Heavy metal and metalloid stress, particularly from toxic elements like cadmium (Cd), poses a growing threat to plant ecosystems, crop productivity, and global food security. Elevated concentrations of these contaminants can trigger cytotoxic and genotoxic effects in plants, severely impairing growth, development, and reproduction. In recent years, epigenetic mechanisms have emerged as crucial regulators of plant responses to heavy metal stress, offering novel insights and strategies for enhancing plant resilience in contaminated environments. This review synthesises current advances in the field of plant epigenetics, focusing on key modifications such as DNA methylation, histone acetylation and remodelling, chromatin dynamics, and small RNA-mediated regulation. These processes not only influence gene expression under metal-induced stress but also hold promise for long-term adaptation through transgenerational epigenetic memory. Recent developments in high-throughput sequencing and functional genomics have accelerated the identification of epigenetic markers associated with stress tolerance, enabling the integration of these markers into breeding programs and targeted epigenome editing strategies. Special attention is given to cadmium stress responses, where specific epigenetic traits have been linked to enhanced tolerance. As plant epigenomic research progresses, its application in sustainable agriculture becomes increasingly evident offering environmentally friendly solutions to mitigate the impact of heavy metal pollution. This review provides a foundation for future research aimed at leveraging epigenetic tools to engineer crops capable of thriving under metal stress, thereby contributing to resilient agricultural systems and sustainable food production.

Drought poses a major threat to global food security, making it critical to understand the molecular mechanisms underlying plant responses to water scarcity. Epigenetic modifications, including DNA methylation and histone alterations, play central roles in regulating genes and hormonal pathways essential for drought adaptation. MicroRNAs, while primarily functioning as post-transcriptional regulators, can also influence epigenetic pathways and contribute to chromatin remodelling, suggesting a role in modulating epigenetic memory. Investigating these interactions is essential for understanding how plants integrate epigenetic and post-transcriptional regulation during stress. Epigenetic memory in drought-adapted plants provides insights into the transgenerational inheritance of adaptive traits and reveals how plants balance genome stability with flexibility. The crosstalk between epigenetic mechanisms and hormonal signalling is crucial for fine-tuning gene expression, promoting drought resilience. This review proposes a conceptual framework integrating epigenetic, hormonal, and miRNA-mediated regulation of drought responses. It emphasizes the impact of advanced technologies, such as bisulfite sequencing and CRISPR-Cas9, in dissecting plant epigenetic responses to drought. These approaches improve our understanding of drought tolerance mechanisms and offer promising strategies for developing resilient crops for sustainable agriculture. However, direct evidence linking epitranscriptomic modifications to long-term drought memory remains limited, and this emerging regulatory layer requires further experimental validation.

Allelopathy is an ecological process in which released chemicals modify the performance of neighbouring organisms, whereas phytotoxicity describes an inhibitory response to a substance under a defined assay and, by itself, does not demonstrate field-level allelopathy. This critical narrative review combines a structured re-screening of the literature with targeted updating through 21 August 2026. Searches used combinations of allelopath*, allelochemical*, phytotox*, bioherbicid*, hormesis, biostimulant*, rhizosphere, microbiome, formulation, resistance, and regulation; peer-reviewed studies were complemented by authoritative regulatory and resistance databases. Evidence was appraised according to experimental context and mechanistic strength, explicitly distinguishing field or whole-plant validation from controlled bioassays, experimentally supported molecular targets from physiological or omics associations, and computational predictions. The synthesis covers chemical diversity, botanical and microbial sources, agro-industrial by-products, mechanisms of phytotoxicity and low-dose responses, rhizosphere interactions, and formulation strategies. Important corrections emerge from this evidence hierarchy: strigolactones are carotenoid-derived apocarotenoid hormones/signals rather than sesquiterpenes; multi-target activity does not preclude resistance evolution; cyanobacterial responses cannot be directly extrapolated to weeds or crops; and hormetic stimulation under controlled conditions is not equivalent to reliable field biostimulant performance. The principal translational gaps are insufficient dose–response standardisation, limited crop-selectivity and field validation, variable biomass chemistry, incomplete carrier and non-target safety data, and regulatory uncertainty for multifunctional products. Allelochemicals therefore represent promising components of integrated crop protection, but their agronomic value depends on rigorous evidence, formulation-specific validation, and context-dependent deployment rather than on laboratory phytotoxicity alone.

The increasing incidence of herbicide-resistant weeds and concerns over synthetic herbicides are driving the search for natural alternatives. This study evaluated the post-emergence bioherbicidal activity and mode of action of Santolina chamaecyparissus L. essential oil against Bidens pilosa L. seedlings. Gas chromatography–mass spectrometry revealed a chemically complex oil dominated by oxygenated monoterpenes, including cuminic alcohol, cis-carveol, cis-pinocarveol, α-phellandrene, and limonene. A preliminary dose–response assay identified an ED₅₀ of 0.82% (v/v). At this concentration, visible injury reached 75.9% at 72 h, while leaf relative water content declined to 40.0%. Electrolyte leakage reached 77.6% at 24 h, accompanied by a threefold increase in malondialdehyde, indicating severe membrane damage and lipid peroxidation. Chlorophyll fluorescence imaging showed impaired photosystem II function, reduced electron transport, altered energy dissipation, and loss of photosynthetic vitality. Photosynthetic pigments declined after 24 h, with chlorophyll a reduced by approximately 32.5%. Untargeted metabolomics revealed time-dependent depletion of soluble sugars, organic acids, ascorbate, and shikimate, together with accumulation of proline, γ-aminobutyric acid, trehalose, and branched-chain amino acids. Network analysis indicated loss of metabolic coordination. Overall, under the controlled experimental conditions used here, S. chamaecyparissus essential oil exhibited a rapid contact-type phytotoxic action characterised by membrane disruption, oxidative damage, dehydration, photosynthetic impairment, and extensive metabolic perturbation.