The Ionic and Metabolic Response Mechanisms of Kochia scoparia in Response to Saline–Alkaline Stress

Saline-alkaline stress is a critical environmental issue that limits plant growth and crop production. With the expansion of salinized land, investigating the response mechanisms of plants to salt-alkali stress is crucial. Integrated ionomic and metabolomic analyses were employed to investigate the response mechanisms of <i>Kochia scoparia</i> in our studies. Compared with the halophyte <i>Suaeda salsa</i>, <i>K. scoparia</i> exhibits distinct ionic and metabolic strategies for coping with saline-alkaline stress. Ca, Mg, and B were significantly accumulated in <i>K. scoparia</i> to alleviate ion toxicity and oxidative damage and to maintain cellular stability at the ionic element level. Sugars, alcohols, esters, and phenolic compounds were found to play key roles in resisting saline-alkaline stress at the metabolic level. Among these, sugars, alcohols, and esters were mainly involved in mitigating salt stress. Targeted metabolomic analysis indicated that certain phenolic compounds-namely C6C1-compounds (p-hydroxybenzoic, gallic, vanillic, salicylic, and syringic acids), C6C3 (caffeic acid, p-coumaric, p-hydroxycinnamic, cinnamic, and ferulic acids), and C6C3C6 (naringenin, quercetin, genistein, petunidin, and luteolin)-were significantly accumulated in <i>K. scoparia</i>. These compounds help mitigate saline-alkaline stress by enhancing reactive oxygen species (ROS) scavenging, modulating signaling pathways, reprogramming the osmoprotectant metabolism, and remodeling cell wall defense. This study elucidates the advantages and mechanistic of <i>K. scoparia</i>'s tolerance to saline-alkaline stress, providing a theoretical foundation for the repair and utilization of saline-alkaline soils.