Showing papers on "Allelopathy published in 2002"

Cost of defense in the context of plant competition: brassica rapa may grow and defend

Abstract: Theory on costs of plant defense against herbivory in stressful environments predicts that costs should increase when competition is intense. This amplifies a fundamental dilemma that plants are thought to face: allocate limited resources to grow fast enough to compete, or invest these resources in secondary metabolites to maintain defense. We studied costs associated with genetic and environmental variation in secondary metabolite pro- duction of Brassica rapa in the presence and absence of the generalist competitor Lolium perenne. We used experimental quantitative genetics (artificial selection) to manipulate genetic variation, and herbivore-induction treatments to produce environmental variation in myrosinase and glucosinolate concentrations and resistance. Glucosinolates, and their byproducts after breakdown by myrosinase, are known to affect herbivory on plants in the Brassicaceae family. Defense costs were significant in the absence of competitors, but in contrast to theoretical predictions, costs of constitutive defense (measured as growth rates) were not detectable and the cost of induced defense remained the same in the competitive environment. To understand what factors made constitutive defense costs not detectable under competition we conducted several experiments to assess the effects of limited re- sources and allelopathy on costs and benefits of the defense chemicals. None of the ex- periments involving nutrient supply and weak competition supported the hypothesis that the lack of defense costs in competitive environments was due to limited resources. Instead, the breakdown products of the glucosinolate-myrosinase reaction appeared to function as allelopathic agents, which may benefit B. rapa plants in competition, thereby reducing net costs of chemical defense. We found that: (1) the effects of exogenous glucosinolates on Lolium root length depended on the presence of myrosinase. (2) In the absence of nutrients, Lolium root lengths were shorter when seeds germinated with B. rapa. (3) Genetic increases in glucosinolate concentration negatively affected Lolium seedling growth only when there were simultaneous genetic increases in myrosinase concentration. Activated carbon treat- ments designed to neutralize allelopathic effects and restore costs in the competitive en- vironments were, however, not statistically significant. When plant defenses also function to benefit plants in competitive interactions, plants may evolve to compete and defend.

Improving crop competitive ability using allelopathy — an example from rice

Abstract: The objective of this paper is to review the possibilities for using allelopathy to improve overall crop competitive ability against weeds, using rice, Oryza sativa, as an example Laboratory, greenhouse and field screenings for allelopathy and overall weed suppression in rice have been made and allelopathic rice germplasm has been identified in laboratory and greenhouse screening Field experiments revealed that allelopathy accounted for 34% of overall competitive ability in rice For strongly allelopathic cultivars, allelopathy was the dominant factor determining competitive ability Based on the results of the screenings, recombinant inbred line populations were developed for identification of quantitative trait loci (QTL) controlling allelopathy Populations of recombinant inbred lines (RILs) were derived through single-seed descent from crosses between varieties with contrasting behaviour and QTL controlling allelopathy were identified For rice and most probably also for other cereal crops, the findings presented can explain the limited success in previous breeding programmes for weed competition, as allelopathy has never before been acknowledged as an important factor The findings in allelopathy indicate that it is possible to improve allelopathy in rice using marker-assisted selection Optimizing allelopathy in combination with breeding for competitive plant types could result in crop cultivars with superior weed-suppressive ability

Control of witchweed Striga hermonthica by intercropping with Desmodium spp., and the mechanism defined as allelopathic.

Abstract: During investigations into the control of insect damage to maize crops in subsistence farming in Kenya, which involved intercropping with repellent plants, the fodder legumes silverleaf (Desmodium uncinatum) and greenleaf (D. intortum) were also found to reduce dramatically the infestation of maize by parasitic witchweeds such as Striga hermonthica. This effect was confirmed by further field testing and shown to be significantly greater than that observed with other legumes, e.g., cowpea, as were the concomitant yield increases. The mechanism was investigated, and although soil shading and addition of nitrogen fertilizer showed some benefits against S. hermonthica infestation, a putative allelopathic mechanism for D. uncinatum was observed. In screenhouse studies, a highly significant reduction in S. hermonthica infestation was obtained when an aqueous solution, eluting from pots in which D. uncinatum plants were growing, was used to irrigate pots of maize planted in soil seeded with high levels of S. hermonthica. Growth of the parasitic weed was almost completely suppressed, whereas extensive infestation occurred with the control eluate. Laboratory investigations into the allelopathic effect of D. uncinatum, using samples of water-soluble chemical components exuded from cleaned roots, demonstrated that this involved a germination stimulant for S. hermonthica and also an inhibitor for haustorial development.

Allelopathic Effects of Parthenium hysterophorus Extracts on Seed Germination and Seedling Growth of Eragrostis tef

Abstract: The present study was conducted to investigate the allelopathic effects of Parthenium hysterophorus weed on seed germination and seedling growth of tef. Flower, stem, root and leaf aqueous extracts of Parthenium at 0, 1, 5, and 10 % concentrations were applied to determine their effect on tef seed germination and seedling growth under laboratory conditions. Increasing concentrations of aqueous extracts of Parthenium from leaf and flower inhibited seed germination and complete failure of seed germination was recorded when the extract concentration from the leaf part was 10 %. In contrast, aqueous extracts from stem and root had no effect on tef seed germination. Roots appeared more sensitive to allelopathic effect than shoots. Extracts from flower, root and stem had a stimulatory effect on shoot length at all concentration levels, as against an inhibitory effect of leaf extracts. Root extracts at low concentration (1 %) greatly promoted root length but aqueous extracts from leaf and flower inhibited root length.

Allelopathic potential and chemical constituents of volatiles from Ageratum conyzoides under stress.

Abstract: The allelopathic potential of Ageratum conyzoides was investigated under different environmental stress conditions, including nutrient deficiency, physical damage, 2,4-D treatment, competition with Bidens pilosa, infection with Erysiphe cichoracearum, and feeding by Aphiids gossypii. The inhibitory effects of A. conyzoides volatiles on peanut (Arachis hypogaea), redroot amaranth (Amaranthus retroflexus), cucumber (Cucumis sativus), and ryegrass (Lolium multiforum) increased when plants were grown under nutrient-deficient conditions or in competition with B. pilosa; however, there was no difference with physical damage or 2,4-D treatment. Phytoinhibitory effects decreased under fungal infection and aphid feeding. Volatiles from A. conyzoides plants infected with E. cichoracearum or exposed to A. gossypii feeding inhibited or killed fungi and insects. Precocenes and their derivatives, monoterpenes, and sesquiterpenes were the major volatile components of A. conyzoides.

Why phenolic acids are unlikely primary allelochemicals in rice.

Abstract: Allelopathy in rice (Oryza sativa, L.) effective against weeds has been found in about 3.5% of tested rice germplasm in both laboratory and field experimentation. However, the allelochemicals responsible for growth inhibition of rice-associated weeds have not yet been identified. In the literature, phenolic acids are often mentioned as putative allelochemicals. If phenolic acids commonly reach growth inhibitory concentrations in rice ecosystems, it must be expected that the degree of tolerance to phenolic acids will vary among traditional rice cultivars or plant species adapted to rice environments having inherently different phenolic acid concentrations. Phenolic acids concentrations are normally greater in submerged than in aerobic soils. A dose–response study, however, showed that seedlings of rice cultivars adapted to submerged anaerobic soils did not have higher level of tolerance against p-hydroxybenzoic acid than did seedlings of varieties adapted to aerobic upland soils. Moreover, traditional rice cultivars had no greater tolerance than did improved cultivars that were recently bred for traits other than tolerance of phenolic acids. Similarly, there were no differences in tolerance of p-hydroxybenzoic acid between two Echinochloa weed species adapted to either anaerobic or aerobic growth conditions. Thus, neither the rice cultivars nor weed species had evolved different tolerance levels against the phenolic acid. However, all rice cultivars had significantly greater tolerance of p-hydroxybenzoic acid than did either weed species. In a second experiment, the rates at which rice plants released phenolic acids into solution cultures were measured for at least one month, the time period of greatest allelopathic activity following planting under field conditions. The maximum release rate of phenolic acids during the first month of growth was approximately 10 μg/plant/day. At a conventional plant density, the release rate of phenolic acids would be approximately 1 mg/m2day. This order of release rate cannot provide concentrations remotely close to phytotoxic levels determined for these rice cultivars and weed species. The results presented in this paper do not preclude the possibility that phenolic acids might be one component in a mixture of chemicals that, when present simultaneously, are allelopathic.

Allelopathy : from molecules to ecosystems

Abstract: The physiology of allelochemical action, clues and views, F.A. Einhellig physiological basis for allelochemical action of ferulic acid, M.N.V. Prasad and S. Rama Devi photosynthetic functions of leaves affected by the bibenzyl batatasin-III, A. Wallstedt et al allelopathic concentrations of coumarins and other phenolics under stress conditions and their histological localization, A.M. Zobel et al the role of caffeine in the production decline due to autotoxicity in coffee and tea plantations, Ana L. Anaya et al fescue ecology, physiology and allelopathy - a case study, C. Bertin and L.A. Weston ecophysiological roles of selected lichen secondary compounds, J.G. Romagni et al phenolic compounds from olive oil mill wastewater against the "tricky germination" of two worst weeds, G. Aliotta et al strategies for research in applied aspects of allelopathy, S.O. Duke et al plants as sources of natural herbicides against branched broomrape, J.R. Qasem allelochemicals as herbicides, S.O. Duke et al towards utilization of allelopathy - the rice example, M. Olofsdotter et al crop allelopathy for weed management in sustainable agriculture, S.S. Narwal stress and allelopathy, M.J. Reigosa et al allelopathic interaction in forest ecosystems, F. Pellisier et al multifacet approach to study allelochemicals in an ecosystem, Inderjit secondary metabolites as allelochemicals in plant defence against microorganisms of the phyllosphere, K. Karamanoli on the question of paradigm in the science of allelopathy, A.U. Mallik trends in allelopathy research over six-year period analysis (1995-2000), Emilio V. Carral Vilarino cluster analysis, a valuable tool for allelopathic SAR studies?, F.A. Macias et al.

Chemical ecology of plants : allelopathy in aquatic and terrestrial ecosystems

Abstract: Problems and prospects in the study of plant allelochemicals: a brief introduction.- Antifungal properties of cyanobacteria and algae: ecological and agricultural implications.- The chemistry and chemical ecology of biologically active cyanobacterial metabolites.- Compounds from Typha domingensis P..- Allelochemicals from sunflowers: chemistry, bioactivity and applications.- Feedback mechanism in the chemical ecology of plants: role of soil microorganisms.- Do allelochemicals operate independent of substratum factors?.- Ecological relevance of allelopathy: some considerations related to Mediterranean, subtropical, temperate, and boreal forest shrubs.- Linking ecosystem disturbance with changes in keystone species, humus properties and soil chemical ecology: implications for conifer regeneration with ericaceous understory.- Black walnut allelopathy: current state of the science.- Allelopathy and agroecology.- Allelochemicals phytotoxicity in explaining weed invasiveness and their function as herbicide analogues.- Shift in allelochemical functioning with selected abiotic stress factors.- Pitfalls in interpretation of allelochemical data in ecological studies: implications for plant-herbivore and allelopathic research.- Biochemical and physiological aspects of pollen allelopathy.

Biochemical basis for wheat seedling allelopathy on the suppression of annual ryegrass (Lolium rigidum).

Abstract: The chemical basis for wheat seedling allelopathy on the growth of annual ryegrass was investigated by the identification and quantification of multiple allelochemicals from wheat seedlings. Results indicated that 58 wheat accessions differed significantly in seedling allelopathy and inhibited the root growth of ryegrass from 10 to 91%, depending on accession. Analysis of allelochemicals by GC/MS/MS indicated that allelopathy was significantly correlated with the levels of measured allelochemicals in the shoots and roots of young wheat seedlings. Ryegrass root growth was also negatively correlated with the levels of p-hydroxybenzoic, vanillic, and trans-ferulic acids in root exudates. Wheat allelopathic potential was negatively correlated with the levels of the eight known allelochemicals quantified in the shoots, roots, and water−agar medium, with multiple regression coefficients (r) of −0.61, −0.71, and −0.71, respectively. In comparison with weakly allelopathic accessions, strongly allelopathic accessi...

Allelopathy of buckwheat: Assessment of allelopathic potential of extract of aerial parts of buckwheat and identification of fagomine and other related alkaloids as allelochemicals

Abstract: The allelopathic potential of buckwheat (Fagopyrum esculentum) was investigated. Field study showed that living buckwheat reduced weed biomass compared with plots without buckwheat. Laboratory study revealed that root exudates suppressed root and shoot growth of weeds and reduced weed dry weight. Sequential partitioning of the aqueous ethanolic extract of the aerial parts of buckwheat showed that the chloroform extract caused an 80% reduction in radicle elongation of lettuce seedlings at a concentration of less than 100 p.p.m. Fagomine, 4-piperidone and 2-piperidinemethanol were isolated and identified by 1H and 13C nuclear magnetic resonance from the chloroform extract. These compounds caused a 50% inhibition of radicle elongation in lettuce seedlings at concentrations of less than 100 p.p.m. These results suggest that compounds 1, 2, and 3 might act as allelochemicals and affect the growth or germination of different plant species.

Nematicidal and allelopathic potential of Argemone mexicana, a tropical weed.

Abstract: Argemone mexicana L. (Papaveraceae), a tropical annual weed, is phytotoxic to many crop species. This study was designed to examine the allelochemical and nematicidal potential of A. mexicana and to better understand the role of this weed in the ecosystem. A methanol-soluble extract of the leaf material caused greater juvenile mortality of Meloidogyne javanica than did ethyl acetate or hexane extracts indicating the polar nature of the toxins. Decomposing tissues of A. mexicana in soil at 50 g kg−1 were highly deleterious causing 80% mortality of tomato plants. At 10 g kg−1 plant growth was enhanced, while at 30 g kg−1 plant growth was substantially retarded. M. javanica population densities in the rhizosphere and in roots, and gall formation were significantly suppressed when 10, 30 or 50 g kg−1A. mexicana was allowed to decompose in the soil. To establish whether decomposition was necessary to produce phytotoxic symptoms, or whether the shoot extract alone could interfere with plant growth, an aqueous shoot extract was applied to soil. Whereas a 50% extract promoted plant growth, a 100% (100 g/500 mL distilled water) concentration significantly reduced plant height, and fresh weights of shoot and root. In general, decomposing plant material caused greater phytotoxicity compared to the aqueous extract. Addition of N as NH4NO3 partially alleviated the phytotoxic action of A. mexicana,and also reduced severity of root-knot disease. Adding Pseudomonas aeruginosa to soil amended with A. mexicana resulted in decreased density of M. javanicain the rhizosphere and in tomato roots, suppressed galling rates and enhanced plant growth.

Evidence of Tissue-specific Allelopathic Activity in Euthamia graminifolia and Solidago canadensis (Asteraceae)

Abstract: Euthamia graminifolia and Solidago canadensis may be found growing in dense, essentially monospecific, stands. One hypothesis to explain this phenomenon is that both of these goldenrods, as do many related taxa in Asteraceae, release allelochemicals into the surrounding environment. To test this hypothesis, leaf and root/rhizome tissues of both species were screened for allelopathic activity. Aqueous extracts (50 g dried tissue in 2000 ml distilled water) were prepared for each tissue type for each species and a series of dilutions ranging from 0% to 100% of each extract was used for testing radish and lettuce seed germination and root growth. Leaf extracts from both species significantly inhibited seed germination and root growth. Root/rhizome extracts significantly inhibited root growth, but had no effect on seed germination. These results suggest that allelopathy may inhibit the growth and survival of competing species. In addition, both taxa may have a negative effect on yields of nearby crop...

Varietal Differences in Allelopathic Potential of Alfalfa

Abstract: Alfalfa (Medicago sativa L.) plants were found to contain water-soluble substances that inhibited the germination and seedling growth of alfalfa (Chung and Miller 1990, Agron. J. 87, 762—767). Tsuzuki et al. (1999, Rep. Kyushu Branch Crop Sci. Soc. Japan 65, 39—40) discovered allelochemicals in alfalfa plants that could have adverse effects on the growth of some lowland weeds. This study was conducted to investigate varietal differences in allelopathic potential in alfalfa plants. Eight common varieties of Japanese alfalfa (Medicago sativa L.), namely Batasu, Hisawakaba, Kitawakaba, Makiwakaba, Natsuwakaba, Lucerne, Tachiwakaba and Yuba, were grown by conventional methods in the Experimental Field of the Crop Science Laboratory, Faculty of Agriculture, Miyazaki University. Aqueous extracts of both fresh and dried material of alfalfa plants of all varieties significantly inhibited both germination and growth of lettuce (Lactuca sativa L.). Leachates from germinating seeds of almost all alfalfa varieties inhibited elongation of the radicle but produced a negligible increase in germination and only slightly inhibited elongation of the hypocotyl of lettuce plants. Results demonstrated that the degree of inhibition of germination and growth of lettuce varied with the variety of alfalfa. In particular, Lucerne was identified as having the strongest allelopathic potential of the varieties studied. The results suggested that the allelopathic potential of alfalfa might be relating to a gene. Varietatsunterschiede im allelopathischen Potential von Luzerne Luzerne (Medicago sativa L.)-Pflanzen weisen wasserlosliche Substanzen auf, die die Keimung und das Samlingswachstum von Luzerne inhibieren. Es kann angenommen werden, das Luzernepflanzen allelopathisch wirkende Verbindungen aufweisen, die das Wachstum von Unkrautpflanzen des Tieflands beeintrachtigen. Die Untersuchung wurde durchgefuhrt, um das Potential allelopathischer Sortenunterschiede bei Luzerne zu bestimmen. Acht im Anbau verwendete Luzernesorten – Batasu, Hisawakaba, Kitawakaba, Makiwakaba, Natsuwakaba, Lucerne, Tachiwakaba und Yuba – wurden nach konventionellen Verfahren auf dem Versuchsfeld des Pflanzenbauinstitutes der Fakultat der Miyazaki-Universitat angebaut. Wasserige Extrakte von frischen und trockenen Luzernepflanzen hemmten bei allen Sorten signifikant die Keimung und das Wachstum von Salat (Lactuca sativa L.). Auszuge keimender Samen der meisten Luzernesorten inhibierten das Langenwachstum der Wurzel, hatten aber kaum Einflus auf eine Forderung der Keimung und zeigten eine geringe Inhibierung des Langenwachstum des Hypokotyls von Salat. Die Ergebnisse zeigen, das der Grad der Inhibierung der Keimung des Wachstums von Salat abhangig von den gepruften Luzernesorten ist. Lucerne hat das starkste allelopathische Potential der Sorten. Die Ergebnisse lassen vermuten, das das allelopathische Potential genetisch bedingt ist.

Using specific secondary metabolites as markers to evaluate allelopathic potentials of rice varieties and individual plants

Abstract: It is a key of the breeding of allelopathic rice cultivars to evaluate and screen few accessions with allelopathic traits from numerous rice accessions and individual plants. Rice varieties and individual plants with allelopathic traits demonstrated their allelopathic effects by producing and releasing specific secondary metabolites into environment. Therefore, using specific secondary metabolites as markers, the allelopathic potentials of rice varieties and individual plants could be evaluated by HPLC. The allelopathic potentials of 3000 rice accessions and some individual plants of F3 and F4 were evaluated by this method in 1 a. If these accessions and plants were evaluated by the traditional method in the field, it would take more than 10 a, furthermore, the breeding process of allelopathic rice cultivars would be directed and monitored by this method. Isolation and structural identification of specific secondary metabolites was done by LC/MS coupling 1H and 13C NMR. It revealed that allelochemicals of rice tissue were glucosides of resorcinol, flavone and hydroxamic acid, and were not well-known phenolic and fatty acids in previous studies. However, these glucosides could degrade immediately into sugar, phenolic and fatty acids under microbial and acidic medium when they released into the environment.

Black walnut allelopathy: current state of the science

Abstract: Allelopathy, generally defined as any direct or indirect effect by one plant species on another through the production of chemical compounds that are released to the environment [1, 2, 3], has important widespread implications in natural communities and in artificial plant assemblages such as agriculture, horticulture, and forestry [2, 4, 5, 6, 7, 8]. Allelopathic influences may be subtle in natural communities, but they can be more pronounced in artificial communities among plant species whose evolutionary history is seldom connected. Black walnut (Juglans nigra), a tree species often cited as an example of allelopathy, is one of the most valuable hardwood timber species in the United States. It is often found in natural forests and grown in plantations. Anecdotal stories abound of the allelopathic effects of black walnut on associated vegetation, dating back to the first century A.D. [9]. Our knowledge base of black walnut allelopathy has increased steadily over the last two decades, allowing us to distinguish between myths and science. This chapter examines the different facets of black walnut allelopathy in the light of recent advances in chemical ecology.

Screening for effects of phytochemical variability on cytoplasmic protein synthesis pattern of crop plants.

Abstract: Crop plants have to cope with phytochemical variability along with other environmental stresses. Allelochemicals affect several cellular processes. We tested the effect of toxic aqueous leachates from Sicyos deppei, Acacia sedillense, Sebastiania adenophora, and Lantana camara on the radicle growth and cytoplasmic protein synthesis patterns of Zea mays (maize), Phaseolus vulgaris (bean), Cucurbita pepo (squash), and Lycopersicon esculentum (tomato). 2D-PAGE and gel scan densitometry analysis were used to detect differences in cytoplasmic root protein pattern expression. High-, medium-, and low-molecular-weight cytoplasmic proteins were affected by the different aqueous leachates. Crop plant responses were diverse, but in general, an increase in protein synthesis was observed in the treated roots. Maize was the least affected, but both the radicle growth and also the protein pattern of tomato were severely inhibited by all allelopathic plants. The changes observed in protein expression may indicate a biochemical alteration at the cellular level of the tested crop plants.

Isolation and identification of plant growth inhibitors as candidate(s) for allelopathic substance(s), from aqueous leachate from mesquite (Prosopis juliflora (Sw.) DC.) leaves

Abstract: As candidate(s) for allelopathic substance(s), two plant growthinhibitors were isolated from aqueous leachate of leaves of mesquite, whichshowa strong allelopathy, and which were identified as syringin and(–)-lariciresinol by their spectral analyses. Syringin inhibited root andshoot growth of lettuce seedlings at concentrations greater than 0.8μM, and root and shoot growth of barnyard grass seedlings atconcentrations greater than 2.7 and 26.9 μM, respectively. Onthe other hand, (–)-lariciresinol inhibited root and shoot growth oflettuce seedlings at concentrations greater than 2.8 and 0.8μM,and root and shoot growth of barnyard grass seedling at concentrations greaterthan 0.8 and 2.8 μM, respectively. The contents of syringin and(–)-lariciresinol in the rhizosphere soil of mesquite were 0.34 and 0.38μg/g soil, respectively. These results indicate that syringinand (–)-lariciresinol are allelopathic substance(s), and may play rolesinthe allelopathy of mesquite.

Autotoxicity of barley

Abstract: Allelopathic potential of a crop species varies depending on stage of growth. Because allelopathy of barley (Hordeum vulgare L.), an important cereal grain adapted to semi-arid conditions of northern Tunisia, has not been widely reported, a study was conducted to determine i) the potential autotoxicity of barley and ii) the differential allelopathic potential of barley plant components over four phenological stages. The study involved experiments with barley seed germination and seedling growth bioassay techniques for detection of allelopathic activity. Plant parts of field-grown ‘Rihane’ barley were extracted with distilled water. At growth stage 4 (stems not well developed), whole plants were extracted. Thereafter, roots, stems, and leaves were extracted separately. Water extracts of ‘Rihane’ barley plant parts were bioassayed on four varieties of barley. Seedling growth bioassays revealed autotoxicity of barley, which appeared to be more pronounced on radicle growth than coleoptile growth, esp...