Showing papers on "Allelopathy published in 1994"

Separation of allelopathy and resource competition by the boreal dwarf shrub Empetrum hermaphroditum Hagerup

Abstract: An experimental technique was used to separate and evaluate the magnitude of allelopathic interference relative to resource competition by the boreal dwarf shrub Empetrum hermaphroditum Hagerup (Empetraceae). To test for resource competition and allelopathy, respectively, Scots pine (Pinus sylvestris L.) seedlings were grown in both the greenhouse and in the field over a 3 year period, in four different treatments within E. hermaphroditum vegetation: (1) PVC tubes were used to reduce effects of interspecific below-ground competition; (2) activated carbon was spread on the soil to adsorb toxins leached from E. hermaphroditum litter and green leaves, thus reducing effects of allelopathic interference; (3) E. hermaphroditum vegetation was left untreated to evaluate inhibiting effects when both allelopathy and resource competition were present; (4) PVC tubes, placed in E. hermaphroditum vegetation spread with activated carbon were used to determine growth of seedlings when both allelopathy and resource competition were reduced. Scots pine seedlings grown in untreated vegetation (with both root competition and allelopathy present) had the lowest shoot length and dry weight; seedlings with both allelopathy and root competition reduced (activated carbon in tube) were the largest. Reducing either root competition alone (tube treatment) or allelopathy alone (carbon treatment) produced seedlings of intermediate size, but reduced competition had a greater effect than reduced allelopathy (although, in the greenhouse, significantly so only for root biomass). In the greenhouse experiment, biomass production of seedlings grown free of both interactions (carbon in tube) was greater than the simple sum of the growth response to the individual interactions (tube treatment and carbon treatment, respectively). Larger shoot:root ratios were also found when pine seedlings were grown without tubes (i.e. when resource competition was occurring). In the field, the removal of allelopathy (carbon treatments) increased shoot:root ratio when compared to the removal of resource competition. The study showed that two different interference mechanisms of E. hermaphroditum can be separated and quantified, and that below-ground competition and allelopathy by E. hermaphroditum are both important factors retarding growth of Scots pine.

Allelopathy : organisms, processes, and applications

Abstract: Allelopathy - current status and future goals, Frank A. Einhellig. Part 1 Allelopathic interactions involving specific organisms: lichen allelopathy - a review, James D. Lawrey overcoming allelopathic growth inhibition by micorrhizal innoculation, A.U. Mallik and H. Zhu allelopathic herbaceous vascular hydrophytes, Stella D. Elakovich and Jean W. Wooten identification of allelochemicals in eucalyptus citriodora and polygonum sachalinense, Hiroyuki Nishimura and Junya Mizutani quercetin and quercitrin from pluchea lanceolata and their effect on growth of asparagus bean, Inderjit and K.M.M. Dakshini. Part 2 Processes in allelochemical action: mechanism of action of allelochemicals in allelopathy, Frank A. Einhellig allelopathic properties of alkaloids and other natural products - possible modes of action, M. Wink and B. Latz-Bruening the value of model plant-microbe-soil systems for understanding processes associated with allelopathic interaction - one example, Udo blum characterization of the mechanisms of allelopathy - modeling and experimental approaches, H.H. Cheng plant stress and allelopathy, Chung-Shih Tang et al chemical communication between the parasitic weed striga and its crop host - a new dimension in allelochemistry, Larry G. Butler. Part 3 Allelopathy in agroecosystems. Part 4 Biocontrol and applications of allelochemicals. (Part contents)

In search of allelopathy in the Florida scrub: The role of terpenoids.

Abstract: The hypothesis was tested that allelopathic agents released from fire-sensitive plants of the Florida scrub community deter the invasion of fireprone sandhill grasses. The structures of the constituents of four endemic scrub species,Conradina canescens, Calamintha ashei, Chrysoma pauciflosculosa, andCeratiola ericiodes, were established and their phytotoxic activity against two grasses of the sandhill was examined. Effects of the secondary metabolites from the above scrub species and their degradation products upon the germination and radicle growth of little bluestem (Schizachyrium scoparium) and green sprangletop (Leptochloa dubia), two native grasses of the Florida sandhill community, were determined. The studies included determination of the water solubility and release mechanism of terpenes and other allelopathic agents from the source plants and their aqueous transport to the target species. Some of the natural products were nontoxic until activated by light and/or oxidation after release from the source plant into the environment.

Effects of benzoic and cinnamic acids on growth, mineral composition, and chlorophyll content of soybean.

Abstract: Organic acids are major water-soluble allelochemicals found in soil infested with quackgrass and are involved in several processes that are important in plant growth and development. This study was carried out to gain more information on the effects of benzoic acid (BEN) andtrans-cinnamic acid (CIN) on growth, mineral composition, and chlorophyll content of soybean [Glycine max (L.) Merr. cv. Maple Bell] grown in nutrient solution. The two allelochemicals reduced root and shoot dry biomass of soybean. Treated plants had fewer lateral roots and tended to grow more horizontally compared to the untreated plants. Lateral roots were stunted and less flexible. The amounts of P, K, Mg, Mn, Cl−, and SO42− were lower, and Zn and Fe contents were higher in roots of plants grown with BEN or CIN as compared to untreated plants. Shoots of plants grown with the allelochemical showed greater accumulation of Ca, Mg, and Zn, whereas P and Fe contents were reduced. The BEN and CIN also caused reductions in leaf chlorophyll content. The BEN and CIN may be responsible for negative allelopathic effects of quackgrass on soybean by inhibiting root growth, by altering ion uptake and transport, and by reducing chlorophyll content.

Allelopathic effect of Pluchea lanceolata (Asteraceae) on characteristics of four soils and tomato and mustard growth

Abstract: The effect of the leachate of the noxious weed Pluchea lanceolata was explored using mustard and tomato seedling growth bioassays of four soil types (sandy loam, clay loam, silty loam, and sand). The objectives of the present study were: 1) to determine how soil chemistry changes after addition of leachate and leaves of the weed; 2) to determine what level of input to the soil does not cause significant differences from those of weed-associated soils under field conditions; and 3) to determine whether soil texture affects bioassay results. Leaf leachates of the weed were added to four soil types in different dilutions, and soils were analyzed for pH, electrical conductivity, organic matter, Cl, P04, exchangeable Cu++, Zn++, Na+, K+, Mg++, and Ca++, and total phenolics. These results indicated that the leachates of the weed altered chemical characteristics of each soil type. Concentration of phenolics in treatment of each soil type was dilution-dependent. Leachates were more inhibitory on sandy loam and clay loam than on silty loam and sand. Present study indicated that in allelopathic bioassays, amended soils that are nonsignificantly different from weed-associated soils should be taken. Further, present investigations confirmed the significance of good control soil with nonsignificantly altered chemical characteristics from those of natural soils, as well as soil texture to establish allelopathy of ecological relevance.

The effect of phytotoxins on competitive outcome in a model system

Abstract: The difficulty of distinguishing allelopathy from resource competition among plants has hindered investigations of the role of phytotoxic allelochemicals in plant communities. The effects of allelopathic substances on competitive outcome when two species differ in their sensitivity to an inhibitor were modelled by applying atrazine, a commonly used herbicide for broadleaf weeds, to corn—soybean mixtures. A target—neighbor design was used, in which differing densities of a neighbor species are planted around one individual of the target species. This design is particularly appropriate to investigations of allelopathy, due to the density—dependent nature of phytotoxic effects. Neighbor density greatly influenced the response to the toxin. At a corn densities of 0, 3, 6, 9, and 12 plants per pot and atrazine treatment of 3.0 mg/kg, the dry mass of the soybean (target) plant increased from 0.2 g with no neighbors to 0.5 g with 9—12 neighboring corn plants. The increased growth of soybean at higher corn densities is contrary to the predicted effects of resource competition and is due to uptake of atrazine by the corn plants, which decreased the amount available to the soybean target. Detoxification of soil by neighbors may explain in part the conflicting assessments of some putatively allelopathic species, such as black walnut (Juglans nigra).

Algal allelopathy

Abstract: The comprehensive review on allelopathy (Rice, 1979, 1984) has been largely responsible for the evolution of allelopathy as an independent branch of chemical/ physiological ecology. The allelopathic research during the last four decades drew attention to different facets of the interactions among the constituents of habitat, calling for an understanding of the role of allelopathy under different habitat conditions. In view of this, we have reviewed the existing information on allelopathic interactions in aquatic habitats with special reference to algal allelopathy. This review has been mainly confined, therefore, to different aspects of algal allelopathy such as allelopathic interactions in algae, algal toxins, bioassays, and implications of algal allelopathy.

Allelopathic Characteristics of Three Cool-Season Grass Species in the Forage Ecosystem

Abstract: Allelopathy, the direct or indirect effect of one plant on another through the production of chemical compounds that escape into the environment, occurs widely in natural plant communities and is postulated to be one mechanism by witch weeds interfere with crop growth. The purpose of this research was to determine the potential allelopathic influence of selected cool-season grass species on species interseeded into the pasture ecosystem. Aqueous extracts of tall fescue (Festuca arundinacea Schreb.), Italian ryegrass (Lolium multiflorum Lam.), and little barley [Critesion pusillum (Nutt.) A. Love; syn. Hordeum pusillum Nutt.] leaf and stem tissue harvested at the mature stage of plant development reduced seed germination and seedling growth of alfalfa (Medicago sativa L.) and Italian ryegrass [...]

Allelopathic potential of vegetative and flowering ragwort (Senecio jacobaea L.) plants against associated pasture species

Abstract: The allelopathic effects of vegetative and flowering plants of the annual/biennial pasture weed Senecio jacobaea L. (ragwort) against Lolium perenne L. (perennial ryegrass) and four pasture legumes were investigated using a range of bioassays. Bioassays based on shoot and root leachates demonstrated detectable, although usually slight, allelopathic effects, and these did not usually differ between the two developmental stages of S. jacobaea. However, aqueous extract and tissue decomposition bioassays demonstrated stronger allelopathic effects, particularly for flowering plants, and this was in general agreement with toxicity assessments of soil collected from under S. jacobaea plants in the field. According to our study, flowering plants have the potential to weaken pasture through allelopathy, and decomposition of above-ground litter appears as the most likely mechanism facilitating this. The aqueous extract and tissue decomposition bioassays also revealed that L. perenne was less susceptible to S. jacobaea allelopathy than were the legumes, suggesting that encouraging a strong L. perenne component in pastures has potential for reducing the overall inhibitory ef S. jacobaea on pasture production.

Allelopathy of oats. I. Assessment of allelopathic potential of extract of oat shoots and identification of an allelochemical.

Abstract: The allelopathic potential of oat (Avena sativa L.) extracts was investigated under laboratory conditions. The ethyl ether-, acetone-, and water-soluble fractions obtained from the extract of oat shoots inhibited the germination and growth of roots and hypocotyls of lettuce (Lactuca sativa L.). The inhibitory activity of the water-soluble fraction was maximum, followed by that of ethyl ether-soluble and acetone-soluble fraction. An active principle of the water-soluble fraction was isolated and its structure was determined by spectral data asl-tryptophan.l-Tryptophan inhibited the growth of hypocotyls and roots of lettuce seedlings at concentrations greater than 0.03 and 0.1 mM, respectively. These results suggested thatl-tryptophan may be an allelochemical which affects the growth or germination of different plant species.

Exhibition of allelopathy by Parthenium hysterophorus L. in Agroecosystems

Abstract: The yield and biomass of five pulse crops namely, Cyamopsis tetragonoloba, Phaseolus aureus, Phaseolus mungo vars. MI-1 Pantu-19 and Vigna umbellata when grown in soil earlier infested with Parthenium hysterophorus were greatly reduced. The seed germination parameters and relative growth rate of the crops were also reduced. The soil inhabited with P. hysterophorus was not rendered poor in its available macronutrients especially nitrogen, phosphorus and potassium. On the contrary, it was enriched. However, the texture, pH and conductivity of the P. hysterophorus inhabited soil were almost the same as that of the control (about 100 m away). On the other hand, the amount of soil chemicals was found to be maximum in P. hysterophorus inhabited soil sampled from all the three depths (0-7, 14-21 and 28-35 cm depths), compared to respective soil layers from the control. The bio-efficacy studies of the soil chemicals conducted on a representative plant Phaseolus aureus, points to its inhibitory nature. Not only the different germination parameters were affected but the mature plants too showed reduced cell survival, contents of water and chlorophyll compared to the control. Thus, the chemicals accumulated in the soil infested with P. hysterophorus, qualify to be called as allelochemicals.

Allelopathic potential of the phenolics from the roots of Pluchea lanceolata [chlorogenic acid, formononetin, 7-O-glucoside, phloroglucinol]

Abstract: Aqueous leachates of roots of the perennial weed Pluchea lanceolata (DC.) C. B. Clarke, its root-incorporated soil and rhizosphere soil, interfered with the seedling growth of certain plant species. The soils from the rhizosphere zone of this plant had significantly higher total phenolics and HPLC analysis revealed that phenolic fractions represented by retention times of 1.6, 1.9, 2.5 (simple phenol, chlorogenic acid and phloroglucinol respectively), 3.7 and 4.3 min were contributed by roots of the weed to the soil. The phenolic fraction represented by the retention time 3.3 (formononetin 7-O-glucoside) was detected in the weed's rhizosphere soils and not in the rootincorporated soils. UV spectral studies established the presence of phloroglucinol, simple phenol, chlorogenic acid, formononetin 7-O-glucoside, and methylated coumarins in the root leachate, which affect the seedling growth of mustard (Brassica juncea). Present research established the allelopathic potential of P. lanceolata roots, and the possible involvement of allelopathy in its interference success.

Potential allelochemicals fromRuta graveolens L. and their action on radish seeds

Abstract: An aqueous extract ofRuta graveolens L. (250 g/liter) was tested for its allelopathic activity in vitro on radish germination and radicle growth in light and darkness. It caused a delay in the onset and a decrease in the rate of germination (40%) in the light. The photoinhibition of germination was accompanied by an inhibition of water uptake into the seed. Furthermore, the inhibition of radicle growth was slightly higher in the light than in darkness. Three potential allelochemicals, biologically active in the light, were isolated from the extract: 5-methoxypsoralen (5-MOP), 8-methoxypsoralen (8-MOP), and 4-hydroxy-coumarin at concentrations of 10−4 M, 2×10−4 M, and 0.4 ×10−5 M respectively. At a concentration of 2×10−4 M, 5-MOP was the most potent inhibitor, decreasing radish germination to 32% and radicle growth to 17% with respect to control. Microscopic observations of radish seeds treated with 5-MOP suggest that this substance changes the swelling of the seed coat and aleurone layer, which precedes radicle protrusion.

Allelopathic potential of the phenolics from the roots of Pluchea lanceolata

Abstract: Aqueous leachates of roots of the perennial weed Pluchea lanceolata (DC.) C. B. Clarke, its root-incorporated soil and rhizosphere soil, interfered with the seedling growth of certain plant species. The soils from the rhizosphere zone of this plant had significantly higher total phenolics and HPLC analysis revealed that phenolic fractions represented by retention times of 1.6, 1.9, 2.5 (simple phenol, chlorogenic acid and phloroglucinol respectively), 3.7 and 4.3 min were contributed by roots of the weed to the soil. The phenolic fraction represented by the retention time 3.3 (formononetin 7-O-glucoside) was detected in the weed's rhizosphere soils and not in the rootincorporated soils. UV spectral studies established the presence of phloroglucinol, simple phenol, chlorogenic acid, formononetin 7-O-glucoside, and methylated coumarins in the root leachate, which affect the seedling growth of mustard (Brassica juncea). Present research established the allelopathic potential of P. lanceolata roots, and the possible involvement of allelopathy in its interference success.

Comparison of the insecticidal effects of water extracted and intact aromatic plants onAcanthoscelides obtectus, a bruchid beetle pest of kidney beans

Abstract: Acanthoscelides obtectus (Say) is one of the most damaging pests of kidney beans,Phaseolus vulgaris L. worldwide. However, aromatic plants from the families Lamiaceae, Lauraceae, Myrtaceae and Poaceae can protect kidney beans by direct or delayed insecticidal effect, through increased adult mortality and inhibition of beetle reproduction (both oviposition and adult emergence). The efficiency of hydrodistillated and intact plants fromThymus vulgaris andT. serpyllum, Mentha piperata, Rosmarinus officinalis, Satureia hortensis, Eucalyptus globulus, Laurus nobilis, Origanum vulgare, andCymbopogon nardus was compared. For both extracts,Origanum vulgare had the best effect. The insecticidal effect was induced by more than the essential oils because no significant difference was noticed between distilled and intact plants extract. Inhibition of reproduction was particularly important. These results suggest that lipidic as well as non lipidic, allelochemicals, such as phenolics, or non-protein amino-acids, or flavonoids may be involved in the toxicity of aromatic plants to this beetle.

Study on the Allelopathy of Alfalfa (Medicago sativa L.): II. Isolation and identification of allelopathic substances in alfalfa

Abstract: Allelopathic substances in alfalfa plants (Medicago sativa L.) were purified from methanol extracts of alfalfa shoots. The methanol extracts were fractionated into an acidic fraction, and the sample was divided into 10 fractions by thinlayer chromatography (TLC). Growth of radish seedlings was inhibited by the substances obtained from Rf values of 0.5∼0.6 and 0.6∼0.7. These fractions were eluted with distilled water, and the eluates were analyzed by high-performance liquid chromatography (HPLC). Six peaks were detected on the chromatogram. Growth of radish seedlings was inhibited on three peaks. Of these peaks, two were identified using HPLC, a mass-spectrometer, IR, and 1NMR as follows : peak b, ferulic acid and peak f, salicylic acid. The growth of alfalfa and radish seedlings was inhibited at lower concentrations of these substances.

Simultaneous effects of potassium, rutin and temperature on performance of Manduca sexta caterpillars

Abstract: The simultaneous effects on an insect herbivore (third instar tobacco hornworm Manduca sexta (L.): Sphingidae) of temperature (daytime temperatures of 20 °C, 25 °C and 30 °C), a mineral that may play a role in plant defense (potassium) and a common allelochemical (rutin) were examined in a factorial experiment. To manipulate potassium levels, a modified diet with limited plant material was used as the base and KCl and rutin added. Temperature affected efficiency of conversion of ingested food (ECI), efficiency of conversion of digested food (ECD), time to head-capsule slippage, stadium duration, relative consumption rate (RCR) and relative growth rate (RGR) but not food consumed, biomass gained and approximate digestibility (AD). Potassium concentration influenced all of the variables except AD, time to head-capsule slippage (HCS), duration of the stadium and percent of stadium time to HCS. Rutin impacted negatively on all of the variables except food consumed. Compared to larvae on the non-rutin diets, fewer larvae fed rutin survived through molt initiation to ecdysis and fewer successfully completed ecdysis. Temperature and rutin had interactive effects for AD, ECD, RCR, RGR, time to HCS, and percent of stadium required to reach HCS. Rutin and potassium had interactive effects for biomass gained, RCR, ECI, time to HCS, duration of stadium, and percent of stadium required to reach HCS. Comparison of larval responses on an average potassium concentration (3.1%) versus high concentration (6.1%) showed that at the low daytime temperature increasing potassium concentration depressed biomass gained, but at the warmer temperatures potassium concentration had little effect unless rutin was present. In addition, potassium concentration had little impact on ECI unless rutin was present. These results indicate that significant interactive effects occur among temperature, potassium and rutin, and thus suggest that such interactive effects on larval performance may be common under field conditions, which are characterized by varying temperature and different concentrations of minerals and allelochemicals in hostplants.

Effects of Several Commercial Plant Growth Regulator Formulations on Yield and Allelochemicals of Cotton (Gossypium hirsutum L.)

Abstract: In recent years, a number of kinetin-based commercial plant growth regulators have been evaluated for their effects on various crop plants. In a study at Mississippi State during 1986-1992, five commercial plant growth regulators and urea were evaluated as foliar sprays on growing cotton (Gossypium hirsutum L.) plants for their effects on yield, agronomic traits, and pest allelochemicals. Of the five tested, the activities of three (Burst, Foliar Triggrr, and Maxon) were attributed by their providers to cytokinins. FPG-5 contained cytokinins, IAA, GA, and several inorganic micronutrients, and PG-IV contained IBA, GA, and micronutrients, but no cytokinins. FPG-5 and Foliar Triggrr caused statistically significant increases in yield, but only in 1992. The foliar application of urea had a consistently negative effect on yield (...)

Identification of a plant growth inhibiting iridoid lactone fromDuroia hirsuta, the allelopathic tree of the ‘Devil's Garden’

Abstract: Bioactivity-directed fractionation of a root extract ofDuroia hirsuta (Rubiaceae), a toxic and potentially allelopathic understory tree from the western Amazon, has led to the isolation of the tetracyclic iridoid lactone, plumericin (1). Bioassays showing plumericin strongly inhibited lettuce radicle elongation at a concentration (IC50) of 35.8 μm/ml (123 μM). The isolation of a highly potent inhibitor of plant growth fromDuroia hirsuta supports the hypothesis that the lack of vegetation surrounding this tree is the result of allelopathy.

Allelopathic interaction between Chenopodium album L. and certain crop species

Abstract: Laboratory and glasshouse studies were conducted to assess the allelopathic effect of Chenopodium album L. on the germination and early growth of certain crop species. Test species were grown in soils containing 1% (m/m) freeze-dried shoot material of the weed. Aqueous extracts of soils containing weed residues and organic solvent extracts of shoots of the weed were tested for effects on the germination of certain crop species. Radish (Raphanus sativus L.) was the only crop not affected by the weed residue in the soil. Growth inhibition was 68% for cucumber (Cucumis sativus L.), 85% for onion (Allium cepa L.), 47% for tomato (Lycopersicon esculentum L.) and 51% for sunflower (Helianthus annuus L.). Except for radish and sunflower, stand loss contributed to reductions in growth. Germination of crop species was not affected by aqueous extracts of soil portions (100g) from soil either grown with the weed (residues later removed by sieving) or containing shoot material of the weed. In fact, the growth of radi...

Allelopathic effect of sorghum extract and residues on selected crops and weeds.

Abstract: To better understand the allelopathic effect of sorghum(Sorghum vulgare L.), the inhibitory activities of water extracts of the stem, leaf and root, and of residues of the stem to major crops and weeds associated with them were evaluated. The allelopathic activity of sorghum plants was species specific, and depended on source and concentration. Germination, and shoot and root length of all test species were inhibited by the different concentrations of the stem extract. Among the crop species, radish showed the most inhibition, followed by wheat and rice. Maize was the least sensitive species. Of the weed species, Ipomoea triloba was most inhibited, followed by Echinochloa colona and Rottboellia cochinchinensis. The water extracts of leaves, stems, and roots significantly inhibited germination and seedling growth in E. colona and radish. The stem extract gave the greatest inhibitory effect on E. colona while all three extracts produced similar response in radish. In the greenhouse trial, sorghum stem residue placed on the soil surface as mulch significantly inhibited seedling growth in E. colona and radish, but not that in rice.