Meteorological factors are the key drivers of air pollution. Stable weather conditions, the boundary layer height, and temperature inversion significantly influence the dispersion of particulate matter, which is also associated with the aerodynamic properties of particles. However, limited studies have been conducted on this topic in northeast China. This study investigates the influence of meteorological factors on PM_2.5 pollution under cold weather conditions, employing both qualitative and quantitative methods. The key meteorological factors considered include temperature difference, relative humidity, wind speed and direction, the boundary layer height (BLH), and temperature inversion. The stable weather index (SWI) is introduced as a quantitative measure of the stability of weather based on data from the last five winters in a typical megacity of northeast China. The monthly PM_2.5 concentrations recorded during the last five Februarys ranged from 59.79 μg/m³ to 85.68 μg/m³, with the highest daily concentration reaching 417 μg/m³. A new parameter, ‘temperature difference (ΔT)’, is defined in this study as the difference in temperature between two consecutive days, calculated by subtracting the previous day’s temperature from the current day’s. The temperature differences were found to have a significantly positive correlation with the differences in PM_2.5 concentrations (p < 0.01). The results showed that PM_2.5 pollution was associated with increased temperature, higher relative humidity, and lower wind speed, or any combination of these factors. The SWI explained 65% and 64% of the variances in air quality index (AQI) and PM_2.5 pollution, respectively. When the predicted SWI exceeds 10, the likelihood of particle pollution increases. A lower BLH, in conjunction with a thicker inversion layer, contributes to the formation of severe particle pollution. In the early stages of a winter pollution episode in Harbin, the temperature inversion layer thickened and intensified, with the inversion top height reaching approximately 200 m. The boundary layer remained below 200 m, resulting in a poor vertical dispersion condition. PM_2.5 pollution, therefore, is influenced by the combined effects of multiple meteorological factors. Our study quantitatively analyzed the characteristics of weather conditions and their impacts on air quality, which could provide scientific evidence for air pollution prediction and assist in making specific policy interventions, particularly for the upcoming ninth Asian Winter Games in Harbin in February 2025.

Background Drought is a critical limiting factor affecting the growth and development of spring maize (Zea mays L.) seedlings in northeastern China. Sodium 5-nitroguaiacol (5-NGS) has been found to enhance plant cell metabolism and promote seedling growth, which may increase drought tolerance. Methods In the present study, we investigated the response of maize seedlings to foliar application of a 5-NGS solution under osmotic stress induced by polyethylene glycol (PEG-6000). Four treatment groups were established: foliar application of distilled water (CK), foliar application of 5-NGS (NS), osmotic stress + foliar application of distilled water (D), and osmotic stress + foliar application of 5-NGS (DN). Plant characteristics including growth and photosynthetic and antioxidant capacities under the four treatments were evaluated. Results The results showed that under osmotic stress, the growth of maize seedlings was inhibited, and both the photosynthetic and antioxidant capacities were weakened. Additionally, there were significant increases in the proline and soluble sugar contents and a decrease in seedling relative water content (RWC). However, applying 5-NGS alleviated the impact of osmotic stress on maize seedling growth parameters, particularly the belowground biomass, with a dry mass change of less than 5% and increased relative water content (RWC). Moreover, treatment with 5-NGS mitigated the inhibition of photosynthesis caused by osmotic stress by restoring the net photosynthetic rate (Pn) through an increase in chlorophyll content, photosynthetic electron transport, and intercellular CO2 concentration (Ci). Furthermore, the activity of antioxidant enzymes in the aboveground parts recovered, resulting in an approximately 25% decrease in both malondialdehyde (MDA) and H2O2. Remarkably, the activity of enzymes in the underground parts exhibited more significant changes, with the contents of MDA and H2O2 decreasing by more than 50%. Finally, 5-NGS stimulated the dual roles of soluble sugars as osmoprotectants and energy sources for metabolism under osmotic stress, and the proline content increased by more than 30%. We found that 5-NGS played a role in the accumulation of photosynthates and the effective distribution of resources in maize seedlings. Conclusions Based on these results, we determined that foliar application of 5-NGS may improve osmotic stress tolerance in maize seedlings. This study serves as a valuable reference for increasing maize yield under drought conditions.

Blue honeysuckle is an emerging small berry with high nutritional value; However, the soft texture of its fresh fruit leads to poor storability and transportability, severely limiting its economic returns. Calcium is a key element in maintaining the structural integrity of plant cell walls and membranes, and plays a decisive role in fruit firmness and postharvest quality. To elucidate the effects of different calcium fertilizers on the fruit firmness, yield, and fruit quality of blue honeysuckle, a two-year field experiment was conducted using foliar application of 2 L of calcium fertilizer (CaC, CaA, CaL, SAC and AAC) at a concentration of 1 mg/L, with the control receiving an equal volume of water. The results showed that sugar alcohol calcium had the best effect on fruit firmness, fresh weight, yield, solid-acid ratio, total anthocyanins, and ascorbic acid, significantly improving yield and quality. Amino acid calcium was most effective in increasing fruit volume and fruit number per plant. Calcium acetate and calcium lactate showed balanced improvements across indicators. Calcium chloride significantly enhanced fruit shape index, total phenols, and total flavonoids. These findings elucidate the specific effects of various treatments on key fruit traits, providing a theoretical basis for precision cultivation and quality regulation, thereby facilitating the standardization and high-quality development of the industry.

Soil salinity is one of the most limiting factors for global agriculture, threatening crop productivity and food security. This chapter synthesizes current knowledge on the physiological and ecological mechanisms underlying plant adaptation to salt stress and proposes integrative biological strategies to enhance crop salt tolerance. Particular emphasis is placed on root interactions and rhizosphere processes, beneficial microbial inoculants, and the use of biostimulants and exogenous signaling compounds. By evaluating these strategies collectively, the chapter highlights their synergistic potential to provide sustainable and ecosystem-based solutions for salinity management. The chapter begins with root-mediated mechanisms that regulate ion transport, water balance, and rhizosphere modifications. It then addresses the role of beneficial microorganisms in promoting plant salt resilience through nutrient mobilization, hormone regulation, and stress alleviation. The potential of biostimulants and small molecules as external modulators of stress responses is also explored. Finally, this chapter integrates these approaches into a holistic framework, emphasizing the importance of ecological synergy and cross-disciplinary collaboration in developing scalable solutions. By bridging insights from plant physiology, soil microbiology, and agricultural practices, and incorporating the application of big data and large-scale models for optimizing salt tolerance alongside precision management in smart agriculture, this chapter provides a roadmap for advancing green and integrative strategies to enhance crop adaptation and performance in saline environments.

Blue honeysuckle (Lonicera caerulea L.) is subject to environmental stressors, leading to variability in both severe fruit drop during development and fruit quality. Zinc, an essential micronutrient, is critical to sustainable fruit tree production by enhancing yield and nutritional quality. Different forms of zinc fertilizers, particularly nano-zinc versus conventional ionic zinc, exhibit marked differences in absorption efficiency and agronomic performance, thereby determining their practical efficacy. In this two-year study, we evaluated the effects of foliar-applied zinc forms, ZnO nanoparticles (30, 50, and 90 nm) and ionic zinc (ZnCl₂ and ZnSO₄), applied at the young fruit, veraison, and maturity stages on yield and fruit quality. Results showed that ZnO nanoparticles were more effective than ionic zinc at 80 mg/L. In particular, among the ZnO NP treatments, 90 nm ZnO NPs exhibited the best overall effect, significantly improving fruit quality. The 30 nm ZnO NPs treatment performed best in terms of single fruit weight, yield per plant, and fruit firmness. This study highlights the potential of nano-zinc to enhance productivity and quality in blue honeysuckle, providing a theoretical basis for selecting optimal zinc fertilizer types and particle sizes in specialty berry production, with implications for sustainable, high-quality fruit cultivation.

Bolboschoenus planiculmis is a dominant clonal sedge in saline–alkaline wetlands of the Songnen Plain, and its corms provide important food resources for migratory waterbirds. However, its growth mechanism under saline alkali conditions is still unclear. We combined a field survey with a greenhouse experiment that decoupled saline–alkaline stress into two associated constraints, physiological drought and nitrogen deficiency. Six treatments were established: control, nitrogen deficiency, PEG-induced physiological drought, their combination, moderate saline–alkaline stress, and severe saline–alkaline stress. In the field, soil electrical conductivity and pH increased synchronously, whereas inorganic nitrogen availability was heterogeneous. In the greenhouse, compared with the CK, moderate and severe saline–alkaline stress reduced total biomass by approximately 47% and 51%, respectively, and inhibited leaf growth, root expansion, and corm biomass. It also increased SOD and CAT activities, and ${\mathrm{H}}_2$${\mathrm{O}}_2$ and MDA accumulated. ¹⁵N tracing further showed reduced nitrogen enrichment and lower nitrogen input into corms under saline–alkaline stress, despite partial maintenance of corm allocation. Integrated trait analyses suggested that growth limitation was associated with oxidative damage, restricted morphological development, defense costs, and reduced nitrogen acquisition. These findings provide a plant-level perspective that may inform future assessments of belowground food-resource conditions in migratory waterbird stopover habitats.