Agricultural soil degradation is occurring at unprecedented rates, not only as an indirect effect of climate change (CC) but also due to intensified agricultural practices which affect soil properties and biodiversity. Therefore, understanding the impacts of CC and soil degradation on plant physiology is crucial for the sustainable development of mitigation strategies to prevent crop productivity losses. The amino acid proline has long been recognized for playing distinct roles in plant cells undergoing osmotic stress. Due to its osmoprotectant and redox-buffering ability, a positive correlation between proline accumulation and plants’ tolerance to abiotic stress has been pointed out in numerous reviews. Indeed, proline quantification is used systematically by plant physiologists as an indicator of the degree of tolerance and a measurement of the antioxidant potential in plants under stressful conditions. Moreover, the exogenous application of proline has been shown to increase resilience to several stress factors, including those related to soil degradation such as salinity and exposure to metals and xenobiotics. However, recent data from several studies often refer to proline accumulation as a signal of stress sensitivity with no clear correlation with improved antioxidant activity or higher stress tolerance, including when proline is used exogenously as a stress reliever. Nevertheless, endogenous proline levels are strongly modified by these stresses, proving its involvement in plant responses. Hence, one main question arises—is proline augmentation always a sign of improved stress resilience? From this perspective, the present review aims to provide a more comprehensive understanding of the implications of proline accumulation in plants under abiotic stress induced by soil degradation factors, reinforcing the idea that proline quantification should not be employed as a sole indicator of stress sensitivity or resilience but rather complemented with further biochemical and physiological endpoints.

Eucalyptus globulus Labill. is a widespread exotic species that contributes to the formation of fire-prone environments, a great concern under climate change conditions. Therefore, sustainable practices to help locals managing eucalyptus stands are needed. In this perspective, harnessing eucalyptus’ specialized metabolism as a source of allelochemicals can be a promising approach for weed control. Thus, the main goals of this work were to evaluate the herbicidal potential of post-fire regenerated E. globulus leaves against Portulaca oleracea L. and to unravel the physiological mechanisms behind this phytotoxic action. For this, aqueous extracts of fresh (FLE; 617 g FW L⁻¹) or oven-dried leaves (DLE; 250 g DW L⁻¹) were foliar-sprayed at different dilutions in purslane seedlings. After five weeks, results revealed that DLE at the highest dose detained the greatest herbicidal activity, affecting purslane growth and cellular viability. Moreover, biochemical data pointed towards an overproduction of reactive oxygen species, causing harsh oxidative damage in roots, where the upregulation of important cellular players, like sugars, amino acids, and proline, was not able to reestablish redox homeostasis. Overall, this study proved that dried leaves from young E. globulus had potent herbicidal properties against P. oleracea and can represent a feasible strategy for weed management.

As available tools for crop disease management are scarce, new, effective, and eco-friendly solutions are needed. So, this study aimed at assessing the antibacterial activity of a dried leaf Eucalyptus globulus Labill. aqueous extract (DLE) against Pseudomonas syringae pv. tomato (Pst), Xanthomonas euvesicatoria (Xeu), and Clavibacter michiganensis michiganensis (Cmm). For this, the inhibitory activity of different concentrations of DLE (0, 15, 30, 45, 60, 75, 90, 105, 120, 135, and 250 g L⁻¹) was monitored against the type strains of Pst, Xeu, and Cmm through the obtention of their growth curves. After 48 h, results showed that the pathogen growth was strongly inhibited by DLE, with Xeu the most susceptible species (15 g L⁻¹ MIC and IC₅₀), followed by Pst (30 g L⁻¹ MIC and IC₅₀), and Cmm (45 and 35 g L⁻¹ MIC and IC₅₀, respectively). Additionally, using the resazurin assay, it was possible to verify that DLE considerably impaired cell viability by more than 86%, 85%, and 69% after Pst, Xeu, and Cmm were incubated with DLE concentrations equal to or higher than their MIC, respectively. However, only the treatment with DLE at 120 g L⁻¹ did not induce any hypersensitive response in all pathogens when treated bacterial suspensions were infiltrated onto tobacco leaves. Overall, DLE can represent a great strategy for the prophylactic treatment of tomato-associated bacterial diseases or reduce the application of environmentally toxic approaches.

Allelopathy, the inhibition of neighbouring plant growth by certain plants, can be particularly useful if applied in a targeted way for weed management. So, this study aimed to assess and characterize the herbicidal activity of fresh and dried leaves from young Eucalyptus globulus Labill. trees applied as a soil amendment. For this, fresh and dried leaves (FL and DL, respectively) were incorporated into the soil at different concentrations (0, 1, 5, and 10% w/w), where Portulaca oleracea L. seeds were sown. After 5 weeks of exposure, results revealed that the soil incorporation of DL at 10% (w/w) presented the strongest herbicidal properties, inhibiting seed germination by 63% and inducing the loss of cell viability. To unravel the possible mode of action and the main targets at both cellular and subcellular levels, an in vitro experiment was performed. Purslane seeds were sown in a nutritive medium containing different dilutions of an aqueous extract prepared with dried eucalyptus leaves. After 5 days of exposure, germinated seedlings were processed for transmission electron microscopy and histological analyses as well as for reactive oxygen species (ROS) in vivo detection by confocal laser scanning microscopy. Results revealed that the allelochemical release from DL induced ROS overproduction, resulting in the loss of cell integrity and organization, which was characterized by damage to several cellular sub-structures, along with enhanced accumulation of lipid droplets. Overall, the incorporation of DL into the soil can represent a sustainable alternative to reduce synthetic herbicide application and subsequent environmental contamination.

Along with climate change, the native forest replacement by exotic species, such as Eucalyptus globulus, is contributing to a highly fire-prone environment. Since E. globulus detains several post-fire regeneration strategies, sustainable practices are needed to manage eucalyptus stands. Thus, eucalyptus allelopathic potential can be used for weed control. Therefore, this study aimed at assessing the herbicidal potential of post-fire regenerated E. globulus leaves in Portulaca oleracea, and unraveling the main physiological processes disturbed by biocide application. For this, an aqueous extract prepared with fresh leaves (FLE; 617 gfresh weightL-1) and other with oven-dried leaves (DLE; 250 gdry weightL-1) were prepared and foliar-sprayed twice-a-week at different dilutions in 7-days-old purslane plants. As positive control, glyphosate was used. After five weeks, results revealed that DLE at the highest dose detained the greatest herbicidal activity against P. oleracea. To understand how DLE impacted weed physiology, several biochemical and redox-related parameters were evaluated in purslane plants treated with DLE highest dose. Results suggested an overproduction of hydrogen peroxide, causing severe oxidative damage in roots. Overall, this study showed that young E. globulus dried leaves had powerful herbicidal properties against P. oleracea and can represent a feasible approach for weed management, while reducing fire hazard.

BACKGROUND: Essential oils (EOs) from Eucalyptus globulus Labill. leaves are widely recognized for their biological properties. However, the influence of leaf age on EOs chemical composition and bioactivity remains unclear. This study aimed to characterize the chemical profiles and biopesticidal potential of EOs extracted from juvenile leaves from young trees (YEEO) and adult leaves from mature trees (AEEO) against relevant agricultural pests and pathogens. RESULTS: Metabolomic profiling revealed similar overall compound diversity between YEEO and AEEO. YEEO contained higher levels of α‐pinene and β‐pinene, whereas AEEO was richer in oxygenated compounds, such as 1,8‐cineole and trans‐pinocarveol. Herbicidal activity was tested against Portulaca oleracea and Solanum nigrum in pre‐ and post‐emergent assays, showing strong post‐emergent effects with 100% mortality at the highest concentrations. Both EOs also displayed dose‐dependent antibacterial activity, with Clavibacter michiganensis subsp. michiganensis being the most susceptible, followed by Xanthomonas euvesicatoria and Pseudomonas syringae pv. tomato . No antifungal activity was observed against Alternaria alternata or Botrytis cinerea , but both EOs exhibited potent insecticidal activity against Phthorimaea absoluta larvae, achieving total mortality at the highest concentration (50% v/v) and low LC₅₀ (15.2% v/v for YEEO and 14% v/v for AEEO) and LC₉₀ values (41.4% v/v for YEEO and 38.5% v/v for AEEO). CONCLUSION: Despite their chemical differences, YEEO and AEEO showed comparable herbicidal, antibacterial, and insecticidal effects, highlighting the feasibility of large‐scale EO production, especially by valorizing adult leaves, a by‐product of the paper and furniture industries. These findings highlight the potential of E. globulus EOs as bioactive agents against weeds, insects, and bacteria; however, further field studies are required to evaluate their practical applicability. © 2026 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.