Ke Zhang

Soil salinization severely constrains agricultural productivity and ecosystem sustainability. Suaeda salsa L. is a representative halophyte and demonstrates strong adaptability and potential for saline–alkali land restoration. To elucidate its physiological responses to salt stress, pot experiments were conducted under four salinity levels, namely CK (0 mM NaCl), LS (800 mM NaCl), MS (1600 mM NaCl), and HS (2400 mM NaCl), with 20 replicates per treatment, and the dynamics of endogenous hormone were analyzed using targeted metabolomics. The soil salinity levels were prepared by adding NaCl solutions of different molarities to achieve the desired salinity treatments. Results showed that low to moderate salinity (CK-LS: 0–800 mM) promoted growth performance, whereas higher salinity (HS: 2400 mM) significantly inhibited biomass accumulation, plant height, and stem diameter (p < 0.01). Salinity markedly affected nutrient accumulation in Suaeda salsa, with Na increasing up to 222%, K decreasing by 17–33%, Ca by 7–21%, Mg by 35–46%, and S by 45–56% across growth stages, while Fe remained unchanged. Under increasing salinity, stress-related hormones such as abscisic acid, jasmonic acid, salicylic acid, and indole derivatives were upregulated, while gibberellins decreased markedly. Zeatin and its derivatives showed significant increases under MS (p < 0.01). Correlation analysis indicated positive associations of abscisic acid and zeatin with growth traits, and negative correlations for gibberellins (R > 0.6). These findings suggest that Suaeda salsa adapts to saline conditions by modulating hormone-mediated ion balance, osmotic regulation, and defense metabolism, thereby optimizing growth and biomass allocation under salt stress.

With the increasing shortage of water resources, the current management of saline–alkali lands in semi-arid and arid areas has gradually transformed from “flooding irrigation with drainage” in the past to the combination of controlling regional water and salt balance, phytoremediation, and comprehensive utilization of halophyte resources. However, soil salinization caused by natural and anthropogenic factors has still been a major global environmental problem, which changes the chemical and physical properties of soil, deteriorates the quality of underground water, and decreases biodiversity, contributing to the loss of soil productivity and the succession of the halotolerant species. Euhalophytes, as the materials for phytoremediation, have been confirmed to be effective species in improving saline–alkali soils. They can redistribute salts in soil profile through the interaction of their desalinization potential and irrigation water leaching, thereby preventing secondary salinization and improving soil productivity for long-term reclamation of saline soil. In this review, the adaptation mechanisms of euhalophytes to saline soils are generalized from the views of morphological, physiological, and molecular aspects and evaluated for their potential to remediate saline soil through salt removal and promoting leaching. Euhalophytes can not only sequestrate salts inside the central vacuole of cells to tolerate higher salt stress by means of organ succulence, ion compartmentalization, and osmotic adjustment but facilitate water infiltration and salts leaching through root–soil interaction. The root system’s mechanical penetration increases soil porosity, decreases soil density, as well as stabilizes soil aggregates. Moreover, the suitability of phytoremediation in arid situations with low precipitation and non-irrigation and some agricultural practices need to be taken into account to avoid salts returning to the soil as forms of litter and deep tillage altering salt distribution. Hence, euhalophytes planting in semi-arid and arid areas should be evaluated from their adaptation, desalinization, and prospective commercial values, such as foods, biofuels, and medical development to alleviate soil secondary salinization crisis and enhance the productivity of arable agricultural land.

Halophytes possess the capacity to uptake high levels of salt through physiological processes and their root architecture. Here, we investigated whether halophyte/non-halophyte intercropping in saline soil benefits plant growth and contains root-dialogue between interspecific species. Field and pot experiments were conducted to determine the plant biomasses and salt and nutrient distributions in three suaeda (Suaeda salsa)/maize (Zea mays L.) intercropping systems, set up by non-barrier, nylon-barrier, and plastic-barrier between plant roots. The suaeda/maize intercropping obviously transferred more Na⁺ to the suaeda root zone and decreased salt and Na⁺ contents. However, the biomass of the non-barrier-treated maize was significantly lower than that of the nylon and plastic barrier-treated maize. There was lower available N content in the soil of the non-barrier treated groups compared with the plastic barrier-treated groups. In addition, the pH was lower, and the available nutrient content was higher in the nylon barrier, which suggested that rhizospheric processes might occur between the two species. Therefore, we concluded that the suaeda/maize intercropping would be beneficial to the salt removal, but it caused an adverse effect for maize growth due to interspecific competition, and also revealed potential rhizospheric effects through the role of roots. This study provides an effective way for the improvement of saline land.