As a globally critical pollutant, microplastics (MPs) have steadily increased in environmental concentrations owing to ongoing plastic production and agricultural practices, significantly affecting plant growth and greenhouse gas emissions. Arbuscular mycorrhizal fungi (AMF), which form symbiotic associations with approximately 80% of terrestrial plant species, generally enhance plant growth and mitigate soil emissions of nitrous oxide (N 2O) and methane (CH 4). However, the interactive effects of MPs and AMF on plant growth and greenhouse gas emissions remain poorly understood. Therefore, a pot experiment was conducted to examine the impacts of MPs and AMF on plant growth and soil greenhouse gas emissions. The results demonstrated that MPs significantly reduced soybean aboveground biomass, root biomass, yield, and root length ( P < 0.001), but increased nodule number. In contrast, AMF significantly increased soybean aboveground biomass, root biomass, yield, and root length ( P < 0.001), but decreased nodule number. Significant interactive effects between MPs and AMF were observed on soybean aboveground biomass, root biomass, yield, and root length ( P < 0.05). MPs significantly increased cumulative N 2O emissions from soil by 32.4% ( P < 0.001), but significantly decreased cumulative CH 4 emissions by 15% ( P < 0.01). AMF significantly reduced cumulative N 2O emissions by 23.7% ( P < 0.01) and slightly increased cumulative CH 4 emissions by 9.2% ( P > 0.05). However, no significant interaction between MPs and AMF was detected for either cumulative N 2O or CH 4 emissions ( P > 0.05). Our findings indicate that AMF can alleviate the inhibitory effects of MPs on soybean growth and reduce soil greenhouse gas emissions.

Previous studies have demonstrated changes in plant growth and reproduction in response to nutrient availability, but how investigations of such responses to multiple levels of nutrient enrichment remains unclear. In this study, we manipulated nitrogen (N) and phosphorus (P) availability to examine seed production responses to three levels each of N and P addition in a factorial experiment: no N addition (0 g N m-2 yr-1), low N addition (10 g N m-2 yr-1), high N addition (40 g N m-2 yr-1), and no P addition (0 g P m-2 yr-1), low P addition (5 g P m-2 yr-1), high P addition (10 g P m-2 yr-1). Low N addition enhanced seed production by 814%, 1371%, and 1321% under ambient, low, and high P addition levels, respectively. High N addition increased seed production by 2136%, 3560%, and 3550% under ambient, low, and high P addition levels, respectively. However, P addition did not affect seed production in the absence of N addition, but it did enhance it under N addition. Furthermore, N addition enhanced seed production mainly by increasing the tiller number and inflorescence abundance per plant, whereas P addition stimulated it by decreasing the plant density yet stimulating height of plants and their seed number per inflorescence. Our results indicate seed production is limited not by P but rather by N in the temperate steppe, whereas seed production will be increased by P addition when N availability is improved. These findings enable a better understanding of plant reproduction dynamics of steppe ecosystems under intensified nutrient enrichment and can inform their improved management in the future.