Allelopathic Potential Research Articles

Allelopathy of Root exuded of Two Sunflower Cultivars (Helianthus annuus L.) on weed companion

Two field experiments were conducted during 2015-2016 in Wasit province, Iraq to test the allelopathic potential of sunflower (Helianthus annuus .L). Two genotypes introduced to Iraq to screened allelopathic of root exuded against weeds in sunflower field. Two sunflower genotypes significantly inhibited total number and biomass of companion weeds and the inhibition is genotype dependent. Genotypes tested Asgria was the most allelopathic cultivars with the reduction in total weed number by 68.6% of control and weed biomass by 61.0% of the control respectively. Flamme was the less allelopathic genotypes comparted Asgria Genotypes , which inhibition in total weed number by 24% and weed biomass by 35.4% respectively of the control respectively. A staircase experiment indicated that root exudates of the Asgria cultivar suppressed weeds more than Flamme giving additional evidence for the superiority of the Asgria cultivar in its allelopathic weed suppression. Chemical analysis indicated the presence of phenols compound in root exudates of both cultivars with a significantly higher amount in the Asgria cultivar (0.403 mg/g) compared to cultivar Flamme( 0.220 mg/g ) and that total phenolic started to increase at 28 day then declined at end season. Chemical analysis on these phenolics by HPLC indicated the presence of several allelochemicals, viz, protocatechuic, , vanillic, syringic, , ferulic and p-coumaric acid.Chromatographic analyses indicated the presence phytotoxins in the root exudes of the tested sunflower genotypes. All the isolated compounds appeared to have different retention times and were identified as phenolic compounds

Trewia nudiflora Linn, a Medicinal Plant: Allelopathic Potential and Characterization of Bioactive Compounds from Its Leaf Extracts

Trewia nudiflora Linn. is a valuable forest resource due to its economic, ethnomedicinal, and ecological properties; however, its allelopathic potential is undocumented. Therefore, this research was designed to investigate the allelopathic impacts of T. nudiflora leaf extracts on alfalfa (Medicago sativa L.) and barnyard grass (Echinochloa crus-galli (L.) P. Beauv.) growth, as well as to isolate and to identify the active allelopathic substances responsible for these effects. A bioassay experiment with eight different treatments (0.1, 0.3, 1, 3, 10, 30, 100, and 300 mg dry weight (DW) equivalents of T. nudiflora extracts in mL−1) was carried out. The results showed that the growth of both plants decreased with increasing contents of T. nudiflora extracts, with the effect depending on the plant species and reaching its peak at a concentration of a 300 mg DW equivalent of T. nudiflora extract in mL−1. Active substances were isolated and identified using an HPLC system, which revealed the presences of methyl gallate and pinoresinol in aqueous methanol extracts of T. nudiflora. The shoot and root lengths of the alfalfa and the barnyard grass decreased significantly when they were treated with the methyl gallate and the pinoresinol. The allelopathic inhibition increased with increasing compound concentrations, with the root growth being more sensitive to the pinoresinol than to the methyl gallate, and it was significantly higher at the concentration of 10 mM. These results indicated that the T. nudiflora leaf extracts limited the growth of the treated plants, and the methyl gallate and pinoresinol in the extracts may have caused the inhibition of the T. nudiflora extracts. Thus, the leaf extracts of T. nudiflora and the substances methyl gallate and pinoresinol could be incorporated into sustainable agricultural practices or used to develop bioherbicides that would promote sustainable weed management practices.

Allelopathic Potential of Tropical Plants—A Review

The need to meet food demand becomes more urgent as it is forecasted to increase by 50% over the next century. Thus, agronomists promote sensible tools and approaches to eradicate factors that hamper crop production, mainly weeds. The constant use of chemical herbicides to control weeds leads to an increased risk of herbicide-resistant weed populations, environmental pollution, unsafe agricultural products, and negative effects on human health. These problems have caused an interest among researchers to replace synthetic herbicides with alternatives. The purpose of this review was to present the current knowledge base on allelopathic tropical plants and their potential for use in the development of natural product-based, environmentally friendly herbicides for sustainable agriculture, and to stimulate future discussion on this topic. The defence mechanisms of tropical plants have received particular attention because of their potential weed control ability as a natural pesticide that can prevent the overuse of synthetic pesticides. The ancient knowledge of the toxic properties of various tropical plants gives us a basis for creating a novel pest control approach. The synthesis of biopesticides based on allelochemicals opens up the possibility of utilizing natural compounds in crop protection and demonstrates the ability to deal with evolved pesticide resistance.

Assessment of Allelopathic Activity of Arachis pintoi Krapov. & W.C. Greg as a Potential Source of Natural Herbicide for Paddy Rice

Pinto peanut (Arachis pintoi Krapov. & W.C. Greg.) is an herbaceous perennial plant which belongs to the Leguminosae family. This plant is well known for its use as a cover crop, but little information is available on the allelopathic potential of this legume. Therefore, this study aimed to explore the allelopathic effects of A. pintoi under various screening conditions and to analyze its potential allelochemicals using gas chromatography–mass spectrometry (GC-MS). In laboratory bioassays, aqueous extracts of A. pintoi powder exerted the average inhibition of the growth of Echinochloa crus-galli (55.1%), Oryza sativa (77.1%), and Vigna radiata (60.1%), respectively, of which the root lengths of the tested plants were the most suppressed. In greenhouse experiments, E. crus-galli was inhibited by 63.4% at 200 g/m2 of A. pintoi dried powder application. In field trials, A. pintoi also significantly reduced the growth of E. crus-galli and natural weeds. By incorporating a dose of 200 g/m2, the average inhibition of E. crus-galli was 43.9%, the dry weight of natural paddy weeds was 43.1%, and rice yield was simultaneously increased by 35%. The growth inhibitions of weeds and tested plants were proportional to the doses of A. pintoi applied and varied with the tested plant species. Among three different solvent extracts (methanol, hexane, and ethyl acetate), the hexane extract exerted the highest suppression against the growth of E. crus-galli and L. sativa by IC50 against root and shoot growth = 4.08 and 8.4 mg/mL and 1.7 and 1.54 mg/mL, respectively, followed by ethyl acetate extract, while the least effective was methanol extract. From those extracts, a total of 35 substances were detected by GC-MS analyses, including 14 newly identified constituents, such as phenolic acids, stearic acid, palmitic acid, fatty acids, pyranones, and benzofurans, which may be responsible for the herbicidal effects of A. pintoi. This study suggests that A. pintoi may be used as a source of bioherbicide to minimize the dependency on harmful synthetic herbicides and enhance rice yield.

Insights into the chemical composition of Ocimum forskaolii and O. americanum essential oils and their phytotoxicity

The essential oils (EOs) of numerous Ocimum species are well-known. The EOs of O. forskaolii and O. americanum growing naturally in Saudi Arabia are compared chemically in the current study. The GC-MS and GC-FID analysis was used for identification and quantitation of EOs’ chemical components, and the chemometric analysis was used to determine the differences between the two species. Additionally, against the weeds Dactyloctenium aegyptium and Chenopodium murale, the allelopathic potentiality of the two EOs was assessed. Fifty-one compounds were assigned as overall O. forskaolii EO’ components, with abundance of mono- and sesquit-terpenes (40.49 and 55.15%, respectively). endo-Fenchol (18.15%), tau-cadinol (11.42%), β-atlantol (10.54%), α-eudesmol (7.29%), and α-terpineol (6.94%) were the major components. Sixty-one components were identified via the GC-MS analysis of O. americanum EO, with sesquiterpenes (81.24%) serving as the major class. α-Bulnesene (10.17%), germacrene B (7.72%), endo-borneol (5.51%), isoshyobunone (5.37%), and γ-eudesmol (5.31%) represented the main compounds. Chemometric study showed a distinct difference between the two species’ chemical make-up of the EOs, which might be attributed to genetic changes. The extracted EOs of O. forskaolii and O. americanum demonstrated a significant allelopathic effect against the weeds D. aegyptium and C. murale. Compared to O. americanum, O. forskaolii EO demonstrated greater allelopathic activity. The main components of each species may be a candidate for the observed allelopathic activity, which may act singularly or in combination.

Constituent content and allelopathic potential of eighteen extracts for the control of Urochloa decumbens under laboratory conditions

Invasive grasses, those of the genus Urochloa act aggressively, thereby inhibiting the germination and growth of native species. We investigated the allelopathic potential and constituent content of different plant species to determine their effect on the germination of Urochloa decumbens (Stapf) R.D. Webster. Eighteen (18) species from the families Anacardiaceae (1), Annonaceae (6), Euphorbiaceae (1), Fabaceae (2), Myrtaceae (1), Rubiaceae (4), Sapindaceae (2), and Tropaeolaceae (1) were selected to obtain methanolic extracts at 1% (m/v). The total phenols, flavonoids, condensed tannins, flavonols, and saponins were evaluated by colorimetric methods. To evaluate the allelopathic effect of methanolic extracts 25 seeds from U. decumbens were distributed in Petri dishes containing two sheets of germitest paper and 2 mL of extract, and they were maintained at 25 °C under white light. All methanolic extracts showed total phenols, flavonoids, flavonols, and condensed tannins; however, saponin was identified in A. coriacea, A. crassiflora, A. sylvatica, Psychotria carthagenensis, P. leiocarpa, and Tropaeolum majus. Annona dioica (Annonaceae), Stryphnodendron adstringens (Fabaceae), and Palicourea crocea (Rubiaceae) have allelopathic potential and showed decelerated U. decumbens seed germination and inhibited hypocotyl and radicle growth. These findings provide insights into alternative methods for controlling U. decumbens in areas of ecological restoration.

Phytochemical Screening and Allelopathic Potential of Important Medicinal Plants Used by Dhimal Community in Urlabari Municipality

A study was conducted to document the major ethnobotanicals used against different ailments from Dhimal community of Urlabari Municipality. Deductive research approach employed through household survey using semi-structured questionnaire with 115 respondents for research work. Out of 23 documented plants, Cuscuta reflexa Roxb., Mimosa pudica L. , Azadirachta indica A. Juss, Achyranthes aspera L. and Acorus calamus L. were screened for further phytochemical analysis based on fidelity level. Five treatments maintained as 3 different concentrations (5, 10, and 15% of stock solution), and control were arranged in a completely randomized design with three replications for evaluating allelopathic potential where selected botanical extracts on germination, radical, and plumule growth of wheat seedlings were examined under invitro condition. Mimosa pudica L. had the highest alkaloid (15.39%), Cuscuta reflexa Roxb. had the highest terpenoid (9.17%) and Acorus calamus L. had the highest saponin (5.49%) when calculated via gravimetric method. Germination, radical and plumule growth found under control treatment were 3.24ab±0.09, 2.94a ±0.09cm and 2.70a ±0.17cm respectively. The stock solution of Acorus calamus L. with 15% concentration extract resulted in the maximum reduction of radicle length (1.14e ±0.22cm) and plumule length (1.04h ±0.17cm), along with heavily controlled germination (1.05f ±0.17) of wheat seedlings. Thus, Acorus calamus L. proved the highest allelopathic potential on wheat seedling growth indicating further investigation on other crops.

Mechanisms involved in alien maples (Acer sp.) invasion process in the Central Europe. Testing hypotheses associated with species fitness

Maples (Acer sp.) are trees/shrubs of extraordinary aesthetic value, what favours them for wide utilisation in urban greenery. However, some of the non-native species became invasive in the new range and represent a threat to natural ecosystems. Therefore, after the definition of their frequency and planting history in Slovak cities and reinvestigation of ecological status, based on analysis of growth, reproduction biology, fruit dispersal, phenotypic plasticity and allelopathic potential, invasion hypotheses related to the species fitness were tested in non-invasive alien species, in respect of invasive box elder (A. negundo L.). Parks and residential areas from the socialistic era were dominated by silver maple (A. saccharinum L.) and private gardens by palm maple (A. palmatum Thunb.) cultivars. A shift to ´locally naturalised´ was confirmed in the former, and palm maple was taken into consideration in the alien flora list (as casual). The fastest growth was found in silver maple and box elder. The latter showed also extraordinary reproduction earliness, largest fruit production, flight range and seed viability. Specific leaf area mostly decreased in box elder towards summer, indicating its large phenotypic plasticity. However, the largest allelopathic effect was observed in silver maple. Hence, ´limiting similarity hypothesis´, ´ideal weed hypothesis´, ´propagule pressure hypothesis´ and ´phenotypic plasticity hypothesis´ were essential for box elder invasion success. On the other hand, ´ideal weed hypothesis´ and ´novel weapon hypothesis´ seem to be crucial for silver maple naturalisation. Palm maple failed in all studied aspects, indicating colonisation stage of the invasion process.

Phytochemical investigation of Cuscuta campestris Yunck. stem extract and evaluation of its bioherbicidal effect on Amaranthus retroflexus L. and Portulaca oleracea L.

This study focused on characterizing chemically and evaluating in vitro allelopathic and bioherbicidal potential of secondary metabolites extracted from the stem of Cuscuta campestris in seed germination, early seedling growth and early plant growth of Amaranthus retroflexus and Portulaca oleracea. The combined effects of stem extract and a reduced dose of herbicide metribuzin were also examined. Plant extract contained 17 phenolic compounds and the most abundant phenols were flavonoids: quercetin, (+)-catechin, daidzin, luteolin, and rutin. The seeds of P. oleracea were less sensitive than the seeds of A. retroflexus. The seed bioassay confirmed the inhibitory effect of stem extract on germination and early growth of both weed seedlings at concentrations of 0.75% and 1%, and a minor inhibitory effect in the plant bioassay. On the other hand, a synergy of C. campestris stem extract and metribuzin was revealed, as their combination achieved better results in the control of both weed species. Based on obtained data C. campestris stem extract could be a potential source of natural-based weed control molecules.

Bohemian Knotweed Reynoutria × bohemica Chrtek et Chrtková Seems Not to Rely Heavily on Allelopathy for Its Persistence in Invaded Sites in the Southwest Part of the Zagreb, Croatia.

Notorious invasive Bohemian knotweed Reynoutria × bohemica Chrtek et Chrtková is a hybrid of two species, Reynoutria japonica Houtt. and Reynoutria sachalinensis (F. S. Petrop.) Nakai in T. Mori which spontaneously developed in Europe, outside the natural distribution of its parental species. Its success could potentially lie in its allelopathic activity, which was confirmed in a number of experiments conducted with the leaf and root exudates, testing their effect on the germination and growth of various test plants. Here, we tested its allelopathic potential using different concentrations of leaf exudates on two test plants, Triticum aestivum L. and Sinapis alba L., in Petri dishes and pots with soil and by growing test plants in the soil sampled in knotweed stands on the edges of stands and outside of stands. Tests in Petri dishes and pots with soil to which leaf exudates were added have shown a decrease in germination and growth in comparison to the control, hence confirming the allelopathic effect. However, this was not confirmed in a test with in situ soil samples, where no statistically significant differences were observed, neither in the growth of test plants nor in the chemical characteristics (pH, soil organic matter, humus content) of the soil. Therefore, the persistence of Bohemian knotweed at already invaded sites could be attributed to its efficient use of resources (light and nutrients) through which it outcompetes native plants.

Phenolic content, antioxidant and allelopathic potential of Artemisia brevifolia Wall. ex DC. across the elevations of Western Himalayan region of Ladakh

Phenolic content, antioxidant and allelopathic potential of Artemisia brevifolia Wall. ex DC. across the elevations of Western Himalayan region of Ladakh

Total Phenolic Exudation and Allelopathic Potential of Sunflower Residues as Sustainable Weed Management

Total releasing phenolic compounds and allelopathic potential of the three sunflower genotypes Helianthus annuus L. residues were evaluated under open field conditions on weed flora associated with the proposed crops; wheat, broad bean and flax which are cultivated usually after the sunflower crop as successive crops. After getting seed from the sunflower crop. After getting seeds, sunflower plant parts were chopped and incorporated with field soil using a rotavator. Regarding the phenolics, total phenolic compounds released from sunflower residues were increased in-field soil and reached the highest concentration in the fourth week after mixing with soil. Significant suppression of weed flora was observed when the weed density and weed dry matter were reduced. Sakha sunflower genotype had the most effect, while Ishaqi genotype had the least amount of phenolic compounds. The residue of the Sakha genotype effectively suppressed over 80% of targeted weeds. The results indicate that the allelopathic potential of sunflower residues can cause suppression of weed flora which can be useful as an attractive alternative natural way to reduce synthetic herbicides as sustainable weed management.

Phytochemical screening and allelopathic potential of phytoextracts of three invasive grass species

Undoubtedly, it is important to remain vigilant and manage invasive grasses to prevent their spread and mitigate their negative impact on the environment. However, these aggressive plants can also play a beneficial role in certain contexts. For example, several invasive grasses provide valuable forage for livestock and have disease control potential. Therefore, a research experiment was conducted to explore the pros and cons of this approach, not only for surrounding vegetation but also for human and animal disease control. The study is primarily focused on developing livestock feed, plant-derived herbicides, and an understanding of the phytotoxic effects of invasive species. All plant parts of Cenchrus ciliaris L., Polypogon monspeliansis L., and Dicanthium annulatum (Forssk.) Stapf, were tested for their phyto-chemical screening, proximate, and toxicity analysis which was caused by the methanolic extract of these grass species. Qualitative phytochemical screening tests were performed for proximate composition analysis and toxicity assessment essays. The phytochemical analysis revealed the positive results for alkaloids, flavonoids, coumarins, phenols, saponins, and glycosides, while negative for tannins. Comparison of proximate analysis intimated maximum moisture (10.8%) and crude fat (4.1%) in P. monspeliensis, whereas maximum dry matter (84.1%), crude protein (13.95%), crude fiber (11%), and ash (7.2%) in D. annulatum. Five (10, 100, 500, 100, 10,000 ppm) and three (10, 1000, 10,000 ppm) different concentrations of methanolic extract prepared from C. ciliaris, P. monspeliansis, and D. annulatum were used respectively for root inhibition and seed germination essay. Furthermore, three different concentrations (10, 30, 50 mg) of plant fine powder were used for sandwich method test. There was a significant decline in the growth rate of experimental model radish seeds (P > 0.005), and results from sandwich method tests showed suppressed growth of root hairs, inhibiting the anchoring of the radish seed. In comparison, results manifest that; P. monspeliansis indicated an upsurge of inhibition (66.58% at 10,000 ppm), D. annulatum revealed soar germination (75.86% in controlled conditions), and C. ciliaris exhibited dramatic shoot up of inhibition because of sandwich method test (14.02% at 50 mg). In conclusion, although grasses are toxic, it is important to consider the beneficiary account.

Allelopathic potential of root and leaf aqueous extracts of invasive alien plant species, Cryptostegia grandiflora, on germination and seedling growth of Linum usitatissimum and Guizotia abyssinica

C. grandiflora has been termed the worst invasive alien plant species. However, its allelopathic potential has not been studied yet. The goal of this research was to study the allelopathic potential of C. grandiflora on the germination and seedling growth of L. usitatissimum and G. abyssinica. Plant specimens and samples of C. grandiflora were collected from the Minjar-Shenkora district, North Shewa Zone, Ethiopia. An experimental investigation was conducted to check the impact of its leaf and root extracts on the growth and germination parameters of the indicated test plant species. The root and leaf samples were extracted with water and methanol (99.85%). Leaf and root samples of 25 g were steeped separately in 250 ml of each of the specified solvents to make the stock solutions. The experiment was conducted in 9-cm-diameter Petri-dishes and laid out in completely random designs, replicated thrice with five blocks, each block representing a different concentration of extract (25, 50, 75, and 100%) and control. Twenty-five seeds of each test plant were placed in a petri-dish along with five ml of each extract. Differences between treatments were evaluated using one-way-ANOVA and Tukey's Honestly Significant Difference (HSD) Test. Results revealed that the inhibitory effect of water extracts of roots and leaves samples was concentration-dependent. With leaf extracts as opposed to root, the inhibitory effect was more pronounced. Hence, when L. usitatissimum seeds were treated with 100% concentration of water extracts from leaf samples of C. grandiflora germination-percentage, seedlings dry-weight, plumule, and radicle length were reduced by 80, 79.3, 73.6, and 79.4% respectively compared to the control. The above parameters also dropped considerably when G. abyssinica seeds were treated with the indicated concentrations. Conversely, the germination of seeds from both test plant species was entirely inhibited in methanol extracts. From this study, it can be deduced that these invasive plant extracts have herbicidal properties. Further phytochemical and molecular study is recommended to identify the active ingredients of C. grandiflora and determine their characteristics. Besides, the integration of identified allelopathic substances as a tool in the management of invasive species is proposed as an environment-friendly option to lessen the deterioration of ecosystem services.

Does subjecting plants to water stress enhance biological nitrification inhibition potential of rice?

Biological nitrification inhibition (BNI) is a trait that could improve nitrogen-use efficiency of a crop. We studied varietal differences in BNI potential of rice at the vegetative phase when plants were subjected to water stress. We obtained water-soluble root exudates (RE) and water-extracts of crushed root tissues (RT) from two-week-old seedlings of five rice cultivars grown continuously under adequate water or under water stress and assessed their ability to suppress the activity of Nitrosomonas europaea and the growth of lettuce seedlings. We also investigated how growing rice under continuously saturated (TC) and unsaturated (TU) soil moisture conditions affected potential nitrification rate (PNR) and community structure of ammonia-oxidizing bacteria (AOB) in the rhizosphere compared with bulk soil. We observed that only RT at ≥ 0.50 mg ml−1 suppressed the activity of N. europaea with significant (p < 0.05) differences among rice cultivars. Subjecting rice cultivars PI312777 and PI338046 to water stress significantly (p < 0.05) increased BNI of RT. Inhibition of lettuce root growth by RT was strongly correlated with its BNI (r = 0.83, p < 0.05). In T-RFLP profiles of AOB, the relative abundance of T-RF R205 was lower in TU than in TC in all cultivars except Rexmont. The rice cultivars studied produced compounds that could inhibit ammonia oxidizers, but the degree of BNI differed based on the moisture stress experienced by the crop. Lineages of rice cultivars with known allelopathic potential would be promising candidates to consider for BNI potential.

Piper nigrum allelopathy on the germination and initial growth of Lactuca sativa and Panicum maximum

The increased demand for food promotes greater use of agricultural inputs and pesticides used in pest control. Many of these products have negative environmental and public health impacts. Thus, there is a need for alternative products, with allelopathic capacity that reduce such impacts. The objective of this work was to verify the allelopathic potential of Piper nigrum L. extracts on the germination and initial growth of Panicum maximum Jacq. and Lactuca sativa seeds. The experimental design used was completely randomized, using two plant organs (leaf and seed), three extractors (hexane, ethyl acetate and methanol) and five concentrations (0 mg/L, 200 mg/L, 400 mg/L, 600 mg/L and 800 mg/L). It was verified the influence of these extracts on germination speed index (IVG), germination percentage (G), mean germination time (TMG), allelopathy index (IA), shoot growth (CPA) and in the root growth (CR) of seeds and seedlings. The leaf and seed extracts, at all concentrations and extractors tested, did not show phytotoxicity or had a very small inhibitory effect on germination and initial growth of Lactuca sativa. For Panicum maximum, ethyl acetate and methanol seed extracts, at the highest concentrations tested, had the most significant negative effects on the weed. Thus, it was possible to infer that extracts from Piper nigrum seeds have potential use in the control of the weed Panicum maximum.

Pyrus calleryana extracts reduce germination of native grassland species, suggesting the potential for allelopathic effects during ecological invasion.

Invasive plant species' success may be a result of allelopathy, or the release of secondary metabolites that are harmful for surrounding plant species. Allelopathy can be mediated through the abiotic environment by chemical sorption or transformation, so the substrate on which interactions occur can lead to differential outcomes in allelopathic potential. One aggressive invader, Pyrus calleryana, has become dominant in many ecosystems throughout Eastern US, and has reduced the abundance of native species where it invades. Thus, our goal was to identify if P. calleryana had allelopathic potential by testing the impact of leaf and flower leachate on gemination of six common grassland species (three grasses and three forbs) in either sterilized sand or field collected soils. Germination of five out of six tested species was reduced by P. calleryana leaf litter, with weaker impacts from flower leachate. This suggests that allelopathy is one mechanism driving the success of P. calleryana and that allelopathic effects may change with plant phenology. For instance, P. calleryana has late leaf senescence in the fall and copious blooming in the spring that may elongate the timeframe that allelopathic inhibition can occur. Further, germination was higher in sand than in soil, suggesting that the context of the abiotic environment can mediate this relationship. In our study, two grass species that could be overabundant in restored grasslands had higher germination rates in soil than sand and one was not altered by P. calleryana suggesting that this relationship could further promote the overabundance of grass species. Taken together, P. calleryana likely inhibits the germination of native species where it invades, but there is context dependency of this relationship with both soil chemistry and seasonality.

Allelopathic potential of radish (Raphanus sativus L.) on germination and seedling growth of some plants species.

Allelopathic potential of radish (Raphanus sativus L.) on germination and seedling growth of some plants species.

Allelopathic Potential of Marsdenia tenacissima (Roxb.) Moon against Four Test Plants and the Biological Activity of Its Allelopathic Novel Compound, 8-Dehydroxy-11β-O-Acetyl-12β-O-Tigloyl-17β-Marsdenin.

Plant parts and extracts that are rich in bioactive substances with allelopathic potential can be explored as a possible alternative to herbicides for natural weed control in sustainable agriculture. In the present study, we investigated the allelopathic potential of Marsdenia tenacissima leaves and its active substances. Aqueous methanol extracts of M. tenacissima showed significant inhibitory activities against the growth of lettuce (Lactuca sativa L.), alfalfa (Medicago sativa L.), timothy (Phleum pratense L.), and barnyard grass (Echinochloa crusgalli (L.) Beauv.). The extracts were purified through various chromatography steps, and one active substance was isolated and determined by spectral data to be a novel compound, assigned as steroidal glycoside 3 (8-dehydroxy-11β-O-acetyl-12β-O-tigloyl-17β-marsdenin). Steroidal glycoside 3 significantly inhibited the seedling growth of cress at a concentration of 0.03 mM. The concentrations needed for 50% growth inhibition of the cress shoots and roots were 0.25 and 0.03 mM, respectively. These results suggest that steroidal glycoside 3 may be responsible for the allelopathy of M. tenacissima leaves.

Effect of Allelopathic Potential of some Plants Root Exudates Concerning Growth and Pathogenicity of some Fungus on Brassica oleracea Varplant

The study aims to evaluate the effectiveness of allelopathic exudates of five plant species, namely (maize, barley, Sunflower, chard, and mung bean) concerning the release of organic substances exudated from their roots and their effect on the germination and growth of brassica oleracea var plant, as well as their impact on the growth of two isolated fungi, Rhizoctona solani and Pythium ulitmum. According to the laboratory results, chard root exudates had the highest rate of Brassica oleracea var seed germination, reaching 100%, while maize plant exudates had the lowest rate, 23.33%, compared to the control treatment, which was 100%. Sunflower and mung bean plant exudates had germination rates of 50, 43%, respectively, while barley exudates had a germination rate of 90%. Furthermore, the laboratory results also revealed discrepancy in the above-mentioned root exudates regarding the reduction of the diagonal growth of the two fungi, R.solani and P. ulitmum. Obviously, 10-day-old chard root exudates outperformed in reducing the diagonal growth of both fungi, with an average colony diameter of 0.00 cm for P. ulitmum and 1.59 cm for R.solani when compared by the control treatment (water only), which amounted to 9.00 cm. On other hand, Sunflower root exudates had the highest diagonal growth of the two fungi was reaching to 4.86 cm for R.solani and 8.50 cm for P. ulitmum. The chemical analysis of these five plants’ exudates shows that the highest concentration of the terpene compound was obtained by separating this compound from chard root exudates, using HPLC method, which amounted 3.55 55 μg/g. While the least concentration was in the maize treatment, which reached 15 μg/g. Whereas the total phenolic compounds were more concentrated in the root exudates of mung bean, which reached 52.69 μg/g, and the lowest concentration was in the root exudates of Sunflower reaching 7.89 μg/g. With regard to, the ferulic acid compound, the highest rate was observed in the root exudates of mung bean, which amounted to 19.87 μg/g, then, chard control comes in second place in which the concentration reached 10.25 μg/g. while the least concentration of the same compound was in Sunflower root exudates reached 5.69 μg/g. Seemingly, the diversity and variation of concentrations of allopathic compounds exudated from the roots of these plants, which may either negatively or positively affect the germination of Brassica oleracea var plant and the accompanying pathogenic fungi, are considered to be the cause of the varying effect of the understudied plant roots’ metabolites on germination percentages of Brassica oleracea var plant as well as in the reduction of the diagonal growth of the both fungi, R. solani and P. ulitmum.