacity. Phenotypic, physiological, molecular, and morphological results indicated that São Francisco had a better potential to withstand salt stress than BRS Esmeralda. Although salinity promoted a significant increase in Na⁺ content, particularly in BRS Esmeralda, the harmful effects were less severe in São Francisco. The upregulation of SOS and NHX gene expressions revealed that São Francisco used these mechanisms to control Na⁺ accumulation in cytosol. Besides, São Francisco plants were efficient in reducing the adverse effects of salinity on photosynthesis. Under salt stress, São Francisco leaves exhibited better effective quantum efficiency of PSII, photochemical extinction coefficient, and electron transport rate. Besides, the relative energy excess in PSII and non-photochemical quenching were both smaller compared to BRS Esmeralda. Na⁺ cytotoxic effects damaged the chloroplast ultrastructure in BRS Esmeralda, reducing photosynthetic capacity. In contrast, the São Francisco cultivar's better performance was followed by an efficient Na⁺ exclusion and photosynthetic capacity maintenance, leading to lower growth losses. Overall, the findings are suitable for understanding salt responses and developing functional markers associated with salt stress tolerance improvement in rice.

大米（Oryza sativa L.）是世界上消费量最大的谷物之一。它的生长受到过度盐分的严重影响，导致相当大的负面经济影响。因此，选择了 BRS 埃斯梅拉达和圣弗朗西斯科水稻品种，提出了拮抗剂栽培建议和不同的耐盐性，以研究盐胁迫如何影响离子稳态和光合能力。表型、生理、分子和形态学结果表明，圣弗朗西斯科比 BRS Esmeralda 具有更好的承受盐胁迫的潜力。尽管盐分促进了 Na ⁺含量的显着增加，特别是在 BRS 埃斯梅拉达，但在圣弗朗西斯科的有害影响不那么严重。SOS的上调和NHX 基因表达表明 São Francisco 使用这些机制来控制细胞质中Na ^{+ 的}积累。此外，圣弗朗西斯科植物在减少盐度对光合作用的不利影响方面是有效的。在盐胁迫下，圣弗朗西斯科叶片表现出更好的PSII有效量子效率、光化学消光系数和电子传输速率。此外，与 BRS Esmeralda 相比，PSII 和非光化学猝灭的相对能量过剩都较小。Na ⁺细胞毒性作用破坏了 BRS Esmeralda 中的叶绿体超微结构，降低了光合能力。相比之下，圣弗朗西斯科品种的更好表现紧随其后的是高效的 Na ⁺排除和光合能力维持，导致生长损失降低。总体而言，这些发现适用于了解盐分反应和开发与水稻耐盐性改善相关的功能标记。