Showing papers on "Allelopathy published in 1997"
TL;DR: This chapter discusses compartmentation of secondary metabolites and xenobiotics in plant vacuoles, which are characterized as compounds that are not indigenously present in a particular plant species.
Abstract: Publisher Summary This chapter discusses compartmentation of secondary metabolites and xenobiotics in plant vacuoles. Plants need to protect themselves against herbivores and microorganisms. Various defense strategies can be observed in plants, which are not independent and which may operate cooperatively and synergistically. These strategies include physical protection by thorns, spikes, trichomes, glandular or stinging hairs, and the production and storage of defense chemicals, which are abundant and a typical trait of all plants. Plant surfaces are usually covered by a hydrophobic cuticle consisting of antibiotic and deterrent/repellent cuticular waxes which may contain other biologically active allelochemicals such as flavonoids. Plants can synthesize inhibitory proteins or enzymes, which could degrade microbial cell walls or other microbial constituents, or peroxidase and phenolase, which could help to inactivate microbial toxins produced by pathogens. Plants can produce and store secondary metabolites with deterrent/repellent or toxic properties against microorganisms, viruses and/or herbivores. In addition to defense, secondary metabolites are employed by plants to attract pollinating insects or seed–dispersing animals, for example by colored compounds such as betalains, anthocyanins. In this case, it can be considered that secondary metabolites are attracting signal substances. Xenobiotics can be characterized as compounds that are not indigenously present in a particular plant species. In nature, xenobiotics can be secondary metabolites, which are produced by other plants and released to the environment either via the rhizosphere or by leaching from aerial parts. A more recent exposure of plants to xenobiotics is due to agrochemicals and industrial pollutants.
168 citations
TL;DR: Allelopathy includes both positive and negative effects of one plant on the other through environment, though most of the studies seem to focus on its deleterious impacts.
Abstract: Summary Allelopathy includes both positive and negative effects of one plant on the other through environment, though most of the studies seem to focus on its deleterious impacts. It plays a key role in both natural and managed ecosystems. In agroecosystems, several weeds, crops, agroforestry trees and fruit trees have been shown to exert allelopathic influence on the crops, thus, affecting their germination and growth adversely. Some of the agricultural and horticultural crops affect their own seedlings grown in succession which is commonly known as replant problem/syndrome. Available studies indicate that allelochemicals act via bringing certain changes in physiological functions like respiration, photosynthesis and ion uptake. These, in turn, result in visible changes in seed germination, further growth reduction and overall performance of the target plants. The studies on interplant interactions assume significance in agroforestry programmes for selecting the types of crops complementary to the select...
133 citations
TL;DR: Selecting mustard green manures that release high levels of allyl-ITC would appear to be optimal for allelopathic activity, and plants that produce high level of benzyl- ITC also appear promising.
Abstract: Several members of the crucifer family (Brassicaceae), including white mustard (Brassica hirta Moench), brown mustard [B. juncea (L.) Coss], black mustard [B. nigra (L.) Koch], leafy turnip (B. campestris L.), rapeseed (B. napus L.), and garden cress (Lepidium sativum L.) were examined for their potential as allelopathic green manure crops. Hemp sesbania [Sesbania exaltata (Raf.) Rydb. Ex A. W. Hill] germination and fresh weight was inhibited by chopped leaf tissues of all green manures tested, including wheat (Triticum aestivum L.), when added to a sandy loam soil. Wheat seed germination was inhibited only by B. nigra, B. hirta, and L. sativum, although none of the treatments reduced fresh weight of germinated seedlings. The major volatiles released by chopped plants were determined by solid-phase microextraction sampling and identified by gas chromatography–mass spectrometry (GC-MS). Volatiles included allyl isothiocyanate (allyl-ITC), 3-butenyl isothiocyanate, benzyl isothiocyanate (benzyl-ITC), cis-3-hexen-1-ol, and trans-2-hexenal. These compounds, together with methyl-ITC (methyl-ITC), β-phenylethyl-ITC, benzaldehyde, β-ocimene, and α-farnesene were tested for inhibition of seed germination of several crop and weed species when applied as volatiles. Of these, allyl-ITC and methyl-ITC were the most inhibitory, completely inhibiting the germination of all species at a headspace gas concentration of 1 ppm in airtight glass containers. Selecting mustard green manures that release high levels of allyl-ITC would appear to be optimal for allelopathic activity, and plants that produce high levels of benzyl-ITC also appear promising.
129 citations
TL;DR: The planktonic freshwater cyanobacterium Trichormus doliolum released secondary metabolites that strongly inhibited the growth of other cyanobacteria and suggested that under P limitation less abundant species can exert allelopathic effects on more abundant taxa.
Abstract: The planktonic freshwater cyanobacterium Trichormus doliolum (Bharadw., ’ Komarek and Anagnostidis released secondary metabolites that strongly inhibited the growth of other cyanobacteria. The major allelopathic compound inhibited PS II-mediated photosynthetic electron transport. The allelopathlc compounds were released under P-limited and rcplcte exponential growth; the release of the major allelopathic compound, however, increased 30fold under P-limited growth. Increased irradiance under P-limited growth led tc elevated release of dissolved organic carbon, but there was no increase in release of the major allelopathic compound. This suggests that there are different control mechanisms for extracellular release of gross carbon and allelopathic secondary metaboliccs in T. d&i&m. Allelopathic compounds released by T. doliolum grown under phosphorus limit &ion significantly reduced the growth of Anabaena variubilis even when the biomass of the latter was 20-fold greater than that of T. doliolum. This suggests that under P limitation less abundant species can exert allelopathic effects on more abundant taxa.
123 citations
TL;DR: Annual wormwood leaf tissue and MeCl2-extract treatments were the only treatments that resulted in a reduction in seedling survival, germination, and growth of redroot pigweed, and the allelopathic effects of annual wormwood can not be attributed to artemisinin alone.
Abstract: Leaf tissue and leaf-tissue extracts from annual wormwood and pure artemisinin were evaluated for their effects on plant growth when incorporated into sandy loam soil. Dried leaf tissue was successively extracted with methylene chloride (MeCl2), ethanol (EtOH), and water, and the extracts and residue were reduced to dryness and stored at −20 C. Leaf tissue was incorporated in soil at rates equivalent to 0, 0.37, 0.73, or 1.1% (w/w) based on soil dry weight. Peat moss treated with extracts or artemisinin was incorporated into soil at a rate equivalent to the 0.73% (w/w) treatment. Inhibition of growth was species-specific; estimated reduction of dry weight by 0.73% (w/w) leaf tissue was 82, 49, 25, and 9% for redroot pigweed, common lambsquarters, soybean, and corn, respectively. The effects of the MeCl2 extract, which contained all of the extractable artemisinin, on germination and growth of redroot pigweed were similar to that of leaf tissue. Annual wormwood leaf tissue and MeCl2-extract treatments were the only treatments that resulted in a reduction in seedling survival. Artemisinin at levels equivalent to that contained in the MeCl2 extract and leaf-tissue treatments had significantly less effect on seedling survival, germination, and growth of redroot pigweed than the MeCl2 extract. Furthermore, the aqueous extract, which did not contain artemisinin, and the extract residue had activities similar to that of the artemisinin treatment. Thus, the allelopathic effects of annual wormwood can not be attributed to artemisinin alone.
97 citations
TL;DR: The active constituents in the inhibition of germination are low molecular weight phenolic compounds and the flavonoids appear to exert no direct effect on germination of the species tested, but do provoke a reduction in cotyledon and root size, and could thereby inhibit subsequent seedling development.
Abstract: 1. The allelopathic effect of the exudate secreted by Cistus ladanifer leaves was tested on different plant species. Cynodon dactylon and Rumex crispus, species absent from C. ladanifer scrub (jarales), were clearly inhibited by the exudate.
2. Species present in the jarales, Medicago polymorpha and Lolium rigidum, showed no direct inhibition of germination, but the process this was delayed, and cotyledon and root size was diminished. This implies inhibition of seedling growth, and may explain the low abundance of these species inside the jarales.
3. The active constituents in the inhibition of germination are low molecular weight phenolic compounds. The flavonoids appear to exert no direct effect on germination of the species tested, but do provoke a reduction in cotyledon and root size, and could thereby inhibit subsequent seedling development.
72 citations
TL;DR: Results indicate that the presence of allelochemicals on a substrate (e.g., insect cuticle or leaf) may be an additional constraint to the survival of entomopathogenic fungi.
62 citations
TL;DR: There is a possibility to harness the allelochemicals of eucalyptus leaves as herbicides for the management of these perennial weeds.
Abstract: The allelopathic potential of Eucalyptus globulus Labill. (gum tree) fresh and dried leaf leachates was studied using two perennial weeds, viz. purple nutsedge (Cyperus rotundus L.) and bermuda grass (Cynodon dactylon L. Pers) as test weeds. Aqueous leachate of fresh leaves of eucalyptus significantly suppressed the establishment of vegetative propagules and early seedling growth of the weeds. Leachate of fresh leaf cuttings had growth inhibitory effect on bermuda grass but showed growth promotion effect on purple nutsedge. Similarly the leachate of dried leaves of eucalyptus had differential influence on the growth of the two weeds. There is a possibility to harness the allelochemicals of eucalyptus leaves as herbicides for the management of these perennial weeds.
60 citations
Journal Article•
40 citations
TL;DR: Comparison with an earlier study revealed that the effects of these thermal and dietary conditions were distinctly different for prey and pred- ators, which suggests that such conditions would promote developmental asynchrony be- tween prey and predator populations.
Abstract: We examined the effects of three allelochemicals found in tomato (chloro- genic acid, rutin, and tomatine) and two thermal regimes (210:100C and 260:15'C, repre- senting spring and summer, respectively) on the performance of a generalist insect predator (Podisus maculiventris: Pentatomidae) fed prey containing those allelochemicals. The prey were Manduca sexta (Sphingidae) caterpillars, Solanaceae specialists with a preference for tomato. Whether an allelochemical had a negative, neutral, or positive effect on develop- mental time or mass gained by the predators depended on thermal regime and the com- bination of allelochemicals in the prey's diet. The effects of multiple allelochemicals were not always additive. For the most part, the allelochemicals had greater negative effects at the warmer thermal regime. Effects of allelochemicals also depended on the stage of the predator. Individually, chlorogenic acid and rutin prolonged developmental time of second- instar nymphs. In contrast, only rutin and tomatine together affected developmental time of fourth-instar nymphs, and this combination of allelochemicals reduced developmental time. Tomatine substantially reduced mass gained by second-instar nymphs but had no effect on mass gained by fourth-instar nymphs. Rutin and tomatine together had no effect on second-instar nymphs but increased the mass of fourth-instar nymphs. There were no allelochemical by temperature interactions for second-instar nymphs, whereas allelochem- ical by temperature interactions influenced stadium duration, final dry mass, and relative growth rate of fourth-instar nymphs. Rutin and tomatine together eliminated the negative effect of chlorogenic acid on consumption of prey by the fourth-instar nymphs. Chlorogenic acid by itself and rutin and tomatine together increased the efficiency of conversion of ingested prey to nymphal biomass. Comparison with an earlier study revealed that the effects of these thermal and dietary conditions were distinctly different for prey and pred- ators, which suggests that such conditions would promote developmental asynchrony be- tween prey and predator populations.
40 citations
TL;DR: Brachiaria brizantha and among grasses and Calopogonium mucunoides among legumes were the species that promoted the reduction more intensively on seed germination and radicle elongation of the receiver species, and the aerial part of the donor species was the main source of water soluble allelopathic potential compounds.
Abstract: Aqueous extracts from seeds, aerial part and roots of grasses Brachiaria humidicola, Brachiaria decumbens and Brachiaria brizantha cv. Marandu and legumes forage Calopogonium mucunoides and Stylosant hes guianensi s cv. Mineirao were prepared in a concentration of 10% (w/v), to evaluate the allelopathic potential effects on seed germination and radicle elongation of the pasture weeds: Desmodium adscendens, Sida rhombifolia and Vernonia polyanthes. Seed germination was monitored in ten-day periods, with daily countand elimination of seed germination. At the end of the ten-day periods the radicle was measure d. The osmot ic potential effects were isolated by calculation. The donor species showed allelopathic potential that varied in function of donor and receiver species. Brachiaria brizantha and among grasses and Calopogonium mucunoides among legumes were the species that promoted the reduction more intensively on seed germination and radicle elongation of the receiver species. The aerial part of the donor species was the main source of water soluble allelopathic potential compounds. Independently of the donor species, D. adscendens and S. rhombifolia were the weeds with the greatest sensibility to allelopathic potencial effects from donor species, while V. polyanthes showed more tolerance.
TL;DR: In this article, the authors present a review of the fate of allelopathy in the soil environment to help to find strategies to increase the activity of an allelhemical.
Abstract: SUMMARY Allelochemicals are compounds released by one plant or plant residues that may have a negative or positive effect on other plant. The importance of allelopathy was extensively explored during the past three decades, with the work concentrating in the extraction and identification of the chemicals, and demonstration of activity in petry dish experiments. These compounds interact in the soil environment similarly as herbicides and are subject to processes of degradation such as microbial degradation, oxidation, and photolysis, and processes of removal or transfer, such as volatilization and adsorption. The objective of this review was to access the fate of allelochemicals in the soil environment to help to find strategies to increase its activity. The activity of allelochemical is limited in time (because of slow release from the donor material) and in space (because of the interaction with the environment). Demonstration of allelopathy should include the fate of the proposed chemical in the soil environment, presenting studies of degradation and removal processes.
TL;DR: Germination in tomato and ryegrass was reduced by 30% when exposed to the highest concentration of unweathered kenaf, and germination and length of most plants increased, suggesting that, over time, the detrimental compounds in kanaf were leached or otherwise changed so that they had no effect or became beneficial.
TL;DR: The findings of this study suggest that choice of species and cultivar may be a valuable management option for minimising the negative effects of vulpia residues, and provides a simple and rapid screening methodology for assessing the relative tolerance of plant species to the allelopathic effects of weed residues.
Abstract: Summary. The germination and seedling growth of 12 plant species and 12 cultivars from 2 plant species were tested in the presence of aqueous extracts of vulpia dry matter residues. Concepts of whole-range assessment and inhibition index were developed, and used, with principal component analysis, for assessing results. Species were grouped according to the inhibition index. Average threshold concentration, average I50 (the extract concentration required to cause 50% inhibition in plant response) and average root and coleoptile lengths were used as auxillary indices for each group. Marked differences in tolerance toward the phytotoxicity of vulpia residue extracts were observed among species and cultivars. Such differences were widespread among plant species, with generally cocksfoot, Vulpia spp., subterranean clover (cv. Trikkala), phalaris, canola, medics, and oats being relatively tolerant, while lupins, barley, and wheat (cvv. Janz, Vulcan) were the most susceptible, and subterranean clover (cvv. Seaton Park, Karridale, Clare, Woogenellup, Junee), field peas, and wheat (cvv. Ford, Darter, Dollarbird, Rosella) were relatively susceptible. The findings of this study suggest that choice of species and cultivar may be a valuable management option for minimising the negative effects of vulpia residues. The whole-range assessment developed in this study proved to be a statistically efficient summary of the plant response profiles. Together with the bioassay techniques adopted, it provides a simple and rapid screening methodology for assessing the relative tolerance of plant species to the allelopathic effects of weed residues.
TL;DR: The results suggest that the allelochemicals from soil extracts, rather than pathogenic fungi, are the key factor regulating the productivity and nitrogen cycling in repeated plantation woodlands.
Abstract: Effects of soil extracts from repeated plantation woodlands of Chinese-fir on soil fungi growth, the activities of microbial communities, and rates of net soil nitrogen mineralization were investigated. Soil extracts from replanted woodlands significantly inhibited soil non-pathogenic fungi growth, reduced soil respiration activities, and net soil nitrogen mineralization rates. However, soil extracts from replanted woodland increased the growth of pathogenic fungi. The combination of soil extracts and pathogenic fungi did not significantly reduce the growth of Chinese-fir seedlings when compared to the soil extracts alone. The combination of soil extracts with pathogenic and non-pathogenic fungi significantly increased the growth of Chinese-fir seedlings when compared to the combination of soil extracts and pathogenic fungi. The results suggest that the allelochemicals from soil extracts, rather than pathogenic fungi, are the key factor regulating the productivity and nitrogen cycling in repeated plantation woodlands.
TL;DR: It was observed that aqueous extracts, rain leachates and litter from dried and fresh shoot and roots invariably inhibited the germination and seedling growth of both the crop species.
Abstract: Laboratory studies were conducted to see the allelopathic suppression of wheat and mustard byRumex dentatus ssp.klotzschianus (Meissn) Rech. It was observed that aqueous extracts, rain leachates and litter from dried and fresh shoot and roots invariably inhibited the germination and seedling growth of both the crop species. Soil collected from beneathRumex dentatus also proved harmful for the germination and seedling growth. It is suggested thatRumex dentatus ssp.klotzschianus exhibits allelopathy against wheat and mustard.
01 Feb 1997
TL;DR: In this paper, the authors investigated the allelopathic potential of rice in which rice had been grown with Echinochloa crus-galli in the field, and the results indicated that there are genetic differences among varieties for allelopathy potentiality on E. crusgalli.
Abstract: Rice (Oryza sativa L.) contains water-soluble substances that inhibit the germination of Echinochloa crus-galli. This study investigated the allelopathic potential of rice in which rice had been grown with E. crus-galli in the field. Extracts of forty-seven rice varieties were screened for allelopathic potential in the laboratory. Double distilled water was used as a control. Based on the germination percentage, the varieties may be classified in the following order of decreasing inhibition : Namweon(36%) and Gyehwa(38%) hulls extracts and Sambaeg(43%) and Seoan(46%) leaves extracts. In the comparison of allelopathic activity test between leaves and hulls extracts, hulls extracts contain more allelopathic toxic substances. In the effect of concentration treatment on the six levels of extract solutions(3, 6, 12, 25, 50, 100%, v/v) germination percentage was significantly inhibited as the extract concentration increased. The highest concentration(100%) caused the greatest reduction in E. crus-galli. Allelopathic potential effects were significantly different among the various varieties and between '94 and '95 year extracts. The results indicate that there are genetic differences among varieties for allelopathic potentiality on E. crus-galli. Allelopathic potential in the ecological aspects can be decided through variety selection.
TL;DR: This technique clarifies the occurrence of allelopathic interference by qort on seed germination and seedling growth, and hence suspects the allelopathy potential of qort in the growth reduction of associate species under field conditions along with competition.
Abstract: Indoor experiments demonstrated that allelopathic potential of rosette and flowering plants of qort is an important factor explaining the growth reduction of its associated species. Aqueous tissue extracts of flowering plants exhibited strong inhibitory effects on the germination percentage and radicle growth rate of the tested species as compared with those of vegetative plants. Under laboratory conditions, this inhibition was in agreement with toxicity assessments of soil samples collected from the rhizosphere of T. resupinatum L., where shoot and root dry mass of the tested species were significantly reduced. Detoxification of allelochemicals by presence of activated carbon can eliminate the inhibitory effects of the different extracts. This technique clarifies the occurrence of allelopathic interference by qort on seed germination and seedling growth, and hence suspects the allelopathic potential of qort in the growth reduction of associate species under field conditions along with competition.
TL;DR: In this paper, the authors investigated whether allelochemicals that could suppress other algae were released from the coralline red algae, Corallina pilulifera and Pneophyllum zostericolum.
Abstract: We investigated whether allelochemicals that could suppress other algae were released from the coralline red algae, Corallina pilulifera and Pneophyllum zostericolum. Bialgal cultures were composed of either of the two coralline species and Laminaria sporelings in a millicell-CM insert. Higher culture temperatures tended to increase suppressive activities of both coralline algae against female gametophyte maturation and normal sporophyte formation of Laminaria. Even if dissolved iron, which is known to be required for the gametophyte maturation, was amply supplied to PES medium, the suppressive activity was still recognized. In bialgal cultures, when C. pilulifera and L. japonica sporelings were horizontally placed, the suppressive activity decreased compared to those vertically placed. Suppressive effects against the female gametophyte maturation in the conditioned medium of C pilulifera was apparently lower than those in bialgal cultures. These results led us to assume that allelochemicals released from the coralline algae suppressed development of Laminaria sporelings and that they were volatile and/or labile substances. Three kinds of volatile halomethanes known to be released from C. pilulifera: bromoform, dibromochloromethane, and dibromomethane, were examined for suppressive effects on the development of L. angustata sporelings. Bromoform at a concentration as low as 3 ppm apparently reduced the normal sporphyte formation. Dibromochloromethane and dibromomethane showed weaker toxicities; both halomethanes contain less bromine atoms than bromoform. However, since we could detect only extremely low concentrations of bromoform in the cultures of C. pilulifera, we came to the conclusion that the actual allelochemicals in the bialgal cultures could not be the above halomethanes.
TL;DR: It is suggested that prior to formulating and recommending cyanobacterial inocula as biofertilizers, their allelopathic aspects should be studied to determine a soil to algae ratio ratio.
Abstract: Allelopathic effects of cyanobacterial inoculum on soil characteristics and cereal growth were investigated. Research established the alteration of chemical characteristics of the soils inoculated with different concentrations of cyanobacterial inoculum. Inoculated soils, compared with uninoculated soils, sometimes had significantly different values for chemical characteristics such as pH, electrical conductivity, organic matter, organic N, total phenolics, and exchangeable cations such as Cu, Zn, Na, K, Mg, and Ca as the level of inoculum increased. Despite a significant increase in organic nitrogen in the inoculated soils, root growth of rice and wheat was suppressed. The total phenolic content of inoculated soils increased in proportion to the concentration of inoculum added and the suppression of root growth. It is, therefore, suggested that prior to formulating and recommending cyanobacterial inocula as biofertilizers, their allelopathic aspects should be studied to determine a soil to algae ratio ha...
TL;DR: The straw leachate and various fungi had distinct impacts on the virulence of Colletotrichum sp.
Abstract: Allelopathy and endophytic fungi were evaluated as factors affecting the biological control of marsh reed grass, Calamagrostis canadensis (Michx.) Beauv., a weed of boreal reforestation areas. Leac...
01 Jan 1997
TL;DR: Differences in the inhibition and stimulation of the growth of the wheat rootlets were observed among both communities, and the possible influence of allelopathic effects on the coexistence of a particular mixture of plant species in a determined area is discussed.
Abstract: Phytotoxicity of aqueous extracts from 60 plant species from tropical and temperate communities was tested by wheat rootlet growth inhibition assay. Differences in the inhibition and stimulation of the growth of the wheat rootlets were observed among both communities. 26.7 % of the total sample belonging to the tropical community showed considerable allelopathic activity in this bioassay, while 23.3% of the total sample stimulated rootlet growth. On the other hand, 71.9% of the temperate plants studied presented this activity, while none of the species showed stimulating effects. The possible influence of allelopathic effects on the coexistence of a particular mixture of plant species in a determined area is discussed.
TL;DR: Using many bioassays produces the most conclusive evidence of allelopathic activity, and cell suspension growth was the most sensitive in in vitro culture, whereas callus culture was the least sensitive.
Abstract: Toxicity threshold levels for five different bioassays (germination in combination with radicle length, seedling growth, callus growth, plating, and cell suspension growth) were determined on three invasive arborescent species [American elm (Ulmus americana), red maple (Acer rubrum), and pin cherry (Prunus pensylvanica)] using two different mixtures of allelochemicals. Thresholds for the duckweed (Lemna minor) bioassay and lettuce (Lactuca sativa) seed germination bioassay were also determined for comparison with the same mixtures. All five bioassays showed a sensitivity similar to those of duckweed and lettuce bioassays. The lowest sensitivity was in mixtures containing about 5000 μg/liter of each chemical, but the species tested and the mixture applied influenced the outcome. Some bioassays could not be used with red maple (plating and cell suspension) and pin cherry (germination and seedling growth). Cell suspension growth was the most sensitive in in vitro culture, whereas callus culture was the least sensitive. Cell suspension growth in multiwell culture plates should be favored in allelopathy studies because of its sensitivity and the need for relatively small volumes of sample. Detection of phytotoxicity using whole plant systems (germination and seedling growth) and tissue culture appeared not to be directly correlated. We conclude that using many bioassays produces the most conclusive evidence of allelopathic activity.
TL;DR: Greenhouse studies were conducted to test allelopathic effects of Artemisia campestris ssp.
Abstract: Greenhouse studies were conducted to test allelopathic effects of Artemisia campestris ssp. caudata on seed germination and seedling growth of several sand-dune species and colonization by mycorrhizal fungi. The aqueous extracts of A. campestris showed no inhibitory effect on seed germination, seedling elongation, or dry-weight growth of plants at lower concentrations (10 and 50%), but 100% concentration of the extracts caused varying degrees of inhibition depending on the test species. The mixing of dry leaves of seedlings of A. campestris to the sand showed severe inhibition of Elymus canadensis seedlings. The percent germination of test species in soil from the rhizosphere of A. campestris was significantly lower than that of the control. The leaf area and dry weight were also lower but the differences were not significant. The aqueous extract inhibited mycorrhizal fungal colonization in roots of three sand-dune grasses. Key words: allelopathy, Artemisia campestris ssp. caudata, seed germination, seedl...
Journal Article•
TL;DR: The seasonal variations in the amount and the allelopathic potential of the water-soluble, leaf epicuticular exudates in the Mediterranean ruderal Dittrichia viscosa were investigated and confirmed the prediction that the seasonal fluctuations should be commensurate with the ascribed antitranspirant and phytotoxic functions.
Abstract: The seasonal variations in the amount and the allelopathic potential of the water-soluble, leaf epicuticular exudates in the Mediterranean ruderal Dittrichia viscosa were investigated. Both parameters peaked during the dry, hot, and sunny summer, confirming the prediction that the seasonal fluctuations should be commensurate with the ascribed antitranspirant and phytotoxic functions. In particular, the drainage of the material to the soil with the heavy autumn rains provides excellent timing for exerting its strong allelopathic interference on seed germination, affording D. viscosa a considerable competitive advantage. Key words: allelopathy, Dittrichia viscosa, leaf rinsates, seasonal variations.
Journal Article•
01 Jan 1997
TL;DR: It was observed that aqueous extracts, rain leachates and litter from dried and fresh shoot and roots invariably inhibited the germination and seedling growth of both the crop species.
Abstract: Laboratory studies were conducted to see the ailelopathic suppression of wheat and mustard by Rumex dentatus ssp. klotzschianus (Meissn) Rech. It was observed that aqueous extracts, rain leachates and litter from dried and fresh shoot and roots invariably inhibited the germination and seedling growth of both the crop species. Soil collected from beneath Rumex dentatus also proved harmful for the germination and seedling growth. It is suggested that
TL;DR: Experiments for assessing the allelopathic effects of C. album and C. polyspermum on three indicator species were conducted under controlled conditions, finding that sunflower and tomato are good indicators for their relative allelopathy.
Abstract: Chenopodium album L. and Chenopodium polyspermum L. are cosmopolitan weeds that often cause serious crop yield losses. Although it is well known that both species compete strongly with crops, nothing has been published on their relative allelopathic potentials. Experiments for assessing the allelopathic effects of C. album and C. polyspermum on three indicator species were conducted under controlled conditions. The indicator species were sunflower (Helianthus annuus L. cv. SO 222), tomato (Lycopersicon esculentum Mill cv. Heinz 1370) and the cosmopolitan weed Indian goosegrass (Eleusine indica subsp. indica (L.) Gaertn.). Top growth of mature C. album and C. polyspermum plants was freeze-dried, milled to a coarse powder and gamma-irradiated. Steam-sterilized soil was mixed with the powdered material to reach a concentration of 1% for each donor species. The control treatments consisted of an untreated soil and the same soil containing 1% extracted material of the donor species. Only sunflower and tomato s...