Physiological and Molecular Mechanisms of Saline–Alkali Stress Affecting Rice Growth and Regulation of Stress-Resistant Cultivation

Arable land is diminishing rapidly as a result of environmental degradation and urbanization. The development and utilization of saline–alkali soils therefore represent an important strategy for ensuring global food security. Rice (Oryza sativa L.) is a staple food for over half of the global population, yet its productivity is severely constrained by saline–alkali stress. Salinity (mainly NaCl) and alkalinity (high pH caused by Na2CO3/NaHCO3) markedly impair both yield formation and grain quality. This review establishes diagnostic thresholds for salinity (ECe) and alkalinity (pH) to mitigate their adverse effects. The effects of saline–alkali stress on rice germination, seedling establishment, plant growth, reproductive development, and grain filling are summarized. And the underlying physiological and molecular mechanisms are elucidated, including ion homeostasis (mediated by OsHKT1;5, OsSOS1, and OsNHX1), osmotic adjustment, as well as alkalinity-specific processes such as rhizosphere acidification, organic acid exudation, and Fe/Zn acquisition under high pH, endogenous hormone crosstalk, antioxidant defense, starch/protein biosynthesis, and related key genes and quantitative trait loci (QTLs). Furthermore, recent advances of stress-resistant cultivation and regulation strategies are highlighted. On this basis, future research directions are prospected. This review provides a comprehensive understanding of the physiological and molecular mechanisms underlying rice saline–alkali tolerance, with important implications for achieving high yield and quality in rice production on saline–alkali soil.