Plants

Iron deficiency limits plant growth and is usually addressed with iron fertilizers. Iron−based nanomaterials (nZVI, α−FeOOH, α−Fe₂O₃, γ−Fe₂O₃, and Fe₃O₄) show promise as novel alternatives, but the effects of sulfide nano−zero−valent iron (S−nZVI) on crops remain little studied. Thus, this study aimed to synthesize a novel iron−based nanomaterial, S−nZVI, using a one−step method, and to evaluate the effects of S−nZVI and nZVI at concentrations ranging from 5 to 100 mg L⁻¹ on the physiological and photosynthetic characteristics of Chinese cabbage (Brassica rapa L.). In the study, foliar application of iron nanoparticles increased leaf area, biomass, and photosynthesis, with 50 mg L⁻¹ the most efficient concentration (S−nZVI > nZVI). Moreover, the photosynthetic rate of the leaves increased significantly (>200%), and carbohydrate accumulation also increased significantly. Additionally, S−nZVI treatment increased leaf iron content by 5.8−fold compared to the control group, likely by enhancing the activity of antioxidant enzymes. However, the 100 mg L⁻¹ S−nZVI treatment significantly inhibited these physiological and biochemical indicators. Overall, the foliar S−nZVI (50 mg L⁻¹) enhanced Chinese cabbage growth by alleviating iron deficiency, boosting antioxidant activity, and reducing oxidative stress; further field trials are needed to verify its effectiveness and cost−efficiency.

The expansion of native invasive plants severely impacts alpine meadow ecosystems and regional development on the Qinghai-Xizang Plateau by reducing vegetation productivity and hindering livestock production. However, the rules underlying their effects on forage grass establishment and effective mitigation strategies remain poorly understood. Here, using three main allelochemicals—benzoic acid (BA), caffeic acid (CA), and p-hydroxybenzoic acid (HA)—from typical native invasive plants, we investigated concentration-dependent effects (0, 100, 300, and 500 mg/L) on the seed germination and seedling growth of four common forage species: Festuca elata Keng ex E. B. Alexeev (FE), Lolium perenne L. (LP), Medicago sativa L. (MS), and Trifolium repens L. (TR). Our findings revealed a concentration-dependent hormesis effect: low concentrations stimulated germination and growth, while inhibition intensified with increasing concentrations. Roots exhibited significantly higher sensitivity than stems (p < 0.01). The phytotoxic intensity of allelochemicals on forage grass growth follows the order BA > CA > HA. For germination (germination rate/potential), sensitivity orders were FE > LP > TR > MS and LP > FE > TR > MS, respectively. For seedling growth, toxicity orders were TR > MS > FE > LP (root length), TR > FE > MS > LP (root weight), TR > MS > FE > LP (stem length), and TR > FE > LP > MS (stem weight). In summary, different allelochemicals exerted significantly varied effects on the germination and growth of distinct forage grass species. Therefore, forage species selection should consider local allelochemical profiles, or alternatively, grass-legume mixtures could be employed to enhance biomass yield. Our findings provide valuable insights for developing effective grassland restoration strategies.

Practices that mitigate the deleterious effects of water deficit are of great importance for agricultural production in the semi-arid region of Northeastern Brazil. The objective of this study was to evaluate the effect of foliar application of salicylic acid on mitigating water deficit in the morphophysiology and yield components of sour passion fruit during different phenological stages. Treatments were arranged in a randomized block design in a 6 × 2 factorial scheme, consisting of six irrigation strategies under water deficit, based on reference evapotranspiration (ETr) [irrigation with 100% ETr throughout the entire cultivation cycle—IS1; irrigation with 50% ETr during the vegetative stage—IS2; flowering—IS3; fruiting—IS4; vegetative/flowering—IS5; and vegetative/fruiting—IS6], combined with or without salicylic acid (SA) application (0 and 1 mM). The application of 1.0 mM salicylic acid alleviated the effects of water deficit during the flowering stage, improving gas exchange, photochemical efficiency, relative water content, growth, and yield of sour passion fruit. In addition, it contributed to reducing electrolyte leakage in the leaf blade. Therefore, foliar application of salicylic acid represents a promising strategy to maintain the integrity of the photosynthetic apparatus and the productive performance of sour passion fruit under water deficit conditions.