With the expansion of saline-alkaline tolerant rice in China, the effects of salinity stress (NaCl) on quinclorac-resistant Echinochloa crus-galli (L.) Beauv (E. crus-galli) is unclear. In this study, the growth chamber experiment was conducted to test the germination and growth physiology of seven populations of E. crus-galli with quinclorac-different resistance levels which were collected from Hunan province. The results showed that a significant decrease of the germination rate and fresh weight of the plants, as well as the length of the roots and young shoots appeared, along with the increased resistance while treated with NaCl. However, no significant differences were detected between quinclorac-resistant and -susceptible E. crus-galli populations while without NaCl treatment. A further study with spectrophotometer showed that the salinity treatment resulted in the increase of the GST activity in all E. crus-galli populations, which are more obvious in those resistant biotypes, and transcriptomics revealed that salt stress reduces the adaptability of quinclorac-resistant E. crus-galli by reducing the biosynthesis, activities of antioxidant enzymes and metabolic enzyme. This study demonstrated that salinity stress (NaCl) may reduce the adaptability of quinclorac-resistant E. crus-galli.

Botanical compounds with herbicidal activity exhibit safety, low toxicity, and low chances of herbicide resistance development in plants. They have widespread applications in green agricultural production and the development of organic agriculture. In the present study, dihydrocoumarin showed potential as a botanical herbicide, and its phenotypic characteristics and mechanism of action were studied in barnyardgrass [Echinochloa crus-galli (L.) P.Beauv.] seedlings. The results indicated that dihydrocoumarin inhibited the growth of barnyardgrass without causing significant inhibition of rice seedling growth at concentrations ranging between 0.5 and 1.0 g/L. Additionally, dihydrocoumarin treatment could cause oxidative stress in barnyardgrass, disrupt the cell membrane, and reduce the root cell activity, resulting in root cell death. Transcriptomic analyses revealed that dihydrocoumarin could inhibit barnyardgrass normal growth by affecting the signal transduction of plant hormones. The results showed significant differential expression of plant hormone signal transduction genes in barnyardgrass. Additionally, dihydrocoumarin interfered with the expression of numerous phenylpropanoid biosynthesis genes in barnyardgrass that affect the production of various vital metabolites. We speculate that the barnyardgrass growth was suppressed by the interaction among hormones and phenylpropanoid biosynthesis genes, indicating that dihydrocoumarin can be applied as a bioherbicide to control barnyardgrass growth in rice transplanting fields.

S-metolachlor is a selective pre-emergence herbicide used in dryland. However, it is challenging to employ in paddy fields due to its phytotoxic effects on rice. As a common phytohormone, Gibberellin-3 (GA₃) is inferred to have the ability to alleviate herbicide phytotoxicity. This study first quantitatively verified the phytotoxicity of s-metolachlor to rice and then demonstrated the mitigative effect of GA₃ on these adverse reactions. Furthermore, a transcriptome of rice seedlings subjected to different treatments was constructed to assemble the reference genes, followed by comparative metabolomics and proteomics analyses. Metabolomics revealed an enrichment of flavonoid metabolites in the group of adding GA₃, and these flavonoids can eliminate ROS in plants. Proteomics analysis indicated that differential proteins were enriched in the phenylpropanoid biosynthesis pathway responsible for the synthesis of flavonoids and that the functions of most differential proteins are associated with peroxidase. The proteome, combined with the transcriptome, revealed that the expressions of proteins and genes was related to the POD activity in the group of adding GA₃. It was speculated that the elimination of ROS is key to alleviating the stress of s-metolachlor on rice growth. It was inferred that the mechanism of GA₃ in alleviating the phytotoxicity of the substance s-metolachlor is by increasing the activity of the POD and influencing the growth of rice seedlings through the restoration of flavonoid synthesis. In this study, we screened GA₃ as a safener to alleviate the phytotoxicity of s-metolachlor on rice. On this basis, the mechanism of alleviating phytotoxicity was studied. The application range of s-metolachlor might be expanded, providing a new supplementary method for weed control and herbicide resistance management.

Background Rice is one of the most important staple dietary constituents worldwide, so improving cultivated rice yields is crucial for global food security. Fulvic acid (FA) is a plant growth promoter and organic fertilizer, and investigating its effects on rice root growth is of great practical significance for improving rice yield and quality. Results This study examined the effects of different FA concentrations on the growth of rice seedlings. Low FA concentrations (0.05 g/L) promoted rice seedling growth, whereas high FA concentrations (0.5 g/L) inhibited root growth, reduced cell activity and enzyme activity in the root tip, and accumulated reactive oxygen species in root cells. To investigate the underlying molecular mechanisms, we performed transcriptomic analysis and found that auxin (Aux) may participate in FA-mediated growth. Furthermore, transcriptome heatmap analysis showed a significant upregulation of the Aux/indoleacetic acid (Aux/IAA) gene family after FA treatment, suggesting that this gene family plays an important role in the effects of FA on root growth. Moreover, changes in endogenous Aux content and addition of exogenous Aux inhibitors confirmed the involvement of FA in rice seedling root growth and in the synthesis and transduction pathway of Aux. Conclusions This study demonstrated that the effects of FA on rice root growth may be achieved through the Aux synthesis and transduction pathway. We constructed a transcriptome landscape of the Aux synthesis and transduction pathway in FA-treated rice and identified a possible candidate gene family, IAA/Aux. These findings provide valuable clues for further understanding the mechanisms underlying the effects of FA on root growth in rice seedlings and offer new insights into the development of strategies for enhancing rice production.

Invasive alien plants seriously threaten native plant biodiversity and agricultural production. The development of environmentally friendly agriculture requires sustainable weed control techniques to manage these invasive alien weeds. This study evaluated the allelopathic effects of ethanol extract from Artemisia frigida against five invasive alien plants (Ageratum conyzoides, Bidens pilosa, Ipomoea purpurea, Eclipta prostrata, and Amaranthus retroflexus). The main components in the extract were identified using high-performance liquid chromatography–tandem mass spectrometry (LC-MS/MS), and we assessed their allelopathic effects on seed germination of the five species. The results showed that the ethanol extract of A. frigida completely inhibited seed germination of all five invasive plants at 5 g·L⁻¹. Thirteen components were identified, among which 4-ethyloctanoic acid, cis-jasmone, and p-anisic acid exhibited significant inhibitory effects. Notably, 4-ethyloctanoic acid demonstrated broad-spectrum herbicidal activity. At 50 mg·L⁻¹, it completely inhibited B. pilosa growth and had the strongest inhibitory effects on A. conyzoides and E. prostrata. This compound disrupted redox homeostasis and induced oxidative stress by modulating antioxidant enzyme activities, including superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT). These findings indicate that 4-ethyloctanoic acid is the main allelochemical with herbicidal potential in A. frigida, providing a theoretical basis for developing novel herbicides and environmentally friendly control techniques for invasive alien plants.