Role of Silicon in Counteracting Cadmium Stress in Pea Plants (Pisum sativum L.): Insights Into Cadmium Binding Mechanisms and Pectin Methylesterase Activity

Abstract 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.

Metal tolerance and Cd phytoremoval ability in Pisum sativum grown in spiked nutrient solution

Silicon’s Influence on Polyphenol and Flavonoid Profiles in Pea (<i>Pisum sativum</i> L.) under Cadmium Exposure in Hydroponics: A Study of Metabolomics, Extraction Efficacy, and Antimicrobial Properties of Extracts

The current study aimed to investigate the impact of silicon (Si) supplementation in the form of Na₂SiO₃ on the metabolome of peas under normal conditions and following exposure to cadmium (Cd) stress. Si is known for its ability to enhance stress tolerance in various plant species, including the mitigation of heavy metal toxicity. Cd, a significant contaminant, poses risks to both human health and the environment. The study focused on analyzing the levels of bioactive compounds in different plant parts, including the shoot, root, and pod, to understand the influence of Si supplementation on their biosynthesis. Metabolomic analysis of pea samples was conducted using a targeted HPLC/MS approach, enabling the identification of 15 metabolites comprising 9 flavonoids and 6 phenolic acids. Among the detected compounds, flavonoids, such as flavon and quercetin, along with phenolic acids, including chlorogenic acid and salicylic acid, were found in significant quantities. The study compared Si supplementation at concentrations of 1 and 2 mM, as well as Cd stress conditions, to evaluate their effects on the metabolomic profile. Additionally, the study explored the extraction efficiency of three different methods: accelerated solvent extraction (ASE), supercritical fluid extraction (SFE), and maceration (MAC). The results revealed that SFE was the most efficient method for extracting polyphenolic compounds from the pea samples. Moreover, the study investigated the stability of polyphenolic compounds under different pH conditions, ranging from 4.0 to 6.0, providing insights into the influence of the pH on the extraction and stability of bioactive compounds.

Znaczenie krzemu dla wybranych gatunków roślin o znanych właściwościach cytotoksycznych

Krzem (Si) jest pierwiastkiem występującym w dużych ilościach w skorupie ziemskiej. Niektóre rośliny, takie jak pszenica pobierają Si z gleby i akumulują go w swoich tkankach w większych ilościach niż np. groch czy lucerna. Co ciekawe, suplementacja krzemem wpływa na zwiększenie plonu tych roślin. Ponadto, w wielu przypadkach Si niweluje negatywne skutki działania stresów biotycznych i abiotycznych, co wskazuje na uruchomienie w roślinach procesów, być może poprzez produkcję związków o charakterze regeneracyjnym lub obronnym. Z drugiej strony pszenica, groch i lucerna są roślinami o znanych właściwościach cytotoksycznych. Poszukiwanie związków bioaktywnych pochodzenia roślinnego o potencjalnie pozytywnym wpływie, jest zagadnieniem o dużym znaczeniu zarówno poznawczym jak i praktycznym, ze względu na możliwość wykorzystania takich związków w leczeniu wielu chorób człowieka. Prezentowana praca przedstawia aktualny stan wiedzy na temat pobierania, transportu oraz efektów suplementacji krzemem roślin poddawanych stresom biotycznym i abiotycznym oraz właściwości cytotoksycznych pszenicy, grochu i lucerny. Słowa kluczowe: krzem, pszenica, groch, lucerna, stresy biotyczne i abiotyczne, cytotoksyczność

Fe3O4 nanoparticles and IAA auxin affect secondary metabolism over time without altering genetic stability in chrysanthemum

This research studied the impact of bare iron oxide nanoparticles (Fe₃O₄ NPs), citrate-stabilized iron oxide nanoparticles (Fe₃O₄CA NPs), and indole-3-acetic acid (IAA) on the genetic stability and metabolic activity of Chrysanthemum × morifolium (Ramat.) Hemsl. plants obtained from synthetic seeds. For this purpose, axillary buds of chrysanthemum 'Richmond' were embedded in 3% calcium alginate supplemented with NPs and IAA, either singularly or in combination. Next, the synthetic seeds were stored at 4 °C in the dark (for eight weeks) on an agar-water medium and then transferred to room temperature for 30 or 60 days. Next, the germinated seeds were transplanted to the greenhouse until the plants were fully flowering. The total polyphenol content (TPC) was determined in the leaves and inflorescences of the plants. Moreover, the content of anthocyanins was measured in the inflorescences. RAPD markers were used to assess the genetic stability of plants. Most treatments stimulated the accumulation of polyphenols in the leaves of chrysanthemum by as much as 59% after 30 days, and up to 28% after 60 days. Fe₃O₄NPs and IAA + Fe₃O₄CA NPs stimulated the biosynthesis of polyphenols and anthocyanins in the inflorescences after 30 days of treatment (by 36% and 68%, respectively); however, a decline in the content of these compounds (22-33%) was reported after 60 days in most experimental objects, except for Fe₃O₄CA NPs and IAA + Fe₃O₄CA NPs. The inflorescences of plants treated with nanoparticles usually exhibited a larger diameter than the control, but only after a shorter exposure to the analyzed factors. In contrast, prolonged treatment resulted in an opposite effect. The genetic uniformity of the plants was confirmed as no polymorphism was detected in 2160 RAPD markers.

Genetic Stability and Photosystem II Functioning of In Vitro-Recovered Lamprocapnos spectabilis (L.) Fukuhara After ZnO + Ag Nanoparticles or Melatonin Exposure During Vitrification—Preliminary Study

The success of plant tissue cryopreservation strongly depends on maximizing explant survival during storage in liquid nitrogen and recovery, which requires species-specific protocol optimization and ongoing refinement. This study examined the effect of Plant Vitrification Solution 3 (PVS3) supplemented with nanoparticles (NPs) or melatonin (MEL) on the recovery of Lamprocapnos spectabilis (L.) Fukuhara explants after cryostorage. Treatments with ZnO + Ag NPs, as well as different MEL concentrations, were applied to evaluate their influence on explant survival, photosynthetic efficiency, and genetic stability. The highest recovery (40–44%) was obtained with PVS3 containing 50 mg L−1 ZnO + 0.1% Ag NPs and PVS3 supplemented with 8 mg L−1 MEL, which was 17.5–20% higher than in the control. These treatments, however, did not ensure the highest photosynthetic efficiency of recovered plants. PVS additives likely support recovery by slowing metabolism and reducing oxidative stress, with lower photosynthetic activity suggesting a lag phase in plastid regeneration. Using the Start Codon Targeted (SCoT) marker system, no significant genetic alterations were detected in recovered plants of any tested variant. These findings demonstrate the feasibility of optimizing cryopreservation protocols for L. spectabilis and encourage further research on combined NPs and MEL treatments or alternative nanocarriers.