Potential Allelopathic Effects Research Articles

Allelopathic effects of Thuidium kanedae on four urban spontaneous plants

The spontaneous plant landscape is a key focus in the development of urban environments. While many spontaneous plants can coexist with bryophytes to create appealing wilderness landscapes, the potential allelopathic effects of bryophytes on the growth of neighboring spontaneous plants remain uncertain. This study evaluated the allelopathic impact of Thuidium kanedae aqueous extracts on the germination and seedling growth of prevalent urban spontaneous plants by analyzing seed germination, seedling growth morphology, and associated indices. We also investigated the allelopathic potential of the predominant compounds in the extract on seed germination. Our findings reveal that the aqueous extract significantly impeded the seed germination of Ophiopogon japonicus, Taraxacum mongolicum, and Viola philippica, with the level of inhibition correlating positively with concentration. In contrast, Senecio scandens seed germination showed a concentration-dependent reaction, with low concentrations promoting and high concentrations hindering germination. The extract consistently reduced root length in all four species, yet it appeared to increase root vigor. The chlorophyll content in O. japonicus and V. philippica seedlings reached a maximum at a concentration of 5 g/L and decreased with higher extract concentrations. The treatment resulted in elevated catalase and soluble protein levels in the seedlings, indicating that the extract induced stress and enhanced the stress resistance index. L-phenylalanine and 2-phenylethanol, substances present in the extract, were notably inhibitory to seed germination across all species, except for O. japonicus. Notably, 2-phenylethanol exhibited a stronger allelopathic effect than L-phenylalanine. Allelopathy synthetical effect evaluation showed that high concentration of aqueous extract allelopathic inhibition effect on seed germination of four plant species, but allelopathic promotion effect on physiological and biochemical growth of Taraxacum mongolicum, Senecio scandens and Viola philippica. In summary, the study demonstrates that bryophytes exert allelopathic effects on neighboring spontaneous plants, with the degree of influence varying among species. This suggests that the germination and growth of spontaneous plant seeds may be selective in bryophyte-dominated habitats and that the density of bryophytes could shape the evolution of these landscapes.

Phytotoxic Effects and Potential Allelochemicals from Water Extracts of Paulownia tomentosa Flower Litter

Flowers of Paulownia spp. wither and fall on a large scale after blooming in spring and have potential allelopathic effects on surrounding plants, including crops and weeds. In this study, the phytotoxic effects of water extracts of Paulownia tomentosa flower litter (EPF) on wheat (Triticum aestivum L.), lettuce (Lactuca sativa L.), green bristlegrass (Setaria viridis L.) and purslane (Portulaca oleracea L.) were evaluated in the laboratory. The mode of action of the phytotoxicity of EPF on lettuce seedlings was studied and the secondary metabolites in EPF were analyzed by liquid chromatography high-resolution mass spectrometry (LC-HRMS). The results show that EPF significantly inhibited the seed germination and seedling growth of four target plants in a concentration-dependent manner. In addition, EPF could induce the excessive accumulation of reactive oxygen species (ROS) flowing with oxidative damage of the lipid bilayer of the biofilm, resulting in reduced cell viability and even apoptosis in lettuce. There were 66 secondary metabolites identified by LC-HRMS in P. tomentosa flowers. Among them, 10 compounds, including salicylic acid, caffeic acid, parthenolide, 7-hydroxycoumarin and abscisic acid (ABA), were all known allelochemicals. In summary, P. tomentosa flower litter displayed significant allelopathic effects, which were related to the accumulation of ROS in target plants. Phenolic acids, flavonoids as well as ABA are probably the main allelochemicals of P. tomentosa flowers.

Phytochemical profile and allelopathic potential of Haloxylon scoparium Pomel (Chenopodiaceae) from Algerian Sahara

The aim of the present work is to study the chemical composition, to estimate the phenolic compounds content and to evaluate the potential allelopathic effects of the Haloxylon scoparium Pomel. Phytochemical tests revealed that Haloxylon scoparium contains tannins, saponins, coumarins, alkaloids, flavonoids and steroids. Furthermore, it contains high levels of total phenolic (588.33 mg GAE 100 g-1) and flavonoids (95.45 mg QE 100 g-1) contents. Moreover, LC-MS-MS analysis allowed us to determine their chemical composition. The results of this characterization confirm the presence of vanillin, naringenin, folic acid, maleic acid, benzoic acid, myricetin, qwuercetin, beta-carotene, butylhydroxyanisole (BHA), butylated hydroxytoluene (BHT), rutin, cafeic acid, hydroxy-4-coumarine, ascorbic acid, and gallic acid. The allelopathic effect was studied on seed germination and seedling growth of four weed species. The bioassays were performed using different concentrations (1 %, 2.5 %, 5 % and 10 %) against a negative control. The seed germination, shoot and root length of weed species were completely inhibited at the highest concentrations (10 %, 5 %). However, the lower concentrations exhibited lesser inhibition percentages on the germination and the seedling growth. The phytochemical results and the significant allelopathic effects of the plant extract suggest that this species may offer new substances for the biocontrol of weeds.

Assessing the effects of Pennisetum glaucum on the soil properties, growth, nutritive, and physiological aspects of the edible pulse crop (Vigna radiata L. Wilczek)

Mung bean cropping plays a vital role in providing essential nutrition and serving as a significant summer crop to feed billions of people worldwide. However, allelopathy poses a threat to the sustainability and productivity of this system. The residues of pearl millet plants contain allelochemicals that can negatively impact weed growth in various crops. This study aimed to evaluate the potential allelopathic effects of pearl millet powder on the germination, growth, pigments, protein, and carbohydrate levels of mung beans. Different quantities of whole plant powder, namely 0, 5, 10, and 15 g of pearl millet, were blended into medium-sized pots, each containing 500 g of soil. Mung bean seeds were grown in these pots for 3–4 days in a greenhouse before transplanting them into an open field. The findings revealed that as the quantity of pearl millet powder increased, the germination percentage, germination speed, plant height, fresh weight, dry weight, chlorophyll content, carotenoid, protein, and carbohydrate amount of mung beans decreased. The physio-chemical properties of soils treated with pearl millet exhibited higher pH, conductivity, total solids, and heavy metal content than control soils. The decrease in the aforementioned attributes in soils treated with pearl millet powder could be due to the release of allelochemicals and/or the accumulation of heavy metals in the soil.These results demonstrate that using pearl millet as an herbicide to control weeds is effective, but caution must be exercised if heavy metals accumulate in the pearl millet tissue.

Enhancing Biocontrol of Harmful Algae Blooms: Seasonal Variation in Allelopathic Capacity of Myriophyllum aquaticum

Myriophyllum aquaticum has shown potential allelopathic effects for the biocontrol of cyanobacteria and cyanotoxins. However, the composition of allelochemicals and their biological effects may be influenced by seasonal changes. In this study, we investigated the impact of aqueous extracts of M. aquaticum collected in different seasons on the growth of Microcystis aeruginosa and the concentration of microcystin-LR. Plant samples were extracted using ultrasound cycles in aqueous solutions, and extracts at varying concentrations (0.1, 10, and 100 mg/L) and a control treatment were inoculated with M. aeruginosa, and cell growth was analyzed using a Neubauer chamber. Photosynthetic pigment quantification was used to measure physiological effects and liquid chromatography was used to evaluate the microcystin-LR concentrations. The extracts of plants collected during autumn and winter exhibited higher inhibition of M. aeruginosa growth and a reduction in photosynthetic pigments compared to those collected during spring and summer. These results can be explained by the higher presence of phenolic compounds in the composition of extracts from autumn and winter. Microcystin-LR concentrations were decreased at 10 and 100 mg/L, with the highest efficiency observed in autumn, while spring showed lower efficiency. Our findings suggest that M. aquaticum extracts have inhibitory potential on M. aeruginosa, particularly during the autumn season, making them a promising nature-based solution for the biocontrol of harmful algal blooms.

Allelopathic Effects of Cannabis sativa L. Aqueous Leaf Extracts on Seed Germination and Seedling Growth in Durum Wheat and Barley

In this study, the allelochemical-induced effects of the leaf water extract of hemp (Cannabis sativa) on seed germination and seedling growth were investigated in durum wheat (Triticum durum) cv. Mongibello and barley (Hordeum vulgare) cv. Alamo. The seeds were imbibed in 25%, 50%, 75%, or 100% solution concentrations, obtained from a 2% hemp leaf extract, and they were germinated at 20 and 10 °C. The 2% extract stock solution (i.e., 100% solution concentration) was obtained by extracting 20 g of leaf powder in 1 L distilled water (2%, w/v). A control of seeds imbibed in distilled water was considered. Germination was scored daily and at the end of the germination test, the final germination percentage (FGP), mean germination time (MGT), germination index (GI), and vigor index (VI) were calculated. The radicles and shoots of the germinated seeds of both species were also measured for their length and weight. The analyses revealed the presence of phenols in the hemp leaf extract, which were the highest in the 100% concentration (13.14 ± 0.20 mg gallic acid equivalent-GAE g−1 extract). At 20 °C, increasing the concentration had either minor (in wheat) or no effects (in barley) on the seed germination. At 10 °C, the germination was reduced by the increasing concentration, suggesting a potential allelopathic effect of the extract. However, at 100% concentration, the seeds germinated significantly better that those at 75% concentration. At 20 °C, increasing concentration progressively depressed both the radicle and shoot elongation in both species. At 10 °C, the radicle elongation was depressed by the extract, irrespective of the concentration, whilst the shoots were as long as those of the control in wheat, and smaller at the 50 and 75% concentrations in barley. We can conclude that the water extract of hemp leaves can have a negative impact on wheat and barley seed germination and seedling growth, particularly at temperatures below optimal. However, the high concentration of phenols in the extract may stimulate seed germination and seedling growth. Thus, in semi-arid areas, such as those of the Mediterranean regions, sowings of wheat and barley after hemp at an optimal (i.e., 20 °C) or nearly optimal temperature are recommended in order to minimize the combined stressing effects of the temperature and allelopathic leaf extract upon plant establishment, which may limit a successful crop establishment.

The monodominance of Acuri in Pantanal formations: allelochemical effects of its leaves and the presence of Acurizais.

The presence of monodominant vegetative formations almost exclusively composed of Acuri palm trees (Attalea phalerata) stands out in some regions of the Pantanal Sul-Mato-Grossense. These formations are generally associated with anthropic, edaphic and/or hydrological factors. However, little is known about the effect of allelopathy on the formation and maintenance of these areas. Herein, we investigated the chemical composition of A. phalerata aqueous leaf extract and the potential allelopathic effects on germination and growth of target L. sativa, L. esculentum and S. obtusifolia species. Thus, extracts at concentrations of 0, 2.5, 5, 10, 15, and 20% were used for germination and growth bioassays with a completely randomised design in a germination chamber and greenhouse. The results showed that the A. phalerata extracts negatively affected the germination speed index and mean germination time of the target species and positively affected seedling length under controlled conditions and were also stimulated in the greenhouse. Thus, the formation of Acurizals can be related to the presence of secondary metabolites in the leaves, in addition to other environmental factors.

Allelopathic potential of native species on weeds in Morelos, Mexico associated with the cultivation of corn

The main objective of the study was to identify native plants of the State of Morelos with allelopathic potential associated with the cultivation of corn, which could be involved as a Push-Pull strategy. Aqueous extracts of thirty collected weed species were applied against two white species, evaluated by a new sandwich microbioassay in Elisa plates, in parallel with a plate bioassay. Effects on germination, root growth and hypocotyl were calculated. A second trial evaluated the allelopathic potential of weeds on the growth of Parthenium hysterophorus under semi-controlled conditions, recording the total effect, foliar and root interaction without barriers, competition for cover and root interaction, to then calculate the root interaction (IR) based on the witness. The results indicated that the medium doses 2.5% w/v and high doses 5% w/v of aqueous extracts of the weeds Rhynchosia minima, Antigonon leptopus, Ipomoea tricolor, Ipomoea triloba, Calopogonium mucunoides, Crotalaria pumila and Ipomoea hederifolia, show inhibitory activity on the germination and growth of Amaranthus hypochondriacus and Panicum maximum. All the residues inhibited the germination and growth of the weeds, increasing their activity when increasing the dose. Species with allelopathic potential could be evaluated in a program that involves the Push-Pull strategy associated with maize cultivation. Seven native species with potential allelopathic effect were identified by means of a fast and economic protocol such as sandwich microbioassay, in addition, the weeds with the highest inhibition were verified using two doses of residues, and the predominant effect of three species of Convulvulaceae was illuminated, in the inhibition with interaction. root on weeds.

Antioxidant activity, phytotoxicity and allelopathic potential of green walnut (Juglans regia L.) fruit extract

The potential allelopathic effect of a green walnut fruit extract on seed germination and early growth of three weed species (Chenopodium album, Amaranthus retroflexus, Daucus carota) was tested, as well as its phytotoxic effect on seed germination and early growth of maize (Zea mays). Another objective was to analyze the plant extract and assess its antioxidative activity. Antioxidative activity of the plant extract was evaluated based on its ability to neutralize DPPH (2,2-diphenyl-1-picrylhydrazyl) radical and capacity for iron reduction using the FRAP method. Inhibition of the evaluated parameters (total germination and seedling length) decreased proportionally with decreasing concentrations of extract solution of green walnut fruit. The parameters of seedling growth were also found to show greater susceptibility than total seed germination of all three of the tested weed species. Although the seed bioassay results indicated a high inhibitory effect on germination and early growth of the tested weeds, they also revealed phytotoxic activity during early growth of the cultivated Z. mays.

Potential Allelopathic Effect of Wheat Straw Aqueous Extract on Bermudagrass Noxious Weed

Residues of several crops, including wheat, have a promising allelopathic effect on noxious weed species and thus represent eco-friendly alternatives to harmful, widely applied herbicides. The current investigation deals with the effects of wheat straw aqueous extract on the growth and biochemical aspects of bermudagrass (Cynodon dactylon L.) as a model of harmful weeds for the wheat crop. The prepared aqueous extract from wheat straw was subjected to high-performance liquid chromatography (HPLC) analysis to identify and quantify phenolic and flavonoid components. In addition, the allelopathic effect of different concentrations of the extract on the germination, seedling growth, and biochemical aspects of bermudagrass was assessed. Our findings showed a significant decrease in bermudagrass seed germination percentage (ranging from 29.6 to 82.4%) and germination index (ranging from 10.07 to 32.43) in response to the extract treatments and a significant decline in all morphological growth parameters of the seedling. HPLC analysis of the extract showed the presence of seven phenolic acids and six flavonoids. The most prevalent phenolics included pyrogallol (13.75 µg/g), ferulic acid (9.82 µg/g), gallic acid (8.5 µg/g), and isoferulic acid (4.47 µg/g), while the predominant flavonoids included catechin (11.04 µg/g), luteolin (8.26 µg/g) and quercetin (7.74 µg/g). The highest extract concentrations (75% and 100%) showed a corresponding decline in the leaf content of chlorophylls a and b but a significant increase in the content of free amino acids, total protein and soluble carbohydrates. Superoxide dismutase (SOD) activity exposed a concentration-dependent reduction, while the activities of both catalase (CAT) and ascorbate peroxidase (APX) were reduced only with the highest extract concentration. The principal component analysis (PCA) showed a high correlation among the morphological growth parameters, indicating that these elements either have a common ground of variance or are inter-correlated. Accordingly, our findings suggest the possibility of combating bermudagrass weeds using the aqueous extract of wheat straw.

Evaluation of Allelopathic Potential of Pluchea indica on Brassica chinensis and Zea mays

Weeds have become one of the leading causes of crop production losses, including the cost of weed management, weed crop competition, and weed intervention with crop management practices. Moreover, herbicide use in agricultural systems is currently being debated due to the potential adverse effects on the environment and human health. The utilization of the allelopathic phenomenon is widely considered an alternative weed management strategy. However, allelopathic study of Pluchea indica plant was limited. P. indica is a flowering plant under family Asteraceae, locally known as Beluntas. Thus, this study was conducted to determine the allelopathic effects of the aqueous leaf extract of P. indica on the seedling growth of tested plant species and to investigate the effect of P. indica leaf debris on the growth of tested plant species. In this study, the allelopathic potential of P. indica leaves were investigated through petri dish bioassay and soil bioassay method. The two tested plant species were chosen for the bioassay: monocotyledonous; maize (Zea mays) and dicotyledonous; mustard (Brassica chinensis). These tested plant species were chosen for the experiment due to their known quick seedling growth behaviours and commonly used in allelopathic studies. The result showed that as the concentration of aqueous leaf extract increased, the inhibition percentage of the radicle length of B. chinensis and Z. mays were increased. However, stimulatory effect was observed on the radicle length of B. chinensis and Z. mays when 1.3%and 2.5% w/w P. indica leaf debris were applied. Thus, aqueous leaf extract and leaf debris of P. indica have potential allelopathic effects on the growth of B. chinensis and Z. mays. Further studies need to be conducted on other bioassay species especially weed species, to elucidate the allelopathic potential of P. indica in weed control.

Can allelopathy of Phragmites australis extracts aggravate the effects of salt stress on the seed germination of Suaeda salsa?

Phragmites australis is highly adaptable with high competitive ability and is widely distributed in the coastal wetland of the Yellow River Delta. However, allelopathic effects of P. australis on the growth of neighboring plants, such as Suaeda salsa, are poorly understood. In this study, germination responses of S. salsa seeds collected from two different habitats (intertidal zone and inland brackish wetland) to the extracts from different part of P. australis were compared. Potential allelopathic effects on germination percentage, germination rate, radicle length, and seedling biomass were analyzed. The germination of S. salsa was effectively inhibited by P. australis extract. Extract organ, extract concentration, and salt concentration showed different effects, the inhibitory rates were highest with belowground extract of P. australis between the four different parts. Germination percentage and germination rate were significantly decreased by the interactive effect of salt stress and extract concentration in S. salsa from a brackish wetland but not in S. salsa from the intertidal zone. The impact of different extracts of P. australis on radicle length and seedling biomass of S. salsa showed significant but inconsistent variation. The response index results showed that the higher concentration of extract solution (50 g·L−1) of P. australis had stronger inhibitory effect on the seed germination and seedling growth of S. salsa while the belowground extract had the strongest negative effect. Our results indicated that allelopathy is an important ecological adaptation mechanism for P. australis to maintain a high interspecific competitive advantage in the species’ natural habitat.

Plant invasion modifies isohydricity in Mediterranean tree species

Abstract Understanding of plant hydraulic strategies (i.e. the degree of iso‐/anisohydricity) is crucial to predict the response of plants to changing environmental conditions such as climate‐change induced extreme drought. Several abiotic factors, including evaporative demand, have been shown to seasonally modify the isohydricity of plants. However, the impact of biotic factors such as plant–plant interactions on hydraulic strategies has seldom been explored. Here, we investigated adaptations and changes in hydraulic strategies of two woody species in response to seasonal abiotic conditions, experimental drought and plant invasion in a Mediterranean cork oak (Quercus suber) ecosystem with a combined shrub invasion (Cistus ladanifer) and rain exclusion experiment. From the dry to wet season, Q. suber shifted from a partial isohydric to an anisohydric behaviour while C. ladanifer shifted from strict anisohydric to partial isohydric. During drought, water competition by plant invasion significantly modified the hydraulic strategy of invaded Q. suber, which was accompanied by lower pre‐dawn leaf water potentials, sap flow density, leaf area index and trunk increment rates. This altered isohydricity of invaded Q. suber trees was most likely caused by interspecific competition for water resources by water spending C. ladanifer shrubs. Both species do have the highest proportion of fine roots in the topsoil and thus, an additional water consumer, such as C. ladanifer can lead to more stressful conditions for Q. suber during times of water scarcity. Further underlying mechanisms of the altered isohydricity of Q. suber, such as potential allelopathic effects of C. ladanifer exudates on root growth of Q. suber, have to be investigated in the future. In conclusion, we demonstrate that the degree of isohydricity of two woody Mediterranean plant species is dynamically determined by the interplay of species‐specific hydraulic traits and their abiotic and biotic environment. Read the free Plain Language Summary for this article on the Journal blog.

Effect of forage aqueous extracts on Glycine max L. Merr., Zea mays L. and Bidens pilosa L.

The aim of the present study was to investigate the potential allelopathic effects of isolated or intercropped aqueous forage extracts on the physiological performance of soybean [Glycine max (L.) Merr.] and corn (Zea mays L.) seeds, as well as their phytotoxicity to the weed species Bidens pilosa L. Aqueous extracts were prepared at a concentration of 5%, and the tests with soy and corn were conducted by wetting the germination papers with different treatments and performing procedures within the standards of the Brazilian Rules of Seed Analysis. Tests with the cover plant extracts on the seeds of B. pilosa used BOD-type repetitions. Fifty weed seeds were placed in a gerbox with filter paper moistened with the different treatments with five repetitions. Distilled water was used as the control in all tests. Extracts of Avena strigosa Schreb and Raphanus sativus L. (radish), cultivated individually and in combination, increased the seed germination percentage (%G) and the length of soybean seedlings. Similarly, extracts of Pennisetum glaucum (L.) R.Br and Crotalaria spectabilis Roth, in individual and combined cultivation, provided gains in corn %G. Furthermore, all tested extracts suppressed germination and decreased the speed of the germination index of the hairy beggarticks when compared to the control, with the radish extract showing the greater reduction effect on the %G of the weed plant B. pilosa. Highlights: The use of Crotalaria as a cover crop has a positive effect on the initial growth of corn. The use of black oat and forage radish intercropped had the potential to increase soybean yield. The use of cover crops contributes to the integrated management of weeds. The choice of cover plant is important for the success of crop rotation.

Potential suppressive effects of Mexican poppy weed residues on germination and early growth of maize and pearl millet crops

Argemone ochroleuca allelochemical properties have been reported but not empirically tested on economically important staple cereal crops. Therefore, the objective of this study was to determine the potential Allelopathic effects of the alien weed’s residues on germination and early-growth of maize (Zea mays L.) and Pearl millet (Pennisertum glaucum). Allelopathic effects of A. ochroleuca on maize and millet seed germination were tested in a 2 (shoot and root) x 11 (0, 10, 20, 30, 40, 50, 60, 70, 80, 90 and 100g/L water) factorial treatment arrangement in CRD in an incubator placed in a laboratory. Whereas effects of the weed extracts on the same crops’ early-growth were tested in a 2 (shoot and roots) x 8 (0, 2, 4, 6, 8, 10, 12 and 14g ground-powdered extracts) factorial arrangement in RCBD under laboratory conditions. Maize and millet germination percentage, germination speed, mean germination time, mean daily germination, plumule and radicle length were measured for germination test, whereas, plant height, stem diameter, root and shoot mass were used as indicators of A. ochroleuca suppression of early plant growth. Relative to untreated control, concentration equal to and greater than 10g/L aqueous extracts of A. ochroleuca reduced millet and maize seed germination variables by 10–100% and 28–56%, respectively, while early-growth variables were reduced by 66–100% and 4–37%, respectively. Argemone ochroleuca shoot extracts were more suppressive than root extracts on germination and early growth of the two crops. In conclusion, A. ochroleuca Allelopathic effects were concentration and plant-part dependent, inhibitory effects increased with concentrations, with extracts from shoots being more Allelopathic on measured variables when compared to root extracts. As A. ochroleuca continues to spread yearly without any control strategies in place, a threat exist on maize and Pearl millet production especially in communal farming areas where improved management strategies are non- existent. Key words: Allelopathic, Argemone ochroleuca, germination, growth, millet, maize, plumule, radicle

Trade-Off between Facilitation and Interference of Allelopathic Compounds in Vegetation Recovery: The Case of Rosmarinus officinalis in Degraded Gypsum Habitats.

Rosmarinus officinalis advantageously competes with other species in restored gypsum outcrops, and further research is needed to understand the causes. Specifically, we focus on the potential allelopathic effects derived from its terpenes on the emergence of gypsum species. To this end, we established 120 circular subplots in a previously restored gypsum outcrop, and randomly applied four different treatments based on the presence/absence of rosemary plants and their leaves on the soil. Afterwards, we conducted an experimental sowing of native gypsophiles. All subplots were monitored to estimate seedling emergence, and soil and leaf samples were analysed for terpenes. The results show that the treatments had significant effects on the overall emergence of seedlings, and terpenes were found in rosemary leaves and soils, with no significant differences in terpene composition. In particular, we identified a clear negative effect in the treatment where rosemary plants were eliminated but its leaves were left along with allelopathy (2.57 ± 0.54 individuals/subplot). Unexpectedly, the presence of rosemary plants seems to facilitate the emergence of gypsum species (9.93 ± 1.61 individuals/subplot), counteracting the effects of the allelopathic substances in the soil. Consequently, we do not suggest removing rosemary plants in early stages to encourage the emergence of gypsum species in restored areas.

Invasion of the North American sand dropseed (Sporobolus cryptandrus) – A new pest in Eurasian sand areas?

For the effective control of an invasive species, gathering as much information as possible on its ecology, establishment and persistence in the affected communities is of utmost importance. We aimed to review the current distribution and characteristics of Sporobolus cryptandrus (sand dropseed), an invasive C4 grass species of North American origin recently discovered in Hungary. We aimed to provide information on (i) its current distribution paying special attention to its invasion in Eurasia; (ii) the characteristics of the invaded habitats in Central Europe; (iii) seed bank formation and germination characteristics, crucial factors in early establishment; and (iv) the effects of its increasing cover on vegetation composition. Finally, we aimed to (v) point out further research directions that could enable us to understand the invasion success of this potential invasive species. Field surveys uncovered large stands of the species in Central and Eastern Hungary with most of the locations in the former, especially in the Kiskunság region. The species invaded disturbed stands of dry and open sand grasslands, closed dune slack grasslands and it also penetrates natural open sand grasslands from neighboring disturbed habitats. Increasing cover of Sporobolus cryptandrus was associated with a decline in species richness and abundance of subordinate species both in the vegetation and seed banks, but a low density of Sporobolus cryptandrus can even have a weak positive effect on these characteristics. Viable seeds of Sporobolus were detected from all soil layers (2.5 cm layers measured from the surface to 10 cm in depth), which indicates that the species is able to form a persistent seed bank (1114 to 3077 seeds/m 2 with increasing scores towards higher abundance of the species in vegetation). Germination of Sporobolus cryptandrus was negatively affected by both litter cover and 1 cm deep soil burial. To sum up, Sporobolus cryptandrus can be considered as a transformer invasive species, whose spread forms a high risk for dry sand and steppe grasslands in Eurasia. We can conclude that for the effective suppression of the species it is necessary: (i) to clarify the origin of the detected populations; (ii) to assess its competitive ability including its potential allelopathic effects; (iii) to assess its seed bank formation potential in habitats with different abiotic conditions; and (iv) to assess the possibility of its suppression by natural enemies and management techniques such as mowing or livestock grazing. • We studied the distribution and characteristics of the invasive sand dropseed. • The species invades degraded grasslands, undisturbed sand grasslands and steppes. • With increasing dropseed cover declining plant species diversity was found. • Persistent seed banks and an effective germination of the species was detected. • Spread of sand dropseed forms a high risk for dry sand grasslands in Eurasia.

Rye (<em>Secale cereale</em> L.) and squarrose clover (<em>Trifolium squarrosum</em> L.) cover crops can increase their allelopathic potential for weed control when used mixed as dead mulch

Cover crops are essential tools in agro-ecosystems for reducing the reliance on synthetic inputs and associated environmental risks. Alongside their benefits to soil fertility, cover crops can control weeds by their competitive and allelopathic attributes. Laboratory and field experiments were conducted to assess the allelopathic potential of two cover crop species, rye (Secale cereale L.) and squarrose clover (Trifolium squarrosum L.), alone or in a mixture, on seed germination and growth of arable weeds. Aqueous extracts of the two cover crops and their mixture were tested in a bioassay on Conyza canadensis (L). Cronq., Amaranthus retroflexus L. and Digitaria sanguinalis (L.) Scop. In vitro effects of aqueous extracts varied in a dose-dependent manner, with cover crops and weed species. All three extracts were able to reduce the germination of A. retroflexus (–87%) considerably. Inhibitory effects by rye and mixture extracts on radicle growth of all weed species ranged between 51 and 82%. Rye extract was the best at reducing shoot length of C. canadensis and D. sanguinalis (–39 to 44%), while squarrose clover was more effective on A. retroflexus (–79%). Plant extracts also delayed the germination time of weed species with a substantial effect of the mixture on C. canadensis seeds. In the field experiment, no significant weed suppression was provided by cover crop residues incorporated as green manure compared to control plots, despite tillage being more effective in reducing weed density than no-till. Still, the mulch of the mixture controlled weed emergence significantly better than single cover crop mulches. The chemical characterization of cover crop residues, both shoots and roots, revealed a notable richness of allelopathic phenolic acids and flavonoids, which may constitute potential natural herbicides through slow decomposition. From the analysis of the aqueous extracts, other non-analysed and/or unidentified water-soluble allelopathic compounds should underlie the phytotoxicity observed in vitro, at least for rye. For cover crop mixture, positive interactions among plant materials leading to a better release of allelochemicals and weeding effectiveness are discussed according to chemical profiles and field data. Our study demonstrated the allelopathic activity of the cover crops and their potential to be included in weed management strategies according to cropping system needs. Additional trials are needed to confirm the performance of cover crop residues under field conditions. Highlights - Rye and squarrose clover are cover crops with potential allelopathic effects. - Aqueous extracts of residues of rye, squarrose clover, and their mixture reduced and/or slowed weed germination of A. retroflexus and C. canadensis in the in vitro bioassays. - Depending on the concentration of residues, the aqueous extracts had inhibitory effects on radicle and shoot growth of A. retroflexus, C. canadensis, and D. sanguinalis. - The mulch of a mix of rye and squarrose clover under field conditions suppressed weeds better than the single species.

Determination of the Allelopathic Potential of Cambodia’s Medicinal Plants Using the Dish Pack Method

Plants produce several chemically diverse bioactive substances that may influence the growth and development of other organisms when released into the environment in a phenomenon called allelopathy. Several of these allelopathic species also have reported medicinal properties. In this study, the potential allelopathic effects of more than a hundred medicinal plants from Cambodia were tested using the dish pack method. The dish pack bioassay method specifically targets volatile allelochemicals. Twenty-five species were found to have significant inhibitory effects on lettuce radicle growth. Eleven different plant families, including Iridaceae (2), Apocynaceae (2), Poaceae (2), Sapindaceae, Araceae, Combretaceae, Orchidaceae, Clusiaceae, Zingiberaceae, Rutaceae and Asparagaceae had the plant species with high inhibitory effects. Allophyllus serrulatus had the highest growth inhibitory effect on lettuce radicles more than 60%, followed by Alocasia macrorrhiza, Iris pallida, Terminalia triptera, Wrightia tomentosa, Cymbidium aloifolium, Garcinia villersiana and Kaempferia parviflora. The candidate species were subjected to further studies to identify the volatile allelochemicals in the volatile constituents.

Interseeding of ruzigrass into soybean: Strategies to improve forage cultivation in no-till systems

No-till (NT) farming is a major soil conservation strategy. In the Brazilian Cerrado, soybean is the main grain crop, and strategies that improve the cultivation of cover crops in the off-season in succession to soybean could facilitate NT for large cultivated areas. In the municipality of Nova Xavantina, MT, Brazil, three experiments were carried out in a randomized block design with four replications. This work aimed to evaluate the establishment of Urochloa ruziziensis (ruzigrass) in succession to soybean as a function of ruzigrass seed treatment, sowing density and phenological stage, and soybean cultivar allelopathic potential. In the first experiment, treatment of ruzigrass seeds with six doses (0, 150, 300, 450, 600 and 750 mL of commercial product 100 kg−1 of seeds) of fipronil + thiophanate-methyl + pyraclostrobin was evaluated. In the second experiment, two ruzigrass interseeding periods (soybean phenological stages R5.5 and R7) and five ruzigrass seed densities (4.3, 6.4, 8.6, 10.7 and 12.9 kg ha−1 VPS) were tested. In the third experiment, the interference of soybean cultivars in the establishment of ruzigrass and the potential allelopathic effect of the cultivars on forage germination were evaluated, six soybean cultivars RR (Roundup Ready®) were used: P98Y70; TMG 115; TMG 132; M 8527; P98Y11; TMG 123. Our results showed that seed treatment facilitated forage establishment in the interseeding system, and the use of high sowing rates at phenological stage R5.5 of soybean promoted greater ruzigrass plant development. The effects of the soybean cultivars on ruzigrass germination varied, suggesting allelopathic effects of the deposition of petioles and soybean leaves on ruzigrass seeds. Thus, an appropriate interseeding strategy can improve forage production in the off-season and favor NT through correct management of forage establishment in succession to soybean.