The widespread replacement of conventional plastics with biodegradable alternatives raises questions about their long-term effects in agricultural soils. We investigated the impact of microplastics (MPs) cryo-milled from home-compostable (PBAT_HOME) and industrial-compostable (PBAT_IND) polybutylene adipate terephthalate bags and compared it to the toxicity of MPs from conventional polyethylene (PE) bags. Sunflowers (Helianthus annuus L.) were grown in pots with soil spiked with 0 %, 0.05 %, 0.5 %, and 1.0 % (w/w) MPs for eight weeks under a 16/8 day-night photoperiod at room temperature (22/18 °C). Plant responses differed notably between biodegradable and conventional MPs as revealed by two-way hierarchical clustering analysis: both PBAT_HOME and PBAT_IND significantly reduced shoot and root biomass at 0.5 % and 1 %, while PE had no effect. At higher PBAT concentrations, proline levels increased, consistent with activation of drought-like stress response pathways that merit confirmation with additional molecular biomarkers. Soil water holding capacity increased at 1 % of all three MPs, indicating a lower water availability for plants in the MP-spiked soil. pH was slightly increased at 1 % PBAT_HOME and significantly at 1 % PBAT_IND soil. Despite differences in particle size, polymer composition, and starch content, no single factor explained the observed effects, suggesting a combined influence. These results highlight that biodegradable MPs can alter soil properties and trigger physiological responses in plants, emphasizing the need to assess their ecological impacts, especially in agricultural systems where soil health and resilience are critical for crop production.

The increasing use of biodegradable plastics (BPs) as alternatives to conventional plastics (CPs) is leading to the accumulation of biodegradable microplastics (BMPs) in terrestrial environments. Contrary to assumptions of rapid degradation, BMPs can persist in soil long enough to interact with key biological processes. This review advances the field by proposing a mechanistic framework linking BMP aging and degradation, soil physicochemical transformations, plastisphere assembly, rhizosphere interactions, and plant responses, and by critically evaluating the sources of inconsistency across studies. We show that divergent effects of BMPs can be best explained by four interacting determinants: polymer chemistry and additive composition, aging-driven surface transformations, soil physicochemical properties, and rhizosphere processes including plant-mediated effects. Through these coupled pathways, BMPs can alter aggregation, pore architecture, pH, enzyme activity, and carbon and nutrient cycling, thereby reshaping the soil environment in which microorganisms and roots interact. BMP surfaces can also act as dynamic microbial niches that promote biofilm formation, shift microbial community composition and function, and under certain conditions may facilitate pollutant transport, pathogen persistence, and horizontal gene transfer. Plant responses to BMPs are predominantly indirect and emerge from rhizosphere-mediated processes, which helps explain the wide variability in reported plant responses, ranging from subtle metabolic changes to pronounced growth inhibition. However, current evidence is constrained by short-term studies and insufficient consideration of aged materials. Biodegradability should therefore not be equated with low ecological risk in soils. Progress in this field requires integrative approaches linking BMP properties, plastisphere dynamics, and plant-soil interactions over time.

Noccaea species (formerly Thlaspi) are Brassicaceae plants renowned for their capacity to hyperaccumulate zinc (Zn), cadmium (Cd), and nickel (Ni), which has made them model systems in studies of metal tolerance, phytoremediation, and plant adaptation to extreme environments. While their physiological and genetic responses to metal stress are relatively well characterised, the extent to which these traits influence microbiome composition and function remains largely unexplored. These species possess compact genomes shaped by ancient whole-genome duplications and rearrangements, and such genomic traits may influence microbial recruitment through changes in secondary metabolism, elemental composition, and tissue architecture. Here, we synthesise the current findings on how genome size, metal hyperaccumulation, structural adaptations, and glucosinolate diversity affect microbial communities in Noccaea roots and leaves. We review evidence from bioimaging, molecular profiling, and physiological studies, highlighting interactions with bacteria and fungi adapted to metalliferous soils. At present, the leaf microbiome of Noccaea species remains underexplored. Analyses of root microbiome, however, reveal a consistent taxonomic core dominated by Actinobacteria and Proteobacteria among bacterial communities and Ascomycetes, predominantly Dothideomycetes and Leotiomycetes among fungi. Collectively, these findings suggest that metal-adapted microbes provide several plant-beneficial functions, including metal detoxification, nutrient cycling, growth promotion, and enhanced metal extraction in association with dark septate endophytes. By contrast, the status of mycorrhizal associations in Noccaea remains debated and unresolved, although evidence points to functional colonisation by selected fungal taxa. These insights indicate that multiple plant traits interact to shape microbiome assembly and activity in Noccaea species. Understanding these dynamics offers new perspectives on plant–microbe co-adaptation, ecological resilience, and the optimisation of microbiome-assisted strategies for sustainable phytoremediation.

Noccaea species (formerly Thlaspi) are Brassicaceae plants renowned for their capacity to hyperaccumulate zinc (Zn), cadmium (Cd), and nickel (Ni), which has made them model systems in studies of metal tolerance, phytoremediation, and plant adaptation to extreme environments. While their physiological and genetic responses to metal stress are relatively well characterised, the extent to which these traits influence microbiome composition and function remains largely unexplored. These species possess compact genomes shaped by ancient whole-genome duplications and rearrangements, and such genomic traits may influence microbial recruitment through changes in secondary metabolism, elemental composition, and tissue architecture. Here, we synthesise current findings on how genome size, metal hyperaccumulation, structural adaptations, and glucosinolate diversity affect microbial communities in Noccaea roots and leaves. We review evidence from bioimaging, molecular profiling, and physiological studies, highlighting interactions with bacteria and fungi adapted to metalliferous soils. While mycorrhizal associations remain debated, data suggest functional colonisation by selected fungal taxa. Taken together, these insights indicate that multiple plant traits interact to shape microbiome assembly and activity in Noccaea species. Understanding these dynamics offers new perspectives on plant–microbe co-adaptation, ecological resilience, and the optimisation of microbiome-assisted strategies for sustainable phytoremediation.

Microplastics are increasingly accumulating in agricultural soils, where they may alter microbial communities and plant–microbe interactions. Although biodegradable plastics are often considered environmentally preferable alternatives to conventional plastics, they may introduce chemically and biologically accessible components into soil. However, it remains unclear whether microplastics derived from these products alter rhizosphere soil microbiomes differently from conventional polyethylene (PE). We compared microplastics produced from a conventional PE bag and two biodegradable starch-containing poly(butylene adipate-co-terephthalate) bags intended for home (PBAT_HOME) or industrial composting (PBAT_IND). Microplastic particles were incorporated into soil at 0.5% and 1.0% (w/w dry soil), sunflower (Helianthus annuus L.) was grown for eight weeks, and bacterial and fungal communities and their annotated gene repertoires were characterized using shotgun metagenomics. Within the tested concentration range, microplastic polymer composition explained more variation in community composition than concentration. Namely, communities exposed to either PBAT type were distinct from the control and PE treatments, with fungal composition showing the clearest response. PBAT-associated indicator taxa included genera containing members linked in the literature to decomposition or anaerobic metabolism, although fungal trophic-mode ratios did not differ significantly among treatments. PBAT_IND was associated with KEGG orthologs (KOs) involved in methane metabolism and carbohydrate transport, whereas PBAT_HOME was associated with KOs related to lipid and fatty-acid metabolism. PE showed a contrasting gene repertoire associated with nitrogen acquisition and assimilation. These metagenomic patterns indicate shifts in functional potential rather than measured biogeochemical activity. Overall, starch-containing PBAT microplastics acted as biologically reactive soil inputs, selecting microbial communities and annotated gene repertoires distinct from those associated with PE. This study provides testable hypotheses about carbon and nitrogen processing induced by PBAT microplastics in planted soil.