Showing papers on "Allelopathy published in 1992"

Allelopathy : Basic and applied aspects

Abstract: A discipline called allelopathy - S J H Rizvi, H Haque, V K Singh, and V Rizvi Allelopathy: broadening the context - J Lovett and M Ryuntyu A conceptual framework for assessing allelochemicals in the soil environment - H H Cheng Allelopathic effects on nitrogen cycling - E L Rice Allelopathic mechanism in fire prone communities - G B Williamson, D R Richardson and N H Fischer Allelopathic effects of cruciferous plants in crop rotation - A M Grodzinsky Improving yield of corn-soybean rotation: role of allelopathy - E Sarobol and I C Anderson Biochemical selection of sorghum crop varieties resistant to sorghum shoot fly (Atherigona soccata) and stem borer (Chilo partellus): Role of allelochemicals - H Alborn, G Stenhagen and K Leuschner Allelochemicals in wheat and barley: role in plant-insect interactions - L J Corcuera, V H Argandona and G E Zuniga Allelochemical properties of alkaloids: effects on plants, bacteria and protein biosynthesis - M Wink and T Twardowski Alfalfa saponins - the allelopathic agents - W Oleszek, M Jurysta and P M Gorski Allelopathy in alfalfa and other forage crops in United States - D A Millar Allelopathy in relation to agricultural productivity in Taiwan: problems and prospects - C-H Chou Effect of pine allelochemicals on selected species in Korea - B-S Kil Allelopathy in Brazil - A G Ferreira, M E A Aquila, U S Jacobi and V Rizvi Allelopathic research activity in Iraq - I S Alsaadawi Impact of allelopathy in the traditional management of agroecosystems in Mexico - A L Anaya, R C Ortega and V N Rodriguez The allelopathic potential of aromatic shrubs in phryganic (East Mediterranean) ecosystems - D Vokou Possible role of allelopathy in growth inhibition of softwood seedlings in Newfoundland - A U Mallik Allelopathy in Quebec forestry - case studies in natural and managed ecosystems - R Jobidon Pigeon pea and velvet bean allelopathy - P Hepperly, H Aguilar-Erazo, R Perez, M Diaz and C Reyes Allelopathy in forest and agroecosystems in the Himalayan region - N P Melkania Neem allelochemicals and insect control - O Koul Allelopathy in management of root-knot nematodes - A Hasan Exploitation of allelochemicals in improving crop productivity - S J H Rizvi and V Rizvi Index.

The effect of nutrients and enriched co2 environments on production of carbon-based allelochemicals in plantago: a test of the carbon/nutrient

Abstract: In a test of the carbon/nutrient (C/N) balance hypothesis, we grew the perennial herb Plantago lanceolata in different CO2 and nutrient environments and then (1) measured the total allocation to shoots, roots, and reproductive parts and (2) quantified aucubin, catalpol, and verbascoside contents of replicate plants of six genotypes. Plants grown under low-nutrient conditions do have higher concentrations of carbon-based allelochemicals than plants grown under high-nutrient conditions. However, in contrast to the C/N balance hypothesis, plants grown in elevated (700 μL·L-1) CO2 conditions had similar, or lower, concentrations of carbon-based allelochemicals than plants grown in ambient (350 μL·L-1 CO2 conditions. We suggest that augmented substrate concentrations (i.e., excess carbohydrates) are a necessary but insufficient trigger for increased secondary metabolism; instead, hormonal and/or direct physical cues (such as light) may be essential to synthesize or activate the appropriate enzyme systems. Moreover, although plant genotype significantly affected plant growth, reproduction, and chemistry, we never observed significant genotype-by-CO2 interactions for these factors, which suggests that changing CO2 environments may not improve the fitness of certain genotypes over others

The Effect of Nutrients and Enriched CO2 Environments on Production of Carbon-Based Allelochemicals in Plantago: A Test of the Carbon/Nutrient Balance Hypothesis

Abstract: In a test of the carbon/nutrient (C/N) balance hypothesis, we grew the perennial herb Plantago lanceolata in different CO2 and nutrient environments and then (1) measured the total allocation to shoots, roots, and reproductive parts and (2) quantified aucubin, catalpol, and verbascoside contents of replicate plants of six genotypes. Plants grown under low-nutrient conditions do have higher concentrations of carbon-based allelochemicals than plants grown under high-nutrient conditions. However, in contrast to the C/N balance hypothesis, plants grown in elevated (700 μL·L-1) CO2 conditions had similar, or lower, concentrations of carbon-based allelochemicals than plants grown in ambient (350 μL·L-1 CO2 conditions. We suggest that augmented substrate concentrations (i.e., excess carbohydrates) are a necessary but insufficient trigger for increased secondary metabolism; instead, hormonal and/or direct physical cues (such as light) may be essential to synthesize or activate the appropriate enzyme systems. More...

Allelopathic effects by Empetrumhermaphroditum on seed germination of two boreal tree species

Abstract: Indoor and outdoor experiments demonstrated that allelopathy is an important factor explaining seed regeneration failures of Scots pine (Pinussilvestris L.) in forest floor vegetation dominated by the dwarf shrub Empetrumhermaphroditum Hagerup. Scanning electron micrograph views of the leaf surfaces of E. hermaphroditum reveal secretory glands that are shown to be involved in the release of water-soluble phytotoxic substances. Bioassays indicate that low doses and short exposure times of seeds to leachates have strong negative effects on germination and early root development. Activated carbon can eliminate the inhibitory effects of leachates and litter. This technique demonstrates the occurrence of allelopathic interference by E. hermaphroditum on seed germination of both Scots pine and aspen (Populustremula L.). In a field experiment the allelopathic effects by E. hermaphroditum are strong during early spring when germination and growth initiate and ground ice still is present. Extracts passed through s...

Comparison of osmotic and allelopathic effects of grass leaf extracts on grass seed germination and radicle elongation

Abstract: The influence of osmotic effects of aqueous plant extracts on the results of allelopathy bioassays was investigated for four pasture grass species. It was found that allelopathic effects were substantially overestimated when osmotic effects were not taken into account. It is concluded that bioassays using aqueous plant extracts are more realistic when osmotically adjusted control values (with the same osmotic potential as the plant extract being tested) are used.

Allelochemicals from Polygonum sachalinense Fr. Schm. (Polygonaceae)

Abstract: The root exudates fromPolygonum sachalinense in a recirculating system significantly inhibited lettuce seedling growth. The rhizomes and roots ofP. sachalinense were extracted with 80% acetone. Bioassay of the neutral-acidic fraction on the TLC agar plate showed the inhibitory activity corresponded to the two yellow pigment bands. Two orange needles were isolated and identified as anthraquinone compounds: emodin and physcion. Both compounds exhibited inhibitory activities against the seedling growth of several testing plant species. Glucosides were isolated fromP. sachalinense and were identified as emodin-1-O-β-D-glucoside and physcion-1-O-β-D-glucoside, respectively. On plant growth bioassay, these glucosides showed no phytotoxic activity against lettuce seedlings. The concentrations of emodin, physcion, and their glucosides from rhizome with roots, aerial parts, fallen leaves, and soil were determined. The rhizome with roots and fallen leaves contained emodin and physcion at relatively high concentrations. Emodin also occurs in the soil of this plant community with effective concentrations in the fall. The results indicate that these anthraquinones are responsible for the observed interference and are potent allelopathic substances.

Exploitation of allelochemicals in improving crop productivity

Abstract: During the recent past, the importance of allelopathy in nature as well as in agroecosystems has attracted worldwide attention. In the beginning, allelopathic studies were limited to the effect of one plant on the other, without much knowledge about the chemicals responsible for such effects. Later, active involvement of scientists belonging to various disciplines, made allelopathy a multidisciplinary subject. Consequently, several allelochemicals which were at the helm of the entire allelopathic affair were isolated, identified and their effects were studied not only on germination, growth or metabolism but also at the molecular level. These developments slowly transformed allelopathic research from basic to applied, and ideas were floated to exploit allelopathy/allelochemicals in various ways in agriculture and forestry (Rice, 1984; Thompson, 1985; Putnam and Tang, 1986; Waller, 1987). We started working with allelochemicals during 1976 and remained concerned mainly with exploring various aspects of allelopathy that may lead to increased crop production. In this chapter we shall discuss some of our work on the potential of allelochemicals in pest control, crop rotation and also discuss the implications of allelopathy in agroforestry, a relatively younger aspect of allelopathic research.

Allelopathic effects of water extracts ofArtemisia princeps var.orientalis on selected plant species.

Abstract: The allelopathic effects of wormwood plants (Artemisia princeps var.orientalis) and their possible phytotoxicity on receptor species were investigated. The aqueous extracts of mature leaf, stem, and root of wormwood plants caused significant inhibition in germination and decreased seedling elongation of receptor plants, whereas germination of some species was not inhibited by extracts of stems and roots. Dry weight growth was slightly increased at lower concentrations of the extract, whereas it was proportionally inhibited at higher concentrations. The calorie value of the organic matter in receptor plants measured by bomb calorimeter was reduced proportionally to the extract concentration. However, results with extracts of juvenile leaf did not correlate with inhibition or promotion of elongation and dry weight.

Allelopathy of yellow fieldcress (Rorippa sylvestris): Identification and characterization of phytotoxic constituents.

Abstract: Both the neutral and acidic fractions of the acetone extract of yellow fieldcress (Kireha-inugarashi,Rorippa sylvestris Besser) inhibited lettuce seed germination. Salicylic,p-hydroxybenzoic, vanillic, and syringic acid were identified in the acidic fraction. In the neutral fraction, hirsutin (8-methylsulfinyloctyl isothiocyanate), 4-methoxyindole-3-acetonitrile, and pyrocatechol were identified. Bioassay using a root exudate recirculating system showedR. sylvestris during flowering inhibited the lettuce seedling growth. Hirsutin (13μg/plant/day) and pyrocatechol (9.3μg/plant/day) were the major compounds released into the rhizosphere. Several combinations of pyrocatechol,p-hydroxybenzoic acid, vanillic acid, and hirsutin reduced lettuce seedling growth. These compounds seemed to be allelochemicals.

A conceptual framework for assessing allelochemicals in the soil environment

Abstract: There has been a surge of interests in recent years on the phenomenon of allelopathy, the chemical agents involved in allelopathy, and the role of allelopathy in crop production (Chou and Waller, 1983; Rice, 1984; Thompson, 1985; Waller, 1987). Studies have generally concentrated either on the symptoms and severity of the adverse effects on affected plants or on the production and identification of the allelochemicals from producing organisms. Few reports have considered the mechanisms and processes involved in the overall relationship from the production of the allelochemicals to the actual occurrence of allelopathy. To be sure, a number of chemicals have been implicated in allelopathic relationships, the phytotoxic nature of these chemicals has been demonstrated, and these chemicals have been isolated from the surroundings of affected plants. Invariably the relationship has been established by inference rather than by direct evidence showing that the isolated chemicals actually caused the allelopathic effects. As Fisher (1979) remarked: ‘It seems unlikely that the allelochemicals that may be extracted from plant material are actually those that reach the host plant, yet all our information on allelopathic compounds is derived from extracts that have never been exposed to the soil.’

Concentration Dependency and Stage of Crop Growth in Alfalfa Autotoxicity

Abstract: Shoots of alfalfa (Medicago sativa L.) contain water-soluble chemical compounds which are autotoxic, i.e., inhibit the growth of alfalfa itself. The objectives of this study were to (i) determine the inhibition threshold of the water-soluble chemical compounds (autotoxic principle), and (ii) demonstrate that the inhibition of seed germination on early seedling growth of alfalfa is due to autotoxinic compounds from alfalfa shoots and not from microbes. A farmer must make a decision on whether or not it would be advisable to replant alfalfa based on the level of alfalfa residue still growing in the field. Laboratory and greenhouse studies were conducted to determine if autotoxicity in alfalfa due to water-soluble compounds is concentration dependent. Filter-sterilized and non-filter-sterilized shoot aqueous extracts from vegetative and reproductive stages of ‘WL-316’ alfalfa were assayed at 20, 40, 60, and 80 g L⁻¹ (fresh shoot weight basis) for their effect on seed germination and root and shoot elongation of seedlings of WL-316 alfalfa in a growth chamber. Compared with the control, root length, shoot length, and germination were inhibited beyond 20 g L⁻¹ concentration. Shoot extract from the reproductive stage was more inhibitory than from the vegetative stage under laboratory conditions. In the greenhouse, incorporation of 4-wk-old green herbage from vegetative stage beyond 48 shoots per square meter level resulted in severe reductions in seedling emergence and plant fresh weight per unit area. Among the several phenolic compounds assayed for their phytotoxicity on root and shoot growth of alfalfa, coumarin and transcinnamic acid at 60 ± 10 μg mL⁻¹ were the most inhibitory. Mixtures of five or more phenolic acids were more phytotoxic than their respective individual components except in the case of trans-cinnamic acid and coumarin. Autotoxicity in alfalfa may be caused by an interaction of many, yet uncharacterized chemical compounds present in shoots.

Allelopathy of Sasa cernua.

Abstract: Sasa (Sasa cernua Makino) is a very serious weed pest. Its allelopathy was studied using lettuce, wheat, timothy, and green amaranth as testing species. Cultured in the rhizosphere soil ofSasa cernua, the seedlings were inhibited by 42-80% compared with the controls cultured in normal soil and vermiculite. The phenolic fraction extracted with 1 M NaOH from the rhizosphere soil ofS. cernua caused significant inhibitions on the seed germination and seedling growth of lettuce, timothy, green amaranth, and barnyard grass.p-Coumaric, ferulic, vanillic, andp-hydroxybenzoic acids andp-hydroxybenzaldehyde were identified as the main allelochemicals in sasa soil by HPLC and [(1)H]NMR. Their contents in the rhizosphere soil were 5640, 1060, 860, 810 and 630 μg/100 g soil. The neutral fraction inhibited the seed germination and seedling growth of lettuce in the TLC direct bioassay. Volatile compounds released from sasa leaves also inhibited the growth of lettuce, wheat, timothy, and green amaranth grown under light, and the growth of etiolated seedlings of barley and wheat. These results confirm thatS. cernua produces typical allelopathy through its rhizosphere soil and air space.

Neem allelochemicals and insect control

Abstract: Most living plants have some degree of resistance to natural enemies due to the presence of secondary plant compounds (allelochemicals). It is well known that plants are used as food sources by many insects and plants, therefore, have evolved many barriers against herbivores (Janzen, 1981) including competitive production of biomass, morphological features (e.g. spines) and secondary plant compounds (the allelochemicals) which act as protective agents against herbivorous insects. While monophagous insects are usually limited to plants whose constitution is apparently not acceptable to other phytophagous species because they contain unpalatable and/or toxic substances, adapted herbivores, have evolved the ability to cope with these plant toxins and avoid deleterious effects.

Do defoliation and subsequent phytochemical responses reduce future herbivory on oak trees

Abstract: Perennial plants are thought to respond to partial or complete defoliation by producing new foliage that is less susceptible to herbivores because of induction of allelochemicals. Here, I tested this hypothesis by manually removing primary foliage from branches ofQuercus emoryi (Fagaceae) at two different times in the season and monitoring changes in protein and tannin levels and the amount of herbivory relative to control branches. New, secondary leaves had 2.5 × greater hydrolyzable tannin content than mature foliage of control branches. Condensed tannins, which constitute a relatively low fraction of leaf mass, were lower, while protein content was temporarily greater, in new secondary leaves relative to mature leaves. Despite large increases in hydrolyzable tannins, herbivory levels were greater on refoliated branches than on control branches. New foliage is susceptible to herbivory regardless of when it is produced in the season, possibly because lower toughness and higher water content override any induced or developmentally related changes in allelochemistry. My results do not support the hypothesis that postherbivore changes in phytochemistry protect perennial plants from future herbivory, at least within a growing season.

Allelopathic effects on nitrogen cycling

Abstract: Molisch (1937) coined the term allelopathy to refer to inhibitory or stimulatory biochemical interactions between plants, including the microorganisms traditionally placed in the plant kingdom. Thus, allelopathy could conceivably affect all phases of the nitrogen cycle which involve plants and microorganisms. This obviously includes most phases of the cycle.

Effect of pine allelochemicals on selected species in Korea

Abstract: The allelopathic potential of red pine (Pinus densiflora), pitch pine (Pinus rigida) and black pine (Pinus thunbergii) has attracted attention of Korean botanists for the last several years. It has been a point of interest why the understorey species are sparse (Lee and Monsi, 1963) and species growing there were similar with the other pine understoreys. It was hypothesized that the similarity of floristic composition of pine stands was caused by some regulating mechanism controlled by pine through the release of certain toxic substances (allelochemicals) in the soil. When the greenhouse soil was mixed with pine leaves, the growth of the plants was suppressed. However, the toxicity of the soil was gradually reduced, and ultimately diminished after several years. This further strengthened the idea of the possible release of allelochemicals by pine. Therefore, it deemed necessary to verify experimentally whether pine is indeed producing allelochemicals which, in turn, affect neighbouring plants. For this, several experiments were performed involving various species growing inside and outside the pine forests. The results obtained from various laboratory and field studies with respect to the allelopathic effects of pine and details of isolation of allelochemicals from pine materials are reported here.

Allelopathy of velvetbean [Mucuna pruriens]: Its discrimination and identification of L-DOPA as a candidate of allelopathic substances

Abstract: A series of the studies conducted through the laboratory bioassays and field tests to search for allelopathic plants indicated that among the 70 plant species tested, velvetbean (Mucuna pruriens var. utilis) was the most promising candidate. It is recognized that velvetbean, which is a tropical legume grown for green manure, has a special ability to smother weeds. The studies placed emphasis on evaluation of allelopathic properties of velvetbean. The field test showed the smallest weed population in the velvetbean stand plots as compared with the stand plots of tomato, eggplant, upland rice and fallow conditions. By means of HPLC and bioassay on germination and seedling growth tests, the substance inhibiting plant growth was identified as L-3,4-dihydroxyphenylalanine (L-DOPA). L-DOPA is a well-known substance biologically active in animal physiology, such as a precursor of neurotransmitter dopamine, and an intermediate of many alkaroids. The present studies revealed that L-DOPA contained in a large amount (about 1% of the fresh weight in leaves and roots of velvetbean) inhibited the growth of some companion plants, and that it probably contributed to its allelopathy. L-DOPA suppressed the growth of some broad leaf weed, while little effect was observed on gramineous plants. In addition to its effectiveness as a green manure, velvetbean could be utilized as an allelopathic crop to control weeds

Assessment of allelopathic potential inArtemisia princeps var.Orientalis residues.

Abstract: Field and laboratory studies were conducted to examine the differential phytotoxicity of residues ofArtemisia princeps var.orientalis (wormwood) using various plants as test species. Seedling elongation and dry weights of receptor plants were inversely proportional to the concentration and incubation time of dry leaves ofA. princeps var.orientalis in vermiculite. In seedling growth tests with abandoned field soils (control) and soil underneath wormwood plants (test), the elongation, dry weight, and caloric content of seedlings grown in the soil from under wormwood plants were severely inhibited, thereby suggesting that certain growth inhibitors were released from wormwood and the inhibitor remained in the soil.

Variation within flax (Linum usitatissimum) and barley (Hordeum vulgare) in response to allelopathic chemicals.

Abstract: A possible method of manipulating allelopathy would be to develop crop varieties showing an increased tolerance to allelopathic chemicals. We therefore examined four flax (Linum usitatissimum) varieties and two wild Linum species in the presence of p-coumaric acid and four barley (Hordeum vulgare) varieties in the presence of p-coumaric acid, scopoletin and wild oat (Avena fatua) extract. Analysis of variance indicates significant interaction between variety and treatment for shoot and root growth for seedling flax, shoot growth for older flax, and root growth for seedling barley. These differences in tolerance between varieties could be exploited to develop-varieties with greater tolerances to the allelochemicals produced by weeds or in crop residues and therefore potentially more tolerant of the presence of weeds.

Allelopathy in forest and agroecosystems in the Himalayan region

Abstract: A great variety of metabolic chemicals potentially involved in plant-plant chemical interactions are released from plants primarily through leaching from aboveground parts, thus, play a significant role in plant interactions on a day-to-day basis (Tukey, 1970). The plant leachates have an effect upon the soil structure, texture, aeration, permeability and exchange. Roots, especially those of large plants, extract substances from deep and distant areas of the soil from where they are translocated into the plant system, later to be returned to the soil by leaching and litter fall. Forest litter has long been recognized as a possible deterrent to tree seedling establishment (Koroleff, 1954), and differences in germination and growth of plant species beneath trees of various species are well known (Telfer 1972). Thus, trees build a characteristic profile of their own by this method; however, the magnitude of materials supplied to the soil layers depends upon the rate of leaching, litter fall and chemical disintegration of the compounds in the environment.

Effect of pine allelochemicals on selected species in Korea

Abstract: The allelopathic potential of red pine (Pinus densifiora) , pitch pine (Pinus rigida) and black pine (Pinus thunbergii) has attracted attention of Korean botanists for the last several years It has been a point of interest why the understorey species are sparse (Lee and Monsi, 1963) and species growing there were similar with the other pine understoreys It was hypothesized that the similarity of floristic composition of pine stands was caused by some regulating mechanism controlled by pine through the release of certain toxic substances (allelochemicals) in the soil When the greenhouse soil was mixed with pine leaves, the growth of the plants was suppressed However, the toxicity of the soil was gradually reduced, and ultimately diminished after several years This further strengthened the idea of the possible release of allelochemicals by pine Therefore, it deemed necessary to verify experimentally whether pine is indeed pro­ ducing allelochemicals which, in turn, affect neighbouring plants For this, several experiments were performed involving various species grow­ ing inside and outside the pine forests The results obtained from various laboratory and field studies with respect to the allelopathic effects of pine and details of isolation of allelochemicals from pine materials are reported here

EFFECTS OF WATER EXTRACTS OF var. orientalis ON SELECTED PLANT SPECIES

Abstract: The allelopathic effects of wormwood plants (Artemisia princeps var. orientalis) and their possible phytotoxicity on receptor species were investigated. The aqueous extracts of mature leaf, stem, and root of worm- wood plants caused significant inhibition in germination and decreased seed- ling elongation of receptor plants, whereas germination of some species was not inhibited by extracts of stems and roots. Dry weight growth was slightly increased at lower concentrations of the extract, whereas it was proportion- ally inhibited at higher concentrations. The calorie value of the organic matter in receptor plants measured by bomb calorimeter was reduced proportionally to the extract concentration. However, results with extracts of juvenile leaf did not correlate with inhibition or promotion of elongation and dry weight.