Artemisia argyi allelopathy: a generalist compromises hormone balance, element absorption, and photosynthesis of receptor plants

Elucidating the Underlying Allelopathy Effects of Euphorbia jolkinii on Arundinella hookeri Using Metabolomics Profiling

Euphorbia jolkinii dominates the subalpine meadows in Shangri-La (Southwest China) owing to its potent allelopathic effects. However, the effects underlying its allelopathy require further characterization at the physiological and molecular levels. In this study, the physiological, biochemical, and metabolic mechanisms underlying E. jolkinii allelopathy were investigated using Arundinella hookeri as a receptor plant. The treatment of A. hookeri seedlings with E. jolkinii aqueous extract (EJAE) disrupted their growth by inhibiting photosynthesis, disrupting oxidation systems, and increasing soluble sugar accumulation and chlorophyll synthesis. Collectively, this causes severe impairment accompanied by abnormal photosynthesis and reduced biomass accumulation. Moreover, EJAE treatment suppressed gibberellin, indoleacetic acid, zeatin, salicylic acid, and jasmonic acid levels while promoting abscisic acid accumulation. Further metabolomic analyses identified numerous differentially abundant metabolites primarily enriched in the α-linolenic, phenylpropanoid, and flavonoid biosynthesis pathways in EJAE-treated A. hookeri seedlings. This study demonstrated that E. jolkinii exhibits potent and comprehensive allelopathic effects on receptor plants, including a significant disruption of endogenous hormone synthesis, the inhibition of photosynthesis, an impairment of membrane and oxidation systems, and changes in crucial metabolic processes associated with α-linolenic, phenylpropanoid, and flavonoid biosynthesis. Thus, our study provides a solid theoretical foundation for understanding the regulatory mechanisms underlying E. jolkinii allelopathy.

Advances of the mechanism for copper tolerance in plants

Copper (Cu) is a vital trace element necessary for plants growth and development. It acts as a co-factor for enzymes and plays a crucial role in various physiological processes, including photosynthesis, respiration, antioxidant systems, and hormone signaling transduction. However, excessive amounts of Cu can disrupt normal physiological metabolism, thus hindering plant growth, development, and reducing yield. In recent years, the widespread abuse of Cu-containing fungicides and industrial Cu pollution has resulted in significant soil contamination. Therefore, it is of utmost importance to uncover the adverse effects of excessive Cu on plant growth and delve into the molecular mechanisms employed by plants to counteract the stress caused by excessive Cu. Recent studies have confirmed the inhibitory effects of excess Cu on mineral nutrition, chlorophyll biosynthesis, and antioxidant enzyme activity. This review systematically outlines the ways in which plants tolerate excessive Cu stress and summarizes them into eight Cu-tolerance strategies. Furthermore, it highlights the necessity for further research to comprehend the molecular regulatory mechanisms underlying the responses to excessive Cu stress.

Artemisia argyi leaf powder improves soil properties and recruits Sphingobium bacteria to promote the growth and yield of Pinellia ternata

Recent research has reported the strong herbicidal activity of Artemisia argyi leaf powder (AALP), indicating its high potential for use as an environmentally friendly weed management solution for ecological agriculture. However, AALP's impacts on soil physicochemical properties and microbial communities have remained uninvestigated. This study explores these effects through pot experiments assessing the AALP's efficacy in weed suppression and its ability to promote the growth of Pinellia ternata, a plant utilized in traditional Chinese medicine. The results demonstrate that a 10% concentration of AALP suppressed nearly 100% of all weeds. Additionally, AALP treatments at 2.5%, 5%, 7.5%, and 10% concentrations increased P. ternata yields by 29.79%, 24.76%, 35.67%, and 31.00%, respectively. A soil analysis revealed that AALP enhanced soil fertility by increasing the contents of nutrients such as SOM, AN, AP, AK, Ca, Fe, Mn, and Zn, as well as the enzyme activity of CAT, ACP, UE, and SC, creating an optimal growth environment for P. ternata. In addition, AALP significantly increased the PA (phenolic acid) content in soil, which is a key factor in inhibiting weed germination and growth. Furthermore, a microbial community structure analysis indicated an enrichment of Actinobacteriota and Bacteroidota after AALP treatment, with notable increases in the growth-promoting bacteria Sphingobium and Flavobacterium. A permutational multivariate analysis of variance (PERMANOVA) based on the Bray-Curtis distance reaveled that all of the tested soil properties were significantly correlated with changes in bacterial community composition except for pH. Further two-factor correlation network analysis identified AN, Zn, SC, and PA as key environmental factors. Finally, the Sphingobium sp. strain AFR15, isolated from AALP-treated soil, exhibited significant growth-promoting effects on P. ternata. After inoculation with Sphingobium sp. strain AFR15 for one month, the heights of P. ternata were increased significantly. The leaf length and leaf width of P. ternata were also positively correlated with the treatment concentration of AFR15, and the chlorophyll contents of the leaves also increased. This results highlighted Sphingobium sp. strain AFR15's potential as a specialized microbial fertilizer in crop yield increased. In conclusion, AALP applications not only control weeds but also promote P. ternata growth by improving soil physiochemical properties and fostering beneficial bacterial allies. These findings lay the groundwork for future research and promote the use of AALP in ecological agriculture.

Effects of Phloretin on Seedling Growth and Histochemical Distribution of Phenols, Polysaccharides and Lipids in Capsella bursa-pastoris (L.) Medik

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.

Artemisia arborescens (Vaill.) L.: Micromorphology, Essential Oil Composition, and Its Potential as an Alternative Biocontrol Product

Artemisia arborescens is a Mediterranean evergreen shrub, with silver grey-green tomentose leaves and a strong scent. It has various ethnopharmacological uses and its secondary metabolites have demonstrated antimicrobial, antiviral, pharmaceutical, phytotoxic, and insecticidal activities. Different extracts obtained from aerial parts of this species are known for their allelopathic effect, but similar studies on its essential oil (EO) are lacking. Therefore, we carried out a pharmacognostic study, obtaining the characterization of the secretory structures and the EO produced. Trans-thujone and camphor are the main components, followed by aromadendrene, camphene, and 8-cedren-13-ol. EO phytotoxic activity was tested on weed plants (Lolium multiflorum Lam. and Sinapis arvensis L.) and crops (Raphanus sativus L. and Cucumis sativus L.), showing inhibition on both germination and radical growth of the two weeds tested. The effects of the EO against the bacterial plant pathogens Xanthomonas campestris pv. campestris (Gram-) and Pseudomonas syringae pv. tomato (Gram+) was also assayed. The minimum inhibitory concentration (MIC) was observed when it was used undiluted [100% v/v], and growth inhibition when diluted at different doses. The antimicrobial activity was also confirmed by the cellular material release and biofilm formation assays. The overall data show that A. arborescens EO can find application as a potential alternative biocontrol product against weeds and plant pathogens. This goal is particularly important from the perspective of replacing synthetic pesticides with natural products, which safeguard both the environment and the health of consumers.

Changes of physiological characteristics, element accumulation and hormone metabolism of tea leaves in response to soil pH

Soil acidification is very likely to affect the growth of tea trees and reduce tea yield. In this study, we analyzed the effects of soils with different pH on the physiological characteristics of tea leaves and determined the multi-element content and hormone metabolomes of tea leaves by ICP-MS and LC-MS/MS, based on which we further analyzed their interaction. The results showed that increasing soil pH (3.29~5.32) was beneficial to increase the available nutrient content of the rhizosphere soil of tea tree, improve the antioxidant enzyme activity and photosynthesis capacity of tea tree leaves, and promote the growth of tea tree. Orthogonal partial least squares discriminant analysis (OPLS-DA) and bubble characteristics analysis were used to screen key elements and hormones for the effect of pH on tea leaves, which were further analyzed by redundancy analysis (RDA) and interaction network. The results showed that an increase in soil pH (3.29~5.32) favored the accumulation of seven key elements (C, K, Ca, Mg, Mn, P, S) in tea tree leaves, which in turn promoted the synthesis of six key hormones (salicylic acid, salicylic acid 2-O-β-glucoside, tryptamine, 2-oxindole-3-acetic acid, indole-3-acetic acid, trans-zeatin-O-glucoside). It can be seen that the increase in soil pH (3.29~5.32) enhanced the resistance of the tea tree itself, improved the photosynthesis ability of the tea tree, and effectively promoted the growth of the tea tree.

The Allelopathic Activity of Aqueous Extracts of Helianthus annuus L., Grown in Boreal Conditions, on Germination, Development, and Physiological Indices of Pisum sativum L

Evaluation of the allelopathy relationship between different crops is a sensible strategy fallowing the correct use of positive effects and to avoid the disadvantageous effects among plants. This study aimed to detect the allelopathic effect of aqueous extracts of sunflower (Helianthus annuus L.), grown in a boreal climatic zone, on the growth, subsequent development, and physiological traits of pea (Pisum sativum L.). Three factors have been studied: donor plant fertilization (unfertilized and fertilized), aqueous extracts from donor plant organs (leaves and stems (L+S), heads (H) and roots (R)); four concentrations of extracts (0%, 25%, 50% and 75%). The aqueous extracts from fertilized sunflower donor plant at 25% and 50% concentration acted as potential biostimulants that stimulated pea seed germination (SG), whereas L+S and R extracts at 75% concentration from unfertilized donor plant inhibited SG, at 4 days after sowing. The aqueous extracts demonstrated a stimulating effect on above-ground and root dry mass, compared to the control. The concentration of extracts demonstrated a significant inhibitory effect on SPAD. R extract revealed the strongest allelopathic effect on physiological traits of pea. L+S and H extracts at 25% concentration had stimulating effects, while 50% and 75% concentrations showed inhibiting effects on the photosynthetic rate. The water use efficiency, stomatal conductance, and stomatal limitation were inhibited, whereas, the transpiration rate, photosynthetic water use efficiency and intercellular CO₂ concentration were stimulated, with an increasing of extract concentrations, comparatively to the control.

Effects of Magnesium on Transcriptome and Physicochemical Index of Tea Leaves

Magnesium (Mg) is one of the essential elements for the growth of tea tree and is extremely important for its development. In this study, we investigated the effect of Mg on the transcriptome and physicochemical indexes of tea leaves, and the results showed that Mg could significantly affect the gene expression of tea leaves. The results of Orthogonal Partial Least-Squares Discriminant Analysis (OPLS-DA) model analysis showed that a total of 300 key genes (Variable Importance for the Projection, VIP > 1) were screened under different concentrations of Mg treatment, among which 140 genes were up-regulated and 160 genes were down-regulated. The bubble map was used to screen the characteristic genes from the above key genes, and a total of 121 representative characteristic genes were obtained, mainly involving 9 metabolic pathways. Among them, gene expression of three metabolic pathways, including porphyrin metabolism, alpha-linolenic acid metabolism and photosynthesis, showed an increasing trend with the increase of Mg concentration, while gene expression of four metabolic pathways, including biosynthesis of secondary metabolites, anthocyanin biosynthesis, ABC transporters, pentose and glucuronate interconversions, showed a decreasing trend. The results of physiological index analysis showed that with the increase of Mg concentration, the photosynthetic physiological index, theanine and soluble sugar content of tea leaves showed an increasing trend, while the content of tea polyphenol, flavone and caffeine showed a decreasing trend. The results of TOPSIS analysis showed that the physiological indexes of tea trees most affected by Mg were chlorophyll, tea polyphenols and flavonoids, while the metabolic pathways most affected by Mg on gene expression were the metabolic pathways and biosynthesis of secondary metabolites. It can be seen that the effects of Mg on tea tree were mainly related to photosynthesis and synthesis of secondary metabolites, and Mg was beneficial for improving the photosynthetic capacity of tea tree, enhancing the accumulation of primary metabolites, and thus increasing tea yield. However, Mg was not conducive to the synthesis of secondary metabolites of tea tree and the accumulation of main quality indexes of tea leaves.

Protective enzyme activity regulation in cotton (Gossypium hirsutum L.) in response to Scirpus planiculmis stress

Scirpus planiculmis, an important weed in rice and cotton fields, stresses crop growth and development, leading to yield loss. However, it is unclear how stressed plants respond to this weed. In this study, we analysed the stress effect of S. planiculmis on cotton under different weed densities, competition periods, and distribution conditions from the perspective of morphogenesis, physiological metabolism and crop yield. The effect of a low dose of herbicide on the relationship between cotton and S. planiculmis was also explored. The results showed that plant height, stem diameter, fresh weight, root length, boll number, single boll weight and yield of cotton all decreased with increasing S. planiculmis density and damage. The spatial distribution of S. planiculmis had no significant effect on plant height, stem diameter, fresh weight or root length of cotton, but crop yield loss decreased with increasing distance. S. planiculmis stress altered cotton chlorophyll, soluble protein and malondialdehyde (MDA) content, and protective enzyme activities. Compared with superoxide dismutase (SOD) and peroxidase (POD) activities, catalase (CAT) activity was increased under different S. planiculmis stress conditions. Therefore, we concluded that CAT plays a key role in protecting enzymes involved in defence responses. Under low-dose herbicide action, the activities of protective enzymes were increased, which helped cotton plants to resist S. planiculmis stress. The results revealed that regulating protective enzyme activities is important in cotton responses to S. planiculmis stress.