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Apple replant disease (ARD) is a complex agricultural problem caused by multiple stressors that can lead to increased reactive oxygen species (ROS) levels and limited nutrient utilization in plants. However, existing countermeasures cannot effectively address this challenge. Here, we used Malus hupehensisas a test organism to investigate whether the pleiotropic molecule dopamine can alleviate ARD using pot experiments. Exogenous application of 100 μmol L–1dopamine significantly promoted the growth of apple seedlings in the replanted soil, with a relative growth rate increase of 17.44%. Our results revealed two major pathways by which dopamine regulates ARD resistance in apple trees. First, dopamine effectively reduces the level of ROS and activates the expression of genes related to nitrogen (N) transport and metabolism. Among those genes, MdNLP5, MdNRT1.1, MdNLP2, MdNRT2.5, MdNLP3, MdNRT2.4, MdNADH-GAGOT, and MdFd-GAGOTwere strongly regulated by dopamine. These regulatory effects promoted the uptake and utilization of soil N by the plants. Second, dopamine improved the physical and chemical properties, enhanced microbial community diversity, and promoted mutual cooperation between microbial communities in the soil. Furthermore, dopamine altered the microbial structure of rhizosphere soil (upregulating Clostridiales, Gaiellales, Sordariales and Mortierellales; downregulating Micrococcales, Longimicrobiales, Hypocreales and Cystobasidiales). Notably, dopamine significantly upregulated the abundances of Gaiellaand Mortierella, both of which were positively correlated with soil urease activity, soil available N content, plant growth and N uptake. Dopamine also significantly downregulated the abundance of the plant pathogen Gibberella(by 11.71-fold) in replant soil. Our results provide insights into the mechanisms by which dopamine promotes ARD resistance, and can promote the sustainable development of the apple industry.

Phloridzin significantly influences apple plant growth, development, and resistance to environmental stresses by engaging in various metabolic processes. Its excessive accumulation in soil, attributed to continuous monoculture practices, not only inhibits plant growth but also disrupts the rhizosphere microbial community. This study aims to explore the remedial effects of dopamine, a known antioxidant and stress resistance modulator in plants, on the adverse impacts of phloridzin stress in apple. Through hydroponic and pot experiments, it was demonstrated that dopamine significantly mitigates the growth inhibition caused by phloridzin stress in apple by reducing reactive oxygen species levels and enhancing photosynthesis and nitrogen transport. Additionally, dopamine reduced phloridzin concentrations in both the rhizosphere and roots. Furthermore, dopamine positively influences the structure of the rhizosphere microbial community, enriching beneficial microbes associated with nitrogen cycling. It increases the potential for soil nitrogen degradation and fixation by upregulating the abundance of ureC, GDH, and nifH, as revealed by metagenomic analysis. This aids in alleviating phloridzin stress. The study reveals dopamine’s pivotal roles in modulating rhizosphere ecology under phloridzin stress and suggests its potential in sustainable apple cultivation practices to counter ARD and enhance productivity.

There is a growing demand for degradable membranes with sufficient mechanical properties to guide tissue regeneration in dental surgery. In the present work, a two-stage rolling process in which the first rolling stage (FRS) adopted a reduction rate of 30% for six passes at various temperatures, while the second rolling stage was rolling at 200 °C for two passes, was employed to prepare a 150 μm-grade Mg–2.0Zn–0.5Y–0.5Nd (ZE21B) Mg alloy sheets for guided tissue regeneration membrane. The microstructure of the thin sheets was gradually refined with increasing rolling passes, and the thin sheets that were rolled at different FRS temperatures exhibit an ellipse texture. The thin sheets rolled at 350 °C for FRS show low elongation due to premature fracture caused by the coarse second phase particles. On account of uniform and fine grains, the thin sheets rolled at 400 °C for the FRS have proper mechanical properties: yield strength of 214.6 ± 8.5 MPa, ultimate tensile strength (UTS) of 246.8 ± 10.3 MPa and elongation to failure of 28.3 ± 1.2%. When rolling at 450 °C for FRS, proper ductility of the thin sheets has been acquired, followed by a decline in UTS since a bimodal structure with fine and coarse grain was developed. Immersion tests demonstrated the FRS temperature had no significant effect on the corrosion behavior and corrosion rate of Mg alloy sheets after 7 days’ immersion in artificial saliva solution. This research has great significance for the production of degradable Mg sheets for guided tissue regeneration membrane.

Dopamine has demonstrated promise as a stress-relief substance. However, the function of dopamine in Cd tolerance and its mechanism remains largely unknown. The current study was performed to investigate the mechanism of dopamine on alleviating apple Cd stress through regular application of CdCl2and dopamine solution to potting soil. The results indicated that dopamine significantly reduced reactive oxygen species (ROS) and Cd accumulation and alleviated the inhibitory effect of Cd stress on the growth of apple plants through activation of the antioxidant system, enhancement of photosynthetic capacity, and regulation of gene expression related to Cd absorption and detoxification. The richness of the rhizosphere microbial community increased, and community composition and assembly were affected by dopamine treatment. Network analysis of microbial communities showed that the numbers of nodes and total links increased significantly after dopamine treatment, while the keystone species shifted. Linear discriminant analysis effect size indicated that some biomarkers were significantly enriched after dopamine treatment, suggesting that dopamine induced plants to recruit potentially beneficial microorganisms (Pseudoxanthomonas, Aeromicrobium, Bradyrhizobium, Frankia, Saccharimonadales, Novosphingobium, and Streptomyces) to resist Cd stress. The co-occurrence network showed several metabolites that were positively correlated with relative growth rate and negatively correlated with Cd accumulation, suggesting that potentially beneficial microorganisms may be attracted by several metabolites (L-threonic acid, profenamine, juniperic acid and (3β,5ξ,9ξ)-3,6,19-trihydroxyurs-12-en-28-oic acid). Our results demonstrate that dopamine alleviates Cd stress in apple trees by recruiting beneficial microorganisms to enhance the physiological resilience revealed. This study provides an effective means to reduce the harm to agricultural production caused by heavy metals.

The paper explores the new method of improving the workability of materials in the dieless drawing processes. The proposed method is based on the implementation of a multi-pass incremental deformation. Moreover, in each pass, strain and strain rate sensitivity of flow stress should be positive and significant. An approach based on the finite element calculation of instability coefficient of plastic deformation and simultaneous modeling of material ductility were applied for prediction of the workability. Two dieless drawing processes have been investigated. The difference was related to the heating system—induction heating and laser heating. FE simulations and experimental tests for three materials, two magnesium alloys (MgCa0.8 and MgNi19) and pure copper were performed. It was shown that the most effective increase in workability by multi-pass deformation can be achieved using laser dieless drawing. This is possible due to the shorter heating area and, as a consequence, the larger strain rate, which leads to better stability of the deformation process.