Search Results (4)

Nickel (Ni) contamination threatens plant growth and ecosystem stability, and plant-growth-promoting rhizobacteria (PGPR) are sustainable bioremediation candidates. Here, we isolated and characterized a Ni-resistant PGPR strain, Microbacterium algeriense C14, from the rhizosphere of Zinnia elegans in Ni-contaminated soil. C14 exhibited exceptional Ni tolerance (up to 800 mg·L⁻¹), produced indole-3-acetic acid (IAA), and maintained pH homeostasis (8.3–8.7). XPS and XRD analyses confirmed a novel carboxylate-based precipitation mechanism: C14 secretes carboxyl-containing metabolites that coordinate with Ni²⁺ to form stable amorphous nickel–carboxylate complexes. Under Ni stress (50–600 mg·L⁻¹ for germination; 50–600 mg·kg⁻¹ soil for pot experiments), C14 inoculation increased the seed germination index by up to 47.3%, seedling root length by 36.9%, and mature plant aboveground fresh weight by 21.32%, while reducing plant Ni uptake by 38.7% (seedlings) and 49.9% (mature shoots). It also enhanced plant antioxidant-enzyme (SOD and POD) activities and soluble protein content, improved soil quality (pH +0.16–0.33 units, urease/acid phosphatase activities elevated), and reduced soil-available Ni by 23.7%. Additionally, C14 enriched Proteobacteria in the rhizosphere and modified microbial community structure. These results highlight M. algeriense C14 as a promising resource for Ni-contaminated soil remediation via integrated metal immobilization, growth promotion, and rhizosphere regulation. Full article

As a global environmental problem, biological invasion poses a serious threat to natural ecosystems. To explore the influence mechanism of Alternanthera philoxeroides (Mart.) Griseb on the growth and development of landscape plants, this study systematically analyzed the effects of extracts from different organs (stems, leaves, and roots) of A. philoxeroides on the seed germination and seedling growth of Zinnia elegans Jacq. by combining the Petri dish filter paper method with a pot experiment to reveal the potential mechanism of allelopathy. The results showed that the aqueous extract of A. philoxeroides inhibited the seed germination and seedling growth of Z. elegans. The high concentration (100 mg·mL⁻¹) of stem and leaf extracts significantly reduced the germination rate (by 99.10% and 90.65%) and seedling morphological parameters. The allelopathic inhibition increased with an increase in concentration, and the inhibitory effect of stem and leaf extracts was significantly stronger than that of root extracts. Aqueous extracts from the roots, stems, and leaves of A. philoxeroides at three concentrations (25, 50, and 100 mg·mL⁻¹) induced oxidative stress in seedlings, as evidenced by the elevated malondialdehyde (MDA) content and dysregulated activities of antioxidant enzymes. Specifically, superoxide dismutase (SOD) and catalase (CAT) activities exhibited a concentration-dependent trend of initial induction followed by subsequent inhibition, while root activity was significantly suppressed (p < 0.05), ultimately impairing seedling growth. The aqueous extracts of A. philoxeroides showed a concentration-dependent inhibitory effect on the seed germination and seedling growth of Z. elegans. High concentrations of stem and leaf extracts exerted a significant inhibitory effect on seedling growth, and this growth suppression was attributed to the induction of oxidative stress by the extracts. This study elucidated the phytotoxicity degree and physiological response mechanisms underlying the biochemical allelopathy of A. philoxeroides on Z. elegans. The findings provide a theoretical foundation for the selection of horticultural plant cultivars resistant to allelopathic stress and the development of management strategies for invasive plants. Full article

In organic farming, microwave irradiation can be used as an alternative to standard chemical seed treatment. The increase in temperature during this treatment may negatively affect the germination of low-quality seeds. The aim of the study was to evaluate the effect of microwaves on germination and the health of zinnia seeds using four seed samples varying in initial seed quality. Seeds were placed in a beaker with distilled water and irradiated at power output levels of 500, 650 and 750 W for 30, 35, 40, 45 and 50 s. Controls were untreated seeds, seeds treated with fungicide and seeds soaked in water for 30, 35, 40, 45 and 50 s. Germination and health tests were performed for controls and microwave-treated seeds. Analyzed samples differed in seed quality and response to microwave irradiation. Improvement in seed germination after microwave treatment was observed in three of the tested samples. The fungi Alternaria alternata, A. zinniae and Fusarium spp. prevailed on the seeds. Microwave treatment, especially at power outputs of 650 and 750 W, usually positively affected seed health, significantly increasing the number of seeds free of fungi, but when water temperature during treatment exceeded 60 °C significant deterioration in germination parameters was observed in all tested samples. Full article

The effects of biochar (BC) on seed propagation depend on the type of BC, BC incorporation rate, base substrate, and plant seed species. Limited research tested BC-compost mixes for seed propagation. High percentages (70% or 80%, by volume) of BC with vermicompost (VC) or chicken manure compost (CM) were evaluated to substitute a commercial propagation mix (control) in three experiments. Seeds, including basil, coleus, edamame, marigold, okra, petunia, radish, salvia, tomato, vinca, and zinnia in Experiments 1 and 2 had similar or higher emergence percentages (EPs) and emergence indexes (EIs) in both BC:VC mixes, while celosia, cowpea, corn, and pumpkin had lower EPs or EIs in either 8BC:2VC or 7BC:3VC mixes compared to the control. Seedling fresh weights in both BC:VC mixes were similar to the control except for vinca, pumpkin, marigold, and salvia. The BC:VC mixes had no negative effects on plant dry weights at 7 weeks after transplanting. In Experiment 3, BC:CM mixes suppressed the seed germination or seedling growth of coleus, corn, cowpea, marigold, petunia, pumpkin, radish, salvia, vinca, watermelon, and zinnia due to high pH and CM’s high electrical conductivity. Therefore, 7BC:3VC and 8BC:2VC can be used as seed propagation mix, while 7BC:3CM and 8BC:2CM are not recommended. Full article