Primary mechanism through which nanomaterials enhance plant photosynthesis.

Soybean, an important cash crop, is often affected by soil salinity, which is one of the important types of abiotic stress that affects its growth. Poly (acrylic) acid coated Mn₃O₄ (PMO) has been reported to play a vital role in defending against a variety of abiotic stresses in plants. To date, the effects of PMOs on soybean have not been reported; this study explored the mechanism of PMO-enhanced soybean germination under salt stress. In this experiment, 100 mg/L PMO was used as an immersion agent with a salt treatment of 150 mM NaCl. The results showed that when compared with the PMO treatment, salt stress significantly decreased the germination rate, fresh weight, carbohydrate content, and antioxidant enzyme activity of soybean and significantly increased the contents of reactive oxygen species, malondialdehyde, and osmoregulatory substances. However, PMO treatment enhanced the antioxidant defense system and significantly reduced the malondialdehyde content of soybean. Moreover, the activities of H⁺-ATPase and Ca²⁺-ATPase were significantly higher in treated soybean than in the control, and the content of ATP was also higher in treated soybean than in the control. Generally, PMO regulates the homeostasis of reactive oxygen species and reduces ATP consumption, thereby improving the ability of soybeans to germinate under salt stress. This study provides new insights into how nanomaterials improve plant salt tolerance.

Cadmium (Cd) pollution seriously threatens food safety. Plant-derived nanomaterials, due to their environmental friendliness, have emerged as a promising approach for crop stress tolerance regulation; however, their mechanisms under Cd stress remain unclear. In this study, licorice–wolfberry-derived nanocomposites (LW-CNs) were synthesized via a one-step hydrothermal reaction following an established protocol, and their physicochemical properties have been characterized in our previous studies. These were foliarly applied at 200 mg/L to soybean seedlings under 300 μmol/L Cd stress, and the physiological mechanisms underlying their alleviation of Cd toxicity were systematically analyzed. The results showed that Cd stress significantly inhibited soybean seedling growth, reducing net photosynthetic rate from 6.42 to 0.29 μmol·m⁻²·s⁻¹, and induced substantial accumulation of H₂O₂, O₂·⁻, and MDA in leaves. After LW-CN application, plant height, shoot fresh weight, and root fresh weight increased by 5.8%, 29.0%, and 28.2%, respectively, while Pn recovered to 0.94 μmol·m⁻²·s⁻¹. Mechanistic analysis revealed that the ameliorative effects of LW-CNs resulted from four synergistic actions: (i) maintaining chloroplast ultrastructural integrity, with Pn recovery accompanied by stable intercellular CO₂ concentration, suggesting that the relief of photosynthetic limitation was unlikely to be attributable to stomatal factors alone; (ii) systemically upregulating SOD, POD, CAT, APX, DHAR, and GR activities, modulating the redox status of the AsA-GSH cycle, and significantly reducing H₂O₂ (2.77 to 2.14 μmol/g), O₂·⁻ (284.73 to 247.40 nmol/g), and MDA (79.29 to 58.40 nmol/g) contents, thereby maintaining ROS homeostasis; (iii) decreasing Cd concentrations in roots, stems, and leaves, and reducing chloroplast Cd co-localization signals (0.774 to 0.171), thus mitigating direct damage to photosynthetic machinery at the source; and (iv) organ-specifically reconfiguring nitrogen metabolism, enhancing NR, GOGAT, and GDH activities and glutamate accumulation in roots, and promoting nitrogen redistribution among roots, stems, and leaves. These findings provide a multidimensional physiological framework—covering Cd-accumulation reduction, photosynthesis protection, redox stabilization, and nitrogen redistribution—for understanding how a plant-derived nanomaterial enhances soybean Cd tolerance, and offer a reference for developing plant-based strategies to sustain soybean production in Cd-contaminated farmlands.

Salinity is a major factor limiting the increase in crop yield around the world. Wheat starch and straw are important raw materials for producing bioethanol, and their productivity is adversely affected by salinity. Polyacrylic acid-modified Mn₃O₄ nanoparticles (PMO) have been reported to improve crop tolerance to stressors, including salt stress. Therefore, this study aimed to elucidate the mechanism by which seed soaking with PMOs enhances wheat salt tolerance. PMO seed soaking promoted wheat germination (increase of 30.9%) under salt stress, and seedlings treated with PMO seed soaking had a higher fresh weight (increase of 31.4%). PMO seed soaking increased the POD activity (by 31.9%) but decreased superoxide dismutase and catalase activities of wheat seeds and the O₂⁻ and H₂O₂ contents (by 25.0 and 71.4%, respectively). Furthermore, PMO soaking increased the ATP, NADPH, and NADH contents (by 367.6, 212.0, and 283.2%, respectively) by regulating sugar metabolism and enhanced the ascorbic acid–glutathione cycle. Additionally, the PMO soaking treatment optimized energy allocation in wheat under salt stress and increased yield (by 9.7%). PMO modulated sugar metabolism, thereby optimizing energy allocation to plant growth and the antioxidant system, which enhanced wheat germination and yield formation under salt stress.