Katarzyna Głowacka

Electrical stimulation is increasingly explored as a strategy to accelerate the development of electroactive biofilms in microbial fuel cells (MFCs), yet its integration with photosynthetic MFCs (pMFCs) remains insufficiently understood. This study evaluated how short-term anodic stimulation (0.5–5 V, 4 days) affects biofilm formation and COD removal, and how subsequent operation with photosynthetic cathodes—Chlorella sp., Arthrospira platensis and Tetraselmis subcordiformis—modulates anodic microbial communities and functional potential. Stimulation at 1 V yielded the best activation effect, resulting in the highest voltage output, power density and fastest COD removal kinetics, whereas 5 V inhibited biofilm development. During pMFC operation, Chlorella produced the highest voltage (0.393 ± 0.064 V), current density (0.14 ± 0.02 mA·cm⁻²) and Coulombic efficiency (~19%). Arthrospira showed moderate performance, while Tetraselmis generated no current despite efficient COD removal. 16S rRNA sequencing revealed distinct cathode-driven community shifts: Chlorella enriched facultative electroactive taxa, Arthrospira promoted sulfur-cycling bacteria and Actinobacteria, and Tetraselmis induced strong methanogenic dominance. Functional prediction and qPCR confirmed these trends, with Chlorella showing increased pilA abundance and Tetraselmis displaying enriched methanogenic pathways. Overall, the combined use of optimal anodic stimulation and photosynthetic cathodes demonstrates that cathodic microalgae strongly influence anodic redox ecology and energy recovery, with Chlorella-based pMFCs offering the highest electrochemical performance.

Silicon (Si) has emerged as a promising tool for mitigating the negative effects of biotic and abiotic stresses, such as caused by heavy metals, on plants. The aim of the study was to summarize knowledge about the mechanisms underlying the interaction between silicon and cadmium. This review first discusses silicon compounds in plant physiology, then examines mechanisms of silicon–cadmium interaction, including antioxidant defense, metal chelation, nutrient transport, molecular responses, subcellular changes, and future directions. Recent studies show that various forms of Si, such as conventional Si and Si-nanoparticles (Si NPs), can have various effects on the ability of a plant to absorb and utilize Si for protection. Silicon, taken up mainly as soluble orthosilicic acid (H₄SiO₄) and Si NPs, can be absorbed by plants and subsequently deposited predominantly in cell walls. It has been found that Si and Si NPs increase the activity of antioxidant enzymes, including CAT, SOD, and POD, in plants under cadmium (Cd) stress. Furthermore, Si reduces the expression of Cd transport-related genes, including OsNRAMP5 and OsHMA2 in rice. It has also been shown that supplementation with Si and Si NPs in plants under Cd stress reduces the Cd content in their tissues and changes the uptake of elements necessary for the proper functioning of the plant organism. Furthermore, Si supplementation increases the content of pectins, which are involved in the binding and neutralization of Cd. The following overview highlights the importance of both Si and SiNPs in neutralizing the harmful effects of Cd on the environment and agriculture.

The results of our recent research revealed that biologically synthesized silver nanoparticles (bio-AgNPs) applied to several-day-old pea (Pisum sativum L.) plants or used for seed nanopriming protected pea plants against selected fungal pathogens. However, the susceptibility of pea to bio-AgNPs during seed germination remains mostly unknown. Therefore, in this study, we investigated the cells’ viability, ROS generation, total antioxidant capacity, the activity of selected antioxidant enzymes, and changes in the polar metabolite profiles of 4-day-old pea seedlings developed in water (control) and water suspensions of bio-AgNPs (at 50 and 200 mg/L). The bio-AgNPs did not negatively affect pea seeds’ germination, early seedlings’ growth, and root tips cells’ viability (at both tested concentrations). In the root, the bio-AgNPs at a lower concentration (50 mg/L) stimulated ROS generation. Nanoparticles enhanced peroxidase activity in root and the total antioxidant capacity in epicotyl. Increased levels of malate, phosphoric acid, proline, GABA, and alanine were observed in root and epicotyl of pea seedlings developed at 50 mg/L of bio-AgNPs. A higher concentration affected the tricarboxylic acid cycle and nitrogen metabolism. Bio-AgNPs alerted oxidative homeostasis and primary metabolism of pea seedlings but did not exceed a certain threshold limit and thus did not injure pea at an early stage of seedling development.

The impact of tetracycline on the soil and rhizosphere microbiome of lettuce was analyzed. Soil was collected from an agricultural field regularly fertilized with manure, and tetracycline was added at two concentrations (5 mg/kg and 25 mg/kg). In untreated soil, dominant bacteria included Proteobacteria (43.17%), Bacteroidota (17.91%), and Firmicutes (3.06%). Tetracycline addition caused significant shifts in the microbiome composition, notably increasing Actinobacteriota (22%) and favoring Mycobacterium tuberculosis (low concentration) and Mycobacterium holsaticum (high concentration). Proteobacteria decreased by 21%, possibly indicating antibiotic resistance development. An increase in Firmicutes, particularly Bacillales, suggested a selection for resistant strains. In the lettuce rhizosphere, tetracycline-induced changes were less pronounced than in soil. Proteobacteria remained dominant, but taxa like Burkholderiales and Chitinophagales increased in response to tetracycline. The rise in chitin-degrading bacteria might result from fungal overgrowth linked to the bacteriostatic effects of tetracycline. Pathogens such as M. tuberculosis, observed in the soil, were not detected in the lettuce rhizosphere.

Purpose: The aim of this study was to investigate the role of silicon (Si) in counteracting a cadmium (Cd) stress to pea plants (Pisum sativum L.) and to identify the mechanism by which Cd is bound within pea roots. Methods: These goals were achieved through (i) a histochemical study of Cd localization in pea roots, (ii) spectrophotometric determination of pectin content and the activity of pectin methylesterase (PME), (iii) speciation of Cd extracted from pea roots conducted through size exclusion chromatography (SEC) and inductively coupled plasma mass spectrometry (ICP/MS). Results: Cd was found mainly in the root stele of the Cd-stressed plants. The pectin content and PME activity were lower in the Cd-stressed plants, but Si supplementation reversed these effects. Selectivity was noticed in Cd extraction efficiency with water being the least effective and enzymatic-assisted extraction proving to be the most effective. Speciation analysis revealed significant heterogeneity in molar mass, ranging from approximately 295 to 95 kDa. Galacturonic acid was identified the dominant species responsible for Cd binding. The choice of solvent for extraction markedly influenced the Cd binding profile, indicating shifts in the distribution of species’ molar mass and their relative concentrations in extracts. Conclusions: Si alleviates Cd toxicity in pea plants, and one of the mechanisms through which it operates involves increasing pectin levels and PME activity. Pectin plays an active role in Cd detoxification in the root cell walls, forming electrostatic bonds with Cd cations through its carboxyl groups.

Cadmium (Cd) is a key stress factor that affects plant development. To examine the influence of Cd stress, we analysed the tissue localisation of polysaccharides (Periodic Acid Schiff reaction), qualitative and quantitative changes in soluble carbohydrates (High-Resolution Gas Chromatography), and the expression of the galactinol synthase (PsGolS) and raffinose synthase (PsRS) genes in 4-week-old Pisum sativum L. ‘Pegaz’. The plants were treated with 10, 50, 100, and 200 µM CdSO₄ for one week and analysed on the 1st, 7th, and 28th days after Cd application. Pea as an excluder plant accumulated Cd mainly in the roots. Cd induced starch grain storage in the stems and the accumulation of soluble carbohydrates in roots and shoots after 28 days of Cd treatment. In controls, soluble carbohydrate levels decreased during the plant growth. In addition, Cd increased galactinol and raffinose levels, indicating their important role in response to Cd stress in peas. Moreover, the analysis confirmed that the expression of PsGolS was induced by Cd. Overall, the results of the distribution of carbohydrates in pea plants, together with the inhibition of seed production by Cd, indicate that plants tend to allocate energy to stress response mechanisms rather than to reproductive processes.

In the presented study, the effects of cadmium (Cd) stress and silicon (Si) supplementation on the pea plant (Pisum sativum L.) were investigated. The tendency to accumulate cadmium in the relevant morphological parts of the plant (roots and shoots respectively)—bioaccumulation, the transfer of this element in the plant (translocation) and the physiological parameters of the plant through indicators of oxidative stress were determined. Model studies were carried out at pH values 6.0 and 5.0 plant growth conditions in the hydroponic cultivation. It was shown that Cd accumulates mostly in plant roots at both pH levels. However, the Cd content is higher in the plants grown at lower pH. The Cd translocation factor was below 1.0, which indicates that the pea is an excluder plant. The contamination of the plant growth environment with Cd causes the increased antioxidant stress by the growing parameters of the total phenolic content (TPC), polyphenol oxidase activity (PPO), the malondialdehyde (MDA) and lipid peroxidation (LP). The results obtained showed that the supplementation with Si reduces these parameters, thus lowering the oxidative stress of the plant. Moreover, supplementation with Si leads to a lower content of Cd in the roots and reduces bioaccumulation of Cd in shoots and roots of pea plants.

This review describes the role of silicon (Si) in plants. Methods of silicon determination and speciation are also reported. The mechanisms of Si uptake by plants, silicon fractions in the soil, and the participation of flora and fauna in the Si cycle in terrestrial ecosystems have been overviewed. Plants of Fabaceae (especially Pisum sativum L. and Medicago sativa L.) and Poaceae (particularly Triticum aestivum L.) families with different Si accumulation capabilities were taken into consideration to describe the role of Si in the alleviation of the negative effects of biotic and abiotic stresses. The article focuses on sample preparation, which includes extraction methods and analytical techniques. The methods of isolation and the characterization of the Si-based biologically active compounds from plants have been overviewed. The antimicrobial properties and cytotoxic effects of known bioactive compounds obtained from pea, alfalfa, and wheat were also described.

Modern integrated farming systems encourage the search for alternative (non-chemical), highly effective methods of plant protection. In this study, the fungistatic effect of fennel essential oil (FEO) and hop essential oil (HEO) on fungal growth and their ability to treat Fusarium wilt was investigated. The study was conducted in vitro and in pot experiments. The severity of infection was assessed by disease index (DI), presence of Fusarium culmorum gDNA (qPCR) and anatomical analyses of infected plant tissue using an optical (OM) and scanning electron microscope (SEM). Laboratory analyses showed that FEO inhibits mycelial growth of Fusarium fungi (F. avenaceum, F. culmorum, F. equiseti, F. oxysporum, F. poae, F. solani, F. sporotrichioides, F. tricinctum), Botrytis cinerea and Cylindrocarpon destructans more effectively than HEO. FEO at a concentration of 2000 ppm completely inhibited the growth of F. culmorum, F. poae and B. cinerea. Both essential oils reduced the severity of Fusarium wilt caused by F. culmorum in pea plants (DI, OM, SEM). The qPCR shows that both essential oils are also able to reduce the synthesis of trichothecenes in the tissues of infected pea plants. The results of the study suggest that FEO and HEO represent a broad spectrum bio-fungicidal agent that can be applied directly to plants at a concentration of 500 ppm, greatly reducing the level of infection.