Showing papers on "Allelopathy published in 1987"

Allelopathy in agroecosystems: Wheat phytotoxicity and its possible roles in crop rotation

Abstract: The germination rates of cotton and wheat seeds were significantly affected by various extracts of wheat mulch and soils collected from the wheat field This toxicity was even more pronounced against seedling growth Five allelochemics: ferulic,p-coumaric,p-OH benzoic, syringic, and vanillic acids, were identified from the wheat mulch and its associated soil Quantitatively, ferulic acid was found at higher concentrations thanp-coumaric acid in the soil Various concentrations of ferulic andp-coumaric acids were toxic to the growth of radish in a bioassay The functional aspects of allelochemic transfer from decaying residue to soil and the subsequent microbial degradation within agroecosystems are discussed, particularly as they relate to wheat crop rotation, with wheat and cotton, in Pakistan

Allelopathic effects of volatiles from some Cruciferae species on lettuce, barnyard grass and wheat growth

Abstract: Exposure of germinating seeds of lettuce, barnyard grass and wheat to volatile substances released from pulverised leaves of some Cruciferae species resulted in delay of germination and reduction of overall growth.B. juncea andB. nigra volatiles were the most damaging to all of the tested species. It is suggested that degradation products of glucosinolates occuring in cruciferous plants caused this allelopathic action.

The allelopathic potential of alfalfa root medicagenic acid glycosides and their fate in soil environments

Abstract: The allelopathic effect of alfalfa (Medicago media Pers.) and red clover (Trifolium pratense L.) root saponins on winter wheat seedling growth and the fate of these chemicals in soil environments were studied. Seed germination, seedling and test fungus growth were suppressed by water and by alcohol extracts of alfalfa roots, and by crude saponins of alfalfa roots, indicating that medicagenic acid glycosides are the inhibitor. Powdered alfalfa roots inhibited wheat seedling growth when added to sand. At concentrations as low as 0.25% (w/w) the root system was completely destroyed whereas seedling shoots suffered little damage. Red clover roots caused some wheat growth inhibition when incorporated to sand, but their effect was much lower than in the alfalfa root treatment.

Microsomal oxidation of allelochemicals in generalist (Spodoptera frugiperda) and semispecialist (Anticarsia gemmatalis) insect

Abstract: Midgut microsomes prepared from larvae of the fall armyworm [Spodoptera frugiperda (J.E Smith)], a generalist insect, and the velvetbean caterpillar (Anticarsia gemmatalis Hubner), a semispecialist, were used to study their oxidative activity toward a variety of allelochemicals. Allelochemicals such as terpenoids, alkaloids, indoles, glucosinolates, flavonoids, coumarins, cardenolides, phenylpropenes, and a ketohydrocarbon were all metabolized by the microsomal cytochrome P-450 monooxygenases in both species. Fall armyworm microsomes oxidized monoterpenes more favorably than other types of terpenes, indicating a preference for these compounds. In all instances, the oxidative metabolism of these allelochemicals can be induced by dietary allelochemicals such as indole 3-carbinol, indole 3-acetonitrile, menthol, flavone, or peppermint oil ranging from 1.3- to 9.5-fold. In the case of certain triterpenes, tetraterpene, alkaloid, coumarin, and cardenolides, metabolic activity can only be observed after induction. The monooxygenase activities toward these allelochemicals were generally higher in the generalist than in the semispecialist. These findings provide strong evidence that microsomal monooxygenases play an important role in the detoxification of plant toxins and hence host-plant selections in herbivorous insects.

Allelochemistry in marine macroalgae

Abstract: Allelochemistry refers to the effect of an organic compound released from one organism upon an organism separated from its source. When the donor and receptor are plants (or microorganisms placed in the plant kingdom), allelopathy is described whether the effect is harmful or beneficial. In the aquatic environment, water disperses any water‐soluble allelochemical from its point of release, and rapid dilution along with lack of contact between competing organisms reduces potential encounter. This review centers on macroalgae as the source of allelochemicals. In all examples, the releasor organism is a macroalga, but receptor organisms include algae, invertebrates, fish, and microbes. Direct evidence in the sea is scanty, and there is a need for appropriate experiments in the laboratory and field. The compounds that are released by macrolagae (e.g., polyphenolics, halogenated phenols, and terpenoids) may be fortuitous byproducts of metabolism. But where they alter colonization, growth, or reproduction in a ...

Studies on the allelopathic effects of some agroforestry tree crops

Abstract: SUMMARY The allelopathic influence of Eucalyptus tereticornis, Casuarina equisetifolia and Leuceana leucocephala was tested by growing crops of sorghum, cowpea and sunflower on topsoil and rhizosphere soil from plantations of those trees or on field soil either mulched with dry leaves or irrigated with aqueous leaf extracts. Crop germination, root length and dry matter production were depressed. Maximum reductions were obtained with top soil and by the effect of eucalyptus. Sorghum proved most susceptible to these influences.

Allelopathic effect of lantana on some agronomic crops and weeds

Abstract: The allelopathic effects of dried lantana shoot residues was examined on wheat, corn, soybean, Virginia pepperweed and velvetleaf on growth over a 30-day period. Significant differences in the growth of the test species were observed. Corn was the most sensitive and wheat was least affected by lantana residues. The other three species were intermediate in their growth response to lantana. Shoot lengths were affected in corn and velvetleaf while root length was reduced in all species except wheat. The shoot dry weights of wheat and soybean were not reduced by lantana residues. In the other three species there was a significant reduction of shoot dry weight due to lantana. The root dry weights of all the five species were reduced by lantana residue. The results demonstrated an overall rate dependent response of the plant species to lantana shoot residue concentrations.

Perspectives on allelopathy in mexican traditional agroecosystems: A case study in tlaxcala

Abstract: Agroecosystems in Tlaxcala, Mexico, are surrounded by trees and water channels and have a great variety of cultivated and noncultivated plants. The main results of a study carried out on a traditional agroecosystem in Santa Ines, Tlaxcala are presented. Some ecological aspects of polycultures, plant covers (dry leaves ofAlnus firmifolia, Berula erecta, andJuncus sp.), and the allelopathic potential of crops and noncultivated plants (fresh and dry material) were analyzed. The main plants (trees, shrubs, and herbs) present in the agroecosystem were identified. The total number of weeds in plots where plant covers were added was reduced. The number of nodules ofRhizobium phaseoli and the production of bean and squash increased with plant covers. Corn, beans, and squash showed a clear allelopathic effect, as well asChenopodium murale, Tradescantia crassifolia, Melilotus indicus, andAmaranthus hybridus, among other weeds. The contribution of allelopathy in studies of traditional agroecosystems is of great importance for the management of species in space and time. Allelopathy can be the basis of biological control of pests and weeds and of the discovery of new useful substances.

Autotoxicity of ragweed parthenium (Parthenium hysterophorus)

Abstract: Ragweed Parthenium (Partbenium hysterophorus L. #3 PTNHY) was found to exhibit autotoxicity. The active principle(s) were isolated from two parts of the plant using polar system. Principle(s) from the inflorescence were more effective than from the leaves. Leachates derived from the plant decreased percent cell survival and chlorophyll content. Leachates from leaves were more toxic to ragweed parthenium when applied to the foliage than when applied through the roots. The polar allelochemicals were highly effective in preventing rooting and sprouting of stem cutting and in reducing the regeneration potential of mature ragweed parthenium plants. Additional index words. Allelopathy, chlorophyll content, cell survival, rooting, PTNHY.

The selective allelopathic interaction of a pasture-forest intercropping in Taiwan

Abstract: An allelopathic interaction of a pasture-forest intercropping system was evaluated by experiments conducted in field and by laboratory assays. A study site was situated in the farm of Hoshe Forestry Experiment Station at Nantou County, Taiwan. After deforestation of Chinese fir (Cunninghamia lanceolata), a split plot design of 4 treatments, namely litter removed, litter removed and kikuyu grass (Pennisetum clandestinum) planted, litter left, and litter left and grass planted, was composed. Field meaurements showed that the fir litter left on the ground did not significantly inhibit the growth of weeds, kikuyu grass, and fir seedlings in the first four months following deforestation, while kikuyu grass significantly suppressed the growth of weeds longer than four months but did not reduce growth of fir seedlings. The aqueous extracts of fresh fir leaves, fir litter, and kikuyu leaves were bioassayed by using lettuce and rice seeds and stolon cuttings ofBrachiaria mutica. Bioassays showed that fresh fir leaves produced significant phytotoxicity while fir litter and kikuyu grass gave limited toxicity. Nine phytotoxic phenolics and many unidentified flavonoids were found in the leaf and litter of Chinese fir and kikuyu leaves. A good correlation between the degree of phytotoxicity and phytotoxins was obtained, indicating an allelopathy was involved. This finding suggests that allelopathy may contribute benefits in the intercropping system to reduce the need for herbicides and to lessen the labor cost for weed control.

Phytotoxic exudates from velvetleaf (abutilon theophrasti) glandular trichomes

Abstract: Nonvolatile exudates from velvetleaf glandular trichomes inhibited root and shoot growth of several weed and crop species in petri plate bioassays, but had no effect on seed germination per se. The exudate was efficiently collected by wiping both the stems and petioles with cotton swabs or by leaching with water, but was absent on the leaves ofvelvetleafplants. Cress (Lepidium sativum L.) was the most sensitive indicator species. Four types of trichomes appeared on the stem surface as revealed by scanning electron microscopy. Water soluble globules on the apices of 12to 15-celled glandular trichomes recurred and demonstrated their original potency within eight days after removal with cotton swabs. Both the quantity and phytotoxicity of the exudates from velvetleafplants cultured under varying environmental conditions were determined. While total exudate production was not affected at 16, 24, or 36 C, the exudates from plants cultured at 24 and 36 C were about twice as toxic as the exudate collected from plants grown at the lower temperature. Water stress decreased the amount of exudate collected, but the phytotoxic activity was increased by approximately the same factor. SECONDARY PLANT PRODUCTS are diverse in structure and distribution throughout the plant kingdom and have no obvious function in primary metabolism (Swain, 1977). Implicated in the defensive and protective mechanisms of plants, these secondary metabolites may have numerous ecological roles (Seigler, 1977; Swain, 1977; Lovett, 1982). They are released through volatilization, exudation, leaching or decomposition of plant residues. Some may act as allelochemicals which help plants defend against herbivores, insects, or neighboring plants. In addition to genetic differences, factors such as temperature, light quality and intensity, mineral deficiencies, age of plant, pathogens and predators, and water stress have been shown to affect the production of secondary compounds (Swain, 1977; Rice, 1984). The plasticity of secondary product formation in response to stress may aid in plant adaptation and survival. A variety of secondary compounds with biological activity are localized in or secreted from specialized plant structures called trichomes. Glandular trichome exudates from mite-resistant geraniums (Pelargonium hor' Received for publication 22 April 1986; revision accepted 5 September 1986. Journal Article No. 11930 of the Michigan Agricultural Experiment Station. 2Current address is Department of Agronomy, University of Wisconsin, Madison, WI 53706; Department of Horticulture and Landscape Architecture, University of Kentucky, Lexington, KY 40536; Pesticide Research Center, Michigan State University, East Lansing, MI 48824. We wish to thank Dr. Ingert Kuzych for assistance with the SEM studies. torum) contained two anacardic acid derivatives, o-pentadecenylsalicylic acid and o-heptadecenylsalicylic acid (Gerhold, Craig and Mumma, 1984). These compounds were moderately toxic when bioassayed with the twospotted spider mite, Tetranychus urticae. The aphid alarm pheromone, (E)-o-farnesene, was present in substantial quantities in air around wild potato (Solanum berhaultii) foliage (Gibson and Pickett, 1983). It was demonstrated that this chemical, which was secreted from leaf trichomes, induced rapid dispersal of settled aphid colonies. Green peach aphids (Myzus persicae) are killed by contact with secretions from the trichomes of several Nicotiana species (Thurston, Smith and Cooper, 1966). These secretions contain alkaloids, of which nicotine is the major constituent. Isoprenoids (mono-, sesqui-, and diterpenes) are also metabolites commonly found in the trichomes of flowering plants (Kelsey, Reynolds and Rodriguez, 1984). Some secondary compounds released from trichomes have also been implicated in allelopathy (Seigler, 1977; Swain, 1977; Lovett, 1982), the stimulatory or inhibitory effects that chemicals produced by one plant may exert on another (Rice, 1984). For example, the leaves of Artemisia absinthium bear glandular hairs which excrete ethereal oils and the alkaloid, absinthin (Funke, 1943). Plants in close proximity to A. absinthium have reduced vigor which has been attributed primarily to absinthin, which washes off the Artemisia plants onto the neighboring species. The glandular trichomes of Primula obonica secrete a phy-

Allelopathic effects ofChrysanthemum morifolium on germination and growth of several herbaceous plants.

Abstract: Aqueous extracts obtained from young green tops ofChrysanthemum morifolium inhibited the germination of six flowering plants, including chrysanthemum itself, provided for experiments. The same phenomenon was also clearly observed when powder made from young green tops and old leaves of chrysanthemum was used. Moreover, the growth of seedlings planted again in garden soil which was once used for the culture of chrysanthemum was greatly interrupted. Chrysanthemum cultured in used garden soil showed far less dry weight than that cultured in fresh garden soil. The weight of chrysanthemum cultured using its root exudates was also less than that cultured with water leachate of fresh garden soil, and therefore these results may be considered to indicate allelopathic effects. In order to find the allelochemicals related to this phenomenon, benzoic acid and phenolic acids such as salicylic,p-hydroxybenzoic, vanillic, gentisic, protocatechuic, syringic, gallic, ferulic, and caffeic acids were identified by gas chromatography.

Allelopathic effects of interrupted fern on northern red, oak seedlings: amelioration by Suillus luteus L.: Fr.

Abstract: The allelopathic effects of interrupted fern frond leachates on ectomycorrhizal (inoculated) and nonmycorrhizal (noninoculated) northern red oak (Quercus rubra L.) seedlings were investigated. Container-grown northern red oak was inoculated with vegetative mycelium ofSuillus luteus L. Fr. following acorn germination. Noninoculated control seedlings were also maintained. Seedlings were grown in a glasshouse under full sunlight or shaded (25% of full sunlight) conditions. Leachate or deionized water solutions were applied to seedlings eleven times over a 91-day period to simulate a rainfall induced transfer of allelopathic chemicals from fern fronds to the soil. Fern frond leachates significantly reduced seedling survival, however, inoculated seedlings showed less mortality. Chromium concentrations of pooled lateral root or leaf tissue were comparatively higher in tissues exhibiting greater mortality. Root biomass was reduced by fern fern frond leachate applications. Seedling biomass was not significantly affected by fungal inoculation. Our results confirm previous documentation of the allelopathic potential of ferns, and suggest that ectomycorrhizal fungi may ameliorate allelopathic effects of ferns on northern red oak seedling survival and growth.

Allelopathic effects of kochia on blue grama.

Abstract: The allelopathic effects of kochia aqueous extntcts found in kochir (Kochia scoparia L. Roth.) on seed germination and seedling growth of blue grama (Boutelouagracilis [H.B.K.] Lag.) were studied in Inboratory experiments. Extracts were from regrowth, whole tops, leaves, and stems, representing the vegetative and reproductive phenologies. Inhibition of seed germination did not occur. However, seedling radicle and shoot growth were significantly (PCO.05) affected. Inhibition declined significantly with concentrations of the solutions and advancing phenological stage. Similarly, hot water extracts inhibited growth more than cold water extracts. The data suggest possible inhibitory effects of kochia litter under field conditions, but detailed studies are lacking.

Allelopathy in the New Zealand grassland/pasture ecosystem

Abstract: The research (performed both locally and abroad) on the allelopathic potential of most common New Zealand pasture plants (including important weeds) is reviewed. The bioassay techniques usually used for demonstrating allelopathic influences have several drawbacks, often making the observed inhibitory effect of the donor plant a possible artefact of the method used. Other criteria required for the demonstration of allelopathy in the field have been sparingly satisfied, including the chemical identification of toxins, demonstration of concentration of toxins in the field, and the elimination of other possible factors explaining interference in the field. It is concluded that, to unequivocally prove allelopathy, one must first demonstrate that toxins from one plant are taken up by neighbouring plants and produce an inhibitory response. Studies of interference phenomena (including allelopathy) between plants in pastures might be potentially useful for weed control, or for determining mutual compatibi...

Allelopathic Effects in the Maize‐Quelites‐Agroecosystem of the Tarahumara Indians

Abstract: The Tarahumara Indians of the north-west Mexican Highland practice a method of using several weeds for food which are called “quelites”. These weeds play an important role in the Tarahumara diet and seem to be connected with maize-cultivation in a special way. In bio-assays with two quelites species, Bidens pilosa sens. lat. (Cobblers' pegs) and Lepidium virginicum (Pepper grass) and different cultivars of maize (Zea mays L.) it could be demonstrated that water extracts of leaves of B. pilosa and L. virginicum cause a significant stimulation of seedling growth of maize. Different cultivars of maize showed no differences in being stimulated by extracts of B. pilosa. This indicates an allelopathic potential of the two tested quelites species. Extracts of leaves of older plants of B. pilosa (shortly before flowering) do not show this effect. Different water extracts of maize snowed an indifferent influence on germination and seedling growth of B. pilosa and L. virginicum. Considering these results the practice of the Tarahumara Indians — leaving the quelites a certain amount of time among their maize and harvesting them after that — appears to be a stimulatory method for growing maize. The maize-quelites double-crop system seems to be highly tuned and may be understood as a result of a process of cultural learning among the Tarahumara Indians.