Allelopathic effects of the extracts from an invasive species Solidago canadensis L. on Microcystis aeruginosa

Phenolic Profile and Antioxidant Capacity of Invasive Solidago canadensis L.: Potential Applications in Phytopharmacy

Canadian goldenrod (Solidago canadensis L.), an invasive plant in Europe, is known for its allelopathic activity and is rich in bioactive compounds like flavonoids and phenolic acids, with significant pharmacological potential. This study presents the LC-MS phenolic profiles of leaf and flower extracts from S. canadensis, an invasive alien plant in the Istria region (Croatia). Total phenolics (TP) (45.78-110.68 mg GAE/g DW) and non-flavonoids (TNF) (28.38-72.20 mg GAE/g DW) were found to be more abundant in ethanolic than in methanolic extracts. The antioxidant capacity (AC), as measured by ABTS, DPPH, and FRAP assays, was higher in flower extracts compared to leaf extracts. A non-targeted metabolomics approach was used, and 41 phenolic compounds in leaves and 36 in flowers were identified, with hydroxycinnamic acids and flavonols being the most abundant. 5-caffeoylquinic acid was quantitatively predominant in the leaf extracts, while quercetin-3-rutinoside dominated the flower extracts. Five leaf-specific compounds were identified (dicaffeoylquinic acid 2, 4-p-coumaroylquinic acid 1, p-hydroxybenzoic acid, quercetin-3-rhamnoside, and quercetin acetylhexoside 1), suggesting targeted extraction for different pharmacological applications. This study highlights the therapeutic potential of S. canadensis and underscores the need for further research on the bioavailability, efficacy, and safety of its compounds, potentially transforming this ecological threat into a valuable resource for drug development.

The Invasive Alien Plant Solidago canadensis: Phytochemical Composition, Ecosystem Service Potential, and Application in Bioeconomy

Solidago canadensis L. (Canadian goldenrod) is a widely distributed invasive herb from the Asteraceae family. It contains compounds that can change the soil structure and its nutritional components and thus affect indigenous species' growth, germination, and survival. Consequently, it can pose a major ecological threat to biodiversity. On the other hand, many studies show that this species, due to its chemical properties, can be used for many positive purposes in pharmacy, agriculture, medicine, cosmetic industry, etc. S. canadensis contains a diverse array of bioactive compounds that may be responsible for antioxidant, antimicrobial, and anticancer activities. Many studies have discussed the invasiveness of S. canadensis, and several chemical and genetic differences between this plant in native and introduced environments have been discovered. Previous ecological and environmental evaluations of the potential of S. canadensis as an ecosystem services provider have come out with four promising groups of its products: active extracts, essential oil, fuel, and others. Although identified, there is a need for detailed validation and prioritisation of ecosystem services. This article aims to overview the S. canadensis invasive features, emphasising chemical characterisation and its potential for providing ecosystem services. Moreover, it identifies scenarios and proposes a methodology for estimating S. canadensis use in bioeconomy.

Dosage impact of submerged plants extracts on Microcystis aeruginosa growth: From hormesis to inhibition

Allelopathy has been demonstrated to be an environmentally friendly way to control harmful algal blooms. Allelochemicals of submerged plants have attracted extensive research due to their bioavailability. The dose-response of submerged plant extracts on algae growth is worth further study to improve the efficiency of bioremediation. In this study, the ultrasonic-enzymatic assistance method was utilized to extract allelochemicals from Ceratophyllum, Myriophyllum spicatum, and Vallisneria. The effects of low-dosage and high-dosage extracts on the growth of Microcystis aeruginosa were compared based on cell biomass and morphology, photosynthetic parameters, reactive oxygen species (ROS), superoxide dismutase (SOD), catalase (CAT), and malondialdehyde (MDA) levels. The results showed that the three submerged plant extracts exhibited hormetic effects at low dosages and inhibitory effects at high dosages on algal growth. Within 48 h of cultivation, the enzymatic activities of Microcystis aeruginosa fluctuated, suggesting that the extracts of the three submerged plants induced different oxidative reactions. After 120 h of cultivation with high-dosage extracts, the physiological and biochemical reactions of Microcystis aeruginosa significantly decreased, indicating the effectiveness of the allelopathy of Ceratophyllum, Myriophyllum spicatum, and Vallisneria extracts in controlling algal blooms. The phenomenon of hormesis and inhibition effect confirmed a significant dose-response relationship between the allelochemicals of submerged plant extracts and Microcystis aeruginosa, which could be attributed to the composition and content of allelochemicals. These findings highlight the importance of the relative concentration of the biological algaecide and will benefit other researchers in determining the safe dosage of plant allelochemicals when used in water.

Effects of dissolved organic matter from sediment and soil samples on the growth and physiology of four bloom-forming algal species

Algal blooms negatively impact the water quality of reservoirs; however, the role of dissolved organic matter (DOM) in bloom formation in reservoirs has not been investigated. Therefore, we assessed the compositions of sediment- and soil-derived DOM and their effects on the growth, physiology, and photosynthetic activity of Microcystis aeruginosa, Anabaena sp., Chlamydomonas sp., and Peridiniopsis sp. (bloom-forming species). Sediment DOM promoted the growth of all algal species, whereas soil DOM significantly promoted the growth of Chlamydomonas sp. and Peridiniopsis sp.; this effect was due to enhanced stress tolerance and photosynthetic efficiency exhibited by these algae under DOM treatment. However, soil DOM slightly inhibited the growth of Anabaena sp. by increasing reactive oxygen species levels and inactivating some photosystem II reaction centers. The tyrosine-like substance, humic acid-like substances, and unsaturated aliphatic compounds were the main DOM components that affected algal growth. The findings of this study will provide a theoretical foundation for the development of bloom-prevention strategies for river-type reservoirs.

Mechanistic insight into the inhibitory effect of artemisinin sustained-release inhibitors with different particle sizes on Microcystis aeruginosa

Environment-friendly algaecides based on allelopathy have been widely used to control harmful algal blooms. In this research, micro and nano scale artemisinin sustained-release algal inhibitor was prepared, the optimal preparation conditions were explored, and the inhibitory mechanism of artemisinin algaecides was turned perfect. The results showed that when the particle size of artemisinin sustained-release microspheres (ASMs) was 2/10,000 of artemisinin sustained-release granules (ASGs), the inhibitory effect was more remarkable. The optimal concentration of ASMs was 0.2 g L^-1, and the inhibitory effect reached 99% on the 10th day. The algal density and chlorophyll a both showed a downward trend, indicating that ASGs and ASMs could promote the degradation of chlorophyll a. The inhibition rate of ASGs was faster than that of ASMs on the 4th day, and the inhibitory effect of ASMs was more significant after the 5th day. The activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) increased rapidly at first and then decreased, which indicated that ASGs and ASMs caused oxidative damage to Microcystis aeruginosa and inhibited the activity of antioxidant enzymes. Furthermore, the content of the oxygen free radical (O^2-) and malondialdehyde (MDA) continued to rise after the 5th day, and the protein, nucleic acid, and conductivity in the culture medium increased. These results showed that lipid peroxidation occurred in the algal cell membrane, and the permeability of the membrane increased. In summary, the ASMs had a significant sustained inhibitory effect while the ASGs had a better short-term effect. The main inhibitory mechanism of artemisinin algaecides is the irreversible damage of cell membrane.

Survey of the Solidago canadensis L. Morphological Traits and Essential Oil Production: Aboveground Biomass Growth and Abundance of the Invasive Goldenrod Appears to Be Reciprocally Enhanced within the Invaded Stands

Canadian goldenrod is one of the most widespread invasive neophytes in Europe with proven ecological and environmental consequences for the invaded plots. The morphological traits and productive features survey can offer a better insight view into the S. canadensis population ecology and the dynamic of its aboveground biomass growth. Equally, it can serve as a foundation for a balanced management proposal, with the aim of keeping an acceptable degree of Canadian goldenrod invasion. In the study, 600 specimens, collected at various phenological phases, from the twelve sampling stands in the eastern Slovakia, were processed. The obtained data were related to the degree of invasion, pH, soil moisture, overall stand area, and measure of interventions. Plants from the stands with a mild degree of goldenrod invasion (<50%), lower pH, and higher stand area were significantly lower and lighter; had a significantly lower number and weight of leaves; significantly shorter and lighter stems, in comparison to the plants from the stands with a heavy degree of invasion (>50%); a higher pH; and a smaller area. These plants also showed smaller essential oil productivity rate, and they achieved the growth peak a significantly later. Conversely, as the stand area decreased, and the S. canadensis % representation and soil reaction increased, goldenrods became significantly taller and heavier, with a higher number of leaves and a higher essential oil productivity rate. Canadian goldenrod shows, somewhat, a cyclical, self-growth-reinforcing feedback: the consecutive increase of the goldenrod’s aboveground biomass leads to an increase of its relative % abundance within the invaded stands. Consequently, the increase of the goldenrod’s relative % abundance leads to the plants aboveground biomass consecutive growth, and so on.

PLDα1 and GPA1 are involved in the stomatal closure induced by Oridonin in Arabidopsis thaliana

Oridonin is an important diterpenoid, which plays an important role in plant growth and development. PLDα1 and GPA1 are involved in many biotic or abiotic stresses. In this study, using the seedlings of Arabidopsis thaliana L. wild type (WT), PLDα1 defective mutant (pldα1), GPA1 defective mutant (gpa1) and pldα1/gpa1 double mutant as materials, the effect of stomatal apertures responding to Oridonin and the functions of PLDα1 and GPA1 in this response were investigated. The results showed that 60 μmol·L-1 of Oridonin induced stomatal closure and significantly increased the relative expression levels of GPA1 and PLDα1. Oridonin increased H2O2 accumulation in guard cells by inhibiting the antioxidant enzymes. The increase of H2O2 caused the expression of OST1, which is a positive regulatory gene for stomatal closure. Both PLDα1 and GPA1 were involved in Oridonin-induced stomatal closure and PLDα1 acted downstream of GPA1. The results suggested that Oridonin caused stomatal closure by affecting GPA1 and promoting PLDα1 to produce PA, and further accumulating H2O2 to upregulate gene OST1.

A review on control of harmful algal blooms by plant-derived allelochemicals

Harmful algal blooms (HABs) have several negative impacts on aquatic ecosystem, and even harm to humans. Utilization of allelochemicals to inhibit microalgal overgrowth is an environment-friendly approach for controlling HABs. This paper demonstrated the development of allelochemicals with algicidal effects, including the development history of allelopathy, the application methods, the reported allelopathic plants and their derived allelochemicals. Allelopathy is a promising strategy to control HABs as the effectiveness of allelochemicals on inhibiting microalgae cells has been discovered and confirmed for many years. The proposed allelopathic mechanisms and species-selective properties were expounded as well. Moreover, this paper further proposed suggestions for the further research and development of allelopathy strategy for HABs control.

Antimicrobial Activity and Chemical Composition of Essential Oil Extracted from Solidago canadensis L. Growing Wild in Slovakia

Plant essential oils (EOs) are one of the most relevant natural products due to their biological, medicinal, and nutritional properties. The promising biological effects of many plants EOs encourage researchers to study their biochemical properties to be used as possible natural alternatives for commercial pesticides and not only as herbal medicines. The current research has been conducted to study the microbicide effect of Solidago canadensis L. EO to control some common plant diseases caused by several postharvest phytopathogenic fungi (Monilinia fructicola, Botrytis cinerea, Aspergillus niger, and Penicillium expansum) in comparison with Azoxystrobin as a large spectrum fungicide. The antibacterial activity has been carried out against some phytopathogenic bacteria (Bacillus megaterium and Clavibacter michiganensis (G+ve) and Xanthomonas campestris, Pseudomonas fluorescens, and Pseudomonas syringae pv. phaseolicola (G−ve)) compared to the synthetic antibiotic Tetracycline. Minimum inhibitory concentration was carried out to determine the lowest effective EO dose using a 96-well microplate. The cell membrane permeability was also evaluated by measuring the electric conductivity (EC) to examine the possible mechanisms of action of S. canadensis EO. Chemical characterization of EO has been carried out using gas chromatography and mass spectrometry (GC-MS). Thirty-two identified components in S. canadensis EO presented 97.7% of total compounds in EO. The principal compounds were identified as germacrene D (34.9%), limonene (12.5%), α-pinene (11.6%), β-elemene (7.1%), and bornyl acetate (6.3%). In addition, S. canadensis EO demonstrated promising in vitro antimicrobial activities against the majority of tested phytopathogens at all tested concentrations.

Allelopathic Effects of Aqueous Leaf Extracts from Four Shrub Species on Seed Germination and Initial Growth of Amygdalus pedunculata Pall

This study aimed to screen out the shrub species which can promote the seed germination and seedling growth of Amygdalus pedunculata Pall. and offer insight for ecological environment governance of the coal mines subsidence area in Mu Us Sandy Land, Yulin City of Shaanxi Province. The indoor bioassay method was used to study the aqueous leaf extracts from Amorpha fruticosa Linn., Hedysarum mongolicum Turez., Sabina vulgaris Ant., and Hippophae rhamnoides Linn. under different concentration gradients to examine seed germination, initial growth, and physiological and biochemical of two Amygdalus pedunculata varieties (YY-1 from Yuyang County (YY) and SM-6 from Shenmu County (SM), Shaanxi Province, China). The results showed that with aqueous leaf extracts concentrations at lower concentrations of 0.025 (T1) and 0.05 g·mL−1 (T2) from A. fruticosa, H. mongolicum, and S. vulgaris significantly promoted seed germination and seedling growth of two A. pedunculata varieties. Moreover, H. rhamnoides aqueous leaf extracts had the strongest inhibitory effect on seed germination and seedling growth of A. pedunculata, and death occurred at concentrations of 0.15 (T4) and 0.20 g·mL−1 (T5). The enzyme activity and chlorophyll content of the A. pedunculata leaves decreased with an increase in the aqueous leaf extracts concentration of the four shrubs; the change trend of malondialdehyde content was the opposite. Root activity of the A. pedunculata increased and then decreased. The H. mongolicum and S. vulgaris are the most suitable mixed tree species for YY-1, while H. mongolicum and A. fruticosa are the most suitable mixed tree species for SM-6 at a relatively low density with more security. The results provide a theoretical basis and technical support for the establishment of an artificial mixed forest of A. pedunculata in the coal mine subsidence area of Mu Us Sandy Land.

The algicidal mechanism of prodigiosin from Hahella sp. KA22 against Microcystis aeruginosa

In recent years, Microcystis aeruginosa blooms have occurred throughout the world, causing huge economic losses and destroying aquatic ecosystems. It is necessary to develop effective and ecofriendly methods to control M. aeruginosa blooms. Here, we report a high algicidal activity of prodigiosin (PG) against M. aeruginosa as well as the algicidal mechanism. PG showed high algicidal activity against M. aeruginosa, with a 50% lethal dose (LD₅₀) of 5.87 μg/mL in 72 h. A combination of methods, including propidium iodide and Annexin V-fluorescein staining assays and light and electron microscopy indicated the existence of two modes of cell death with features similar to those in eukaryotic programmed cell death: necrotic-like and apoptotic-like. Biochemical and physiological analyses showed that PG generates reactive oxygen species (ROS), which induce lipid peroxidation, damage the membrane system and destroy the function of the photosystem. A proteomics analysis revealed that many proteins were differentially expressed in response to PG stress and that most of these proteins were involved in important metabolic processes, which may trigger necrotic-like or apoptotic-like cell death. The present study sheds light on the multiple toxicity mechanisms of PG on M. aeruginosa and its potential for controlling the occurrence of M. aeruginosa blooms in lakes.

Allelopathic Effects, Physiological Responses and Phenolic Compounds in Litter Extracts of Juniperus rigidaSieb. et Zucc

The allelopathic effects of Juniperus rigida litter aqueous extract (LE) on wheat and Pinus tabuliformis were studied, as well as the physiological responses to the extract. High concentration LE (0.10 g Dw/ml) significantly inhibited the seed germination and seedling growth in receptor plants. The chlorophyll content and root activity in the wheat seedlings were reduced significantly across all treatments; however, those were more prominently reduced at high concentration (0.10 g Dw/ml) but received little stimulation at low concentration (0.025 g Dw/ml) in P. tabuliformis. The content of malonaldehyde (MDA) increased with increasing concentrations of LE, except at 0.025 g Dw/ml. Activities of antioxidant enzymes (POD, CAT and SOD) in receptor plants were all significantly inhibited at high concentrations but stimulated at low concentrations. These results demonstrate that the aqueous extract from J. rigida litter has allelopathic potential. Various phenolic compounds were identified in litter aqueous extract and litter ethanol extract by HPLC. The phenolic compound content in the aqueous extract was significantly lower than that in the ethanol extract. Chlorogenic acid and podophyllotoxin were the predominant phenolic compounds in both types of litter extracts. These findings suggest that the seed germination and seedling growth of P. tabuliformis and wheat would be inhibited when planted near large amounts J. rigida litter.

Solidago canadensis L. Essential Oil Vapor Effectively Inhibits Botrytis cinerea Growth and Preserves Postharvest Quality of Strawberry as a Food Model System

This study investigated the anti-fungal properties of Solidago canadensis L. essential oil (SCLEO) against Botrytis cinerea in vitro, and its ability to control gray mold and maintain quality in strawberry fruits. SCLEO exhibited dose-dependent antifungal activity against B. cinerea and profoundly altered mycelial morphology, cellular ultrastructure, and membrane permeability as evaluated by scanning electron microscopy, transmission electron microscopy, and fluorescence microscopy. SCLEO vapor at 0.1 mL/L maintained higher sensory acceptance and reduced decay of fresh strawberry fruit, and also reduced gray mold in artificially inoculated fruit. SCLEO treatment did not, however, stimulate phenylalanin ammonia-lyase, polyphenol oxidase, or chitinase, enzymes related to disease resistance. This suggests that SCLEO reduces gray mold by direct inhibition of pathogen growth. SCLEO vapor may provide a new and effective strategy for controlling postharvest disease and maintaining quality in strawberries.

Inhibitory mechanisms of Acacia mearnsii extracts on the growth of Microcystis aeruginosa

Our previous work revealed that Acacia mearnsii extract can inhibit the growth of Microcystis aeruginosa, the common species forming toxic cyanobacterial blooms in eutrophic freshwater. In the present study, we demonstrated that this plant extract can significantly increase cell membrane permeability and Ca²⁺/Mg²⁺-ATPase activity on the membrane. Long-term exposure to concentrations of 20 ppm A. mearnsii extract led to algal cell membrane leakage or even lysis. Comparison of expression of three photosynthesis-related genes (rbcL, psaB and psbD) in M. aeruginosa with and without plant extract treatment revealed that their expression was remarkably reduced in the presence of the extract. Down-regulation of photosynthesis-related genes could indicate the inhibition of the photosynthetic process. Thus, our results suggested that both photosynthetic systems and membranes of M. aeruginosa are potentially damaged by A. mearnsii extract.