Many specialized metabolites found in plants have significant potential for developing environmentally friendly weed management solutions. This review focuses on the phytotoxic effects of volatile terpenes and phenolic compounds, particularly nepetalactone, an iridoid monoterpenoid from Nepeta species, and phloretin, a dihydrochalcone predominantly found in the genus Malus. We highlight current findings on their herbicidal effects, including morphological, physiological, and biochemical responses in target plants. These results underscore their potential for developing sustainable herbicides that could control weeds with minimal environmental impact. We also discuss their soil persistence and methods to enhance their solubility, chemical stability, and bioavailability. Additionally, the possible effects on non-target organisms, such as pollinators, non-pollinating insects, and soil microbiota, are considered. However, further research and a deeper understanding of their long-term ecological impact, along with a resistance development risk assessment, is essential for the potential development of bioherbicides that could be applied in sustainable weed management practices.

Flower color is an important characteristic that determines the commercial value of ornamental plants. The development of modern biotechnology methods such as genetic engineering enables the creation of new flower colors that cannot be achieved with classical methods of hybridization or mutational breeding. This is the first report on the successful Agrobacterium-mediated genetic transformation of Viola cornuta L. The hypocotyl explants of cv. “Lutea Splendens” variety with yellow flowers were transformed with A. tumefaciens carrying empty pWBVec10a vector (Llccs⁻) or pWBVec10a/CaMV 35S::Llccs::TNos vector (Llccs⁺) for capsanthin/capsorubin synthase gene (Llccs) from tiger lily (Lilium lancifolium). A comparative study of shoot multiplication, rooting ability during culture in vitro, as well as phenotypic characteristics of untransformed (control) and transgenic Llccs⁻ and Llccs⁺ plants during ex vitro growth and flowering is presented. Successful integration of Llccs transgene allows the synthesis of red pigment capsanthin in petal cells that gives flowers different shades of an orange/reddish color. We demonstrate that the ectopic expression of Llccs gene in ornamental plants, such as V. cornuta “Lutea Splendens” could successfully be used to change flower color from yellow to different shades of orange.

The present study evaluates the phytotoxic effects of phloretin, a prevalent secondary metabolite of apple trees, on the broadleaf weed Capsella bursa-pastoris (L.) Medik. known for its resistant myxospermous seeds that form a long-lasting soil bank. The results indicate a significant, dose-dependent inhibitory effect of phloretin on the growth and morphological parameters of weed seedlings grown in vitro. Although the applied phloretin concentrations (250–1000 µM) were not lethal to the C. bursa-pastoris seedlings after two weeks, the metabolism of the seedlings was impaired, resulting in an accumulation of lipid droplets in the root tips and root hairs. Histochemical analysis shows deposits of phenols in the root epidermal cells, which are probably aggregates of phloretin or its metabolic derivatives. The accumulation of pectin in the cell walls of root border cells in phloretin-treated seedlings indicates an attempt to reduce the uptake of phloretin and reduce its concentration in the cells. Inhibition of shoot growth associated with chlorosis and reduced photosynthetic pigment content is a consequence of seedling exposure to phloretin. This study provides a basis for further evaluation of phloretin as a new bioherbicidal compound and for elucidating the mechanism underlying its phytotoxic activity.

Phloretin is a naturally occurring dihydrochalcone, predominantly found in apple species (Malus spp.), that has recently attracted attention as a phytotoxic allelochemical with potential for bioherbicide development. However, the contribution of oxidative stress to its phytotoxic effects remains unclear and appears to be species-dependent. We investigated the involvement of oxidative stress in phloretin-induced phytotoxicity in Capsella bursa-pastoris (L.) Medik. by assessing oxidative stress markers alongside enzymatic and non-enzymatic antioxidant responses. A two-week exposure to 500 μM phloretin significantly increased total phenolic content and ABTS radical scavenging capacity. Total superoxide dismutase (SOD) activity increased, accompanied by enhanced Mn-SOD band intensity, indicating an intensified mitochondrial antioxidant response. In contrast, catalase (CAT) activity decreased, whereas peroxidase (POX) activity remained unchanged. The increased SOD activity, without a corresponding increase in H₂O₂-scavenging enzymes, was accompanied by elevated malondialdehyde (MDA) and proline levels, suggesting that the antioxidant response was insufficient to restore cellular redox homeostasis and prevent oxidative damage. Overall, our findings demonstrate that phloretin treatment leads to a redox imbalance accompanied by increased lipid peroxidation despite activation of antioxidant defenses, identifying oxidative stress as an important, species-dependent component of its phytotoxicity.