Nepetalactone-rich essential oil mitigates phosphinothricin-induced ammonium toxicity in Arabidopsis thaliana (L.) Heynh

Via Air or Rhizosphere: The Phytotoxicity of Nepeta Essential Oils and Malus Dihydrochalcones

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.

Antagonistic Interaction between Phosphinothricin and Nepeta rtanjensis Essential Oil Affected Ammonium Metabolism and Antioxidant Defense of Arabidopsis Grown In Vitro

Phosphinothricin (PPT) is one of the most widely used herbicides. PTT targets glutamine synthetase (GS) activity in plants, and its phytotoxicity is ascribed to ammonium accumulation and reactive oxygen species bursts, which drives rapid lipid peroxidation of cell membranes. In agricultural fields, PPT is extensively sprayed on plant foliage; however, a portion of the herbicide reaches the soil. According to the present study, PPT absorbed via roots can be phytotoxic to Arabidopsis, inducing more adverse effects in roots than in shoots. Alterations in plant physiology caused by 10 days exposure to herbicide via roots are reflected through growth suppression, reduced chlorophyll content, perturbations in the sugar and organic acid metabolism, modifications in the activities and abundances of GS, catalase, peroxidase, and superoxide dismutase. Antagonistic interaction of Nepeta rtanjensis essential oil (NrEO) and PPT, emphasizes the existence of complex control mechanisms at the transcriptional and posttranslational level, which result in the mitigation of PPT-induced ammonium toxicity and in providing more efficient antioxidant defense of plants. Simultaneous application of the two agents in the field cannot be recommended; however, NrEO might be considered as the PPT post-treatment for reducing harmful effects of herbicide residues in the soil on non-target plants.

Alterations in nepetalactone metabolism during polyethylene glycol (PEG)-induced dehydration stress in two Nepeta species

A number of Nepeta species (fam. Lamiaceae) are interesting medicinal crops for arid and semi-arid areas, due to their ability to maintain essential developmental and physiological processes and to rationalize their specialized metabolism under water deficit growth conditions. The present research is, to our knowledge, the first attempt to investigate the molecular background of the dehydration-induced changes in specialized metabolism of Nepeta species, which will help to understand relations between dehydration stress on one hand and biomass production and yield of nepetalactone (NL) on the other. During the 6 days exposure of Nepeta rtanjensis Diklić & Milojević and Nepeta argolica Bory & Chaub. ssp. argolica plants to PEG-induced dehydration stress under experimental in vitro conditions, decrease in transcript levels of the majority of 10 NL biosynthetic genes, and some of the 5 transcription factors (TFs) were recorded, simultaneously with the initial reduction in NL content. The two model species evidently employ similar strategies in response to severe dehydration stress; however N. rtanjensis is highlighted as the species more efficient in maintaining NL amounts in tissues. The results suggest trichome-specific and co-ordinately regulated NL biosynthesis at the level of gene expression, with trichome enriched MYC2 and YABBY5 TFs being the potential positive regulators. Manipulation of such TFs can be effective for engineering the NL biosynthetic pathway, and for the increased production of cis,trans-NL in N. argolica ssp. argolica and trans,cis-NL in N. rtanjensis.