Graphene oxide (GO), as a novel carbon-based nanomaterial (CBN), has been widely applied to every respect of social life due to its unique composite properties. The widespread use of GO inevitably promotes its interaction with heavy metal cadmium (Cd), and influences its functional behavior. However, little information is available on the effects of GO on greening hyperaccumulators under co-occurring Cd. In this study, we chose a typical greening hyperaccumulator (Lonicera japonica Thunb.) to show the effect of GO on Cd accumulation, growth, net photosynthesis rate (P_n), carbon sequestration and oxygen release functions of the plant under Cd stress. The different GO-Cd treatments were set up by (0, 10, 50 and 100 mg L⁻¹) GO and (0, 5 and 25 mg L⁻¹) Cd in solution culture. The maximum rate of Cd accumulation in the roots and shoots of the plant were increased by 10 mg L⁻¹ GO (exposed to 5 mg L⁻¹ Cd), indicating that low-concentration GO (10 mg L⁻¹) combined with low-concentration Cd (5 mg L⁻¹) might stimulate the absorption of Cd by L. japonica. Under GO treatments without Cd, the dry weight of root and shoot biomass, P_n value, carbon sequestration per unit leaf area and oxygen release per unit leaf area all increased in various degrees, especially under 10 mg L⁻¹ GO, were 20.67%, 12.04%, 35% and 28.73% higher than the control. Under GO-Cd treatments, it is observed that the cooperation of low-concentration GO (10 mg L⁻¹) and low-concentration Cd (5 mg L⁻¹) could significantly stimulate Cd accumulation, growth, photosynthesis, carbon sequestration and oxygen release functions of the plant. These results indicated that suitable concentrations of GO could significantly alleviate the effects of Cd on L. japonica, which is helpful for expanding the phytoremediation application of greening hyperaccumulators faced with coexistence with environment of nanomaterials and heavy metals.

In recent years, there has been a significant growth in scholarly attention to the effects of Cd stress on horticultural plants, as reflected by the abundance of research articles on this issue in academic publications. Therefore, it is necessary to conduct a review of current research and provide a comprehensive perspective to quickly grasp the latest developments and future trends in the research field of “horticultural plants-Cd responses”. By utilizing a visualizing bibliometric analysis software CiteSpace, this study integrated and analyzed a total of 4318 relevant research records—2311 from the Web of Science (WOS) database and 2007 from the China National Knowledge Infrastructure (CNKI) database—related to “horticultural plants-Cd responses”, covering the period from 1999 to 2024. A visual analysis was conducted in the form of knowledge mappings, including the current research status of “horticultural plants-Cd responses”, as well as the differences in publications’ temporal distribution, spatial distribution (cooperation networks) and intellectual base between China and foreign countries, precisely uncovering the core aspects of research topics related to the field. The results indicated the following: (1) Scientific research on “horticultural plants-Cd responses” has experienced a significant increase in publication volume and has entered a phase of rapid development. Globally, there has been an annual average increase of 217 articles in the WOS since 2019, while in China, the annual average increase has been 134 articles in the CNKI since 2015. (2) China is the most productive country in terms of publication volume (1165 articles, 52.79%), engaging in active partnerships with other countries worldwide. Chinese scholars (Lin L. and Liao M.) are leading researchers in both domestic and international research fields of “horticultural plants-Cd responses”. The network of collaborations among authors and institutions in the WOS database seemed denser compared to that in the CNKI database. (3) International research hotspots have focused on accumulation, tolerance and oxidative stress, while domestically, the focus has been on antioxidant enzymes, growth and seed germination. Phytoremediation, subcellular distribution and the transcriptome are the world’s emerging topics, while in China, growth and physiological characteristics are still emerging topics. (4) In comparison, China exhibited a lagging development trend, which is reflected in the fact that it began to focus on gene expression and transcriptome research only after the global frontier shifted towards biochar and cadmium co-stress and yield response. Based on these, this study provides a systematic theoretical basis for subsequent research on “horticultural plants-Cd responses”, aiding scholars in their efforts to understand the dynamic frontiers and address the challenges in this field.

Increases in near-surface ozone (O₃) concentrations is a global environmental problem. High-concentration O₃ induces stress in plants, which can lead to visible damage to plants, reduced photosynthesis, accelerated aging, inhibited growth, and can even plant death. However, its impact has not been comprehensively evaluated because of the response differences between individual plant species, environmental O₃ concentration, and duration of O₃ stress in plants. We used a meta-analysis approach based on 31 studies 343 observations) to examine the effects of elevated O₃ on malondialdehyde (MDA), superoxide dismutase (SOD), and peroxidase (POD) activities in herbaceous plants. Globally, important as they constitute the majority of the world’s food crops. We partitioned the variation in effect size found in the meta-analysis according to the presence of plant species (ornamental herb, rice, and wheat), O₃ concentration, and duration of O₃ stress in plants. Our results showed that the effects of elevated O₃ on plant membrane lipid peroxidation depending on plant species, O₃ concentration, and duration of O₃ stress in plants. The wheat SOD and POD activity was significantly lower compared to the herbs and rice (P<0.01). The SOD activity of all herbaceous plants increased by 34.6%, 10.5%, and 26.3% for exposure times to elevated O₃ environments of 1–12, 13–30, and 31–60 days, respectively. When the exposure time was more than 60 days, SOD activity did not increase but significantly decreased by 12.1%. However, the POD activity of herbaceous plants increased by 30.4%, 57.3%, 21.9% and 5.81%, respectively, when exposure time of herbaceous plants in elevated O₃ environment was 1–12, 13–30, 31–60 and more than 60 days. Our meta-analysis revealed that (1) rice is more resistant to elevated O₃ than wheat and ornamental herbs likely because of the higher activity of antioxidant components (e.g., POD) in the symplasts, (2) exposure to elevated O₃ concentrations for >60 days, may result in antioxidant SOD lose its regulatory ability, and the antioxidant component POD in the symplast is mainly used to resist O₃ damage, and (3) the important factors affected the activity of SOD and POD in plants were not consistent: the duration of O₃ stress in plants was more important than plant species and O₃ concentration for SOD activity. However, for POD activity, plant species was the most important factor.

Unreasonable nitrogen (N) management and the shortage of groundwater resources are prominent problems faced by intensive farmland in North China. The main processes to reduce N₂O emissions under drip irrigation still need to be further explored. This study conducted a three-year field experiment (2021–2024) of wheat–maize cropping system in Hebei Province to study the effects of four N levels under drip irrigation (i.e., N0: no N applied; N150: 150 kg N ha⁻¹; N210: 210 kg N ha⁻¹; N270: 270 kg N ha⁻¹) on yield, N₂O emission, soil carbon (C) and N fractions, enzymes, and N functional genes. The results showed that N rate significantly affected N₂O emissions (p < 0.05). The highest value of N₂O emissions (10.64 kg N ha⁻¹) over three years and yield-scale N₂O emissions (0.25 g kg⁻¹) were found under N270, which were 32.1% and 78.6% higher than those of N210. No significant difference in annual yields between N210 and N270 was found, but the annual yield of N150 was decreased by 14.4% as compared to N210. N rate significantly affected soil C-N fractions and enzymes, in which NO₃⁻-N, MBC, DON, amoA-AOB, and UE enzymes, as the major factors of soil properties, N functional genes, and enzymes affecting N₂O emissions, were more favorably regulated along with the increase in fertilizer N rate. Correlation analysis indicated that amoA-AOB was significantly correlated to N fractions (i.e., NH₄⁺-N, NO₃⁻-N, TN, DON and MBN) and UE enzymes. Structural equation modeling further proved that an increase in fertilizer N rate directly increased enzyme activities related to N transformation, which increased N fractions, thus promoting the abundance of amoA-AOB genes involved in nitrification that stimulate N₂O emissions. Therefore, these findings underscore that N210 was an optimal fertigation strategy for minimizing N₂O emissions without compromising yield, offering a practical pathway for sustainable intensification in water-limited regions.