Importance Of Allelopathy Research Articles

Importance of allelopathy in agriculture: Bioavailability and functions of allelochemicals in soil environment

Weed invasion and subsequent infestation represents a major problem in crop production. Chemical weed control is the major management tactic used in conventional agriculture. Complementary strategies to herbicides are increasingly being investigated. The importance of allelopathy has been considered for weed management over the years. However, the relevance of allelopathy has been highly discussed due to the lack of phytotoxic concentrations of allelochemicals under field conditions. Avena fatua, Brassica nigra, Fagopyrum esculentum, Secale cereale, Sorghum bicolor, Triticum aestivum and other cover crops have been used in weed management on a limited basis. Crop residues from existing crop or rotational crops can provide selective weed suppression through their physical presence on the soil surface and/or through the release of allelochemicals. Some of the allelochemicals have been reported to play a role in weed management, including phenolic acids, DIBOA, DIBOA-glycoside, and BOA, dhurrin, fatty acids, hydroxamic acids, isoflavonoids, isothiocyanate, juglone, momilactone, scopoletin, and sorgoleone. The soil system, a living and dynamic, influences the fate and functions of allelochemicals in time and space. The bioavailability of allelochemicals in the soil is dependent on processes such as adsorption, leaching and degradations by abiotic and biotic factors. The clay types, organic matter, and soil pH can affect the bioavailability of allelochemicals in the soil. Thus, the allelopathic potential of many compounds may not be expressed in some soils because of the chemical adsorption to soil colloids. The resulting concentrations (sub-toxic) of any of these allelochemicals in soil matrix may have a variety of functions that influence seed germination, seedling emergence, plant growth suppression, nutrient acquisition or soil microbial activity. Examples of such compounds are benzoic acid, catechin, coumaric acid, dihydroxyphenylalanine, ferulic acid, hydroxybenzoic acid, sorgoleone, vanillic acid, and others.

Allelopathic interactions involving benthic phototrophic microorganisms.

As a way to prevent resource depletion by other species, many phototrophic aquatic microorganisms produce inhibitory compounds. This process, known as allelopathy, has been widely studied in planktonic environments, where it is recognized as being a driving force of planktonic communities. However, in benthic environments, biofilms provide very particular micro-environments. The present review focuses on allelopathic interactions involving benthic phototrophic prokaryotes and micro-eukaryotes ('microalgae'), which generally form biofilms, and includes any interaction involving benthic microalgae either as the emitter or as the target in both marine and freshwater habitats. To support our hypothesis on the importance of allelopathy in biofilms due to the particularities of biofilms, we show that (i) reported allelopathic species and compounds are diverse and numerous in the three major groups of benthic phototrophic microorganisms, (ii) allelopathic benthic species could affect community composition, (iii) allelopathy in biofilms is currently underestimated because of the lack of suitable methods. As benthic primary producers represent an important source of organic carbon in some streams and littoral areas, these interactions could impact the whole ecosystem in these areas, probably more than in areas dominated by planktonic communities.

Plants Release Precursors of Histone Deacetylase Inhibitors to Suppress Growth of Competitors.

To secure their access to water, light, and nutrients, many plant species have developed allelopathic strategies to suppress competitors. To this end, they release into the rhizosphere phytotoxic substances that inhibit the germination and growth of neighbors. Despite the importance of allelopathy in shaping natural plant communities and for agricultural production, the underlying molecular mechanisms are largely unknown. Here, we report that allelochemicals derived from the common class of cyclic hydroxamic acid root exudates directly affect the chromatin-modifying machinery in Arabidopsis thaliana. These allelochemicals inhibit histone deacetylases both in vitro and in vivo and exert their activity through locus-specific alterations of histone acetylation and associated gene expression. Our multilevel analysis collectively shows how plant-plant interactions interfere with a fundamental cellular process, histone acetylation, by targeting an evolutionarily highly conserved class of enzymes.

Alelopatia de duas espécies de braquiária em sementes de três espécies de estilosantes

A alelopatia é muito comum em gramíneas como a Brachiaria brizantha e B. decumbens, podendo representar um problema em pastagens consorciadas com Stylosanthes, já que, nessa situação, a perpetuação da leguminosa depende da ressemeadura natural. Apesar da grande quantidade de sementes de estilosantes produzidas anualmente, nessas pastagens consorciadas, observa-se, em campo, pequena quantidade de plantas jovens, o que pode ser atribuído a um possível efeito alelopático da gramínea. Considerando a importância da alelopatia no consórcio de braquiárias com estilosantes, testou-se o potencial alelopático de extratos de Brachiaria brizantha e B. decumbens na germinação de sementes de três espécies de estilosantes. Verificou-se que há efeito alelopático negativo de B. brizantha e B. decumbens na germinação de sementes de Stylosanthes guianensis e somente de B. decumbens na germinação de S. capitata; há efeito alelopático positivo de B. brizantha nas sementes de S. macrocephala; não há efeito alelopático de B. brizantha na germinação de sementes de S. capitata e nem de B. decumbens em S. macrocephala.

Comparisons of Phytotoxicity of Barley Parts Extracts in Three Growth Stages on Annual Ryegrass

Problem statement: The importance of allelopathy in nature and in agroecosystem has attracted researcher's attention with the main goal of using the phenomenon in biological control of weeds. currently, active involvement of scientists from different disciplines made allelopathy a multidisciplinary subject, and transformed the research from basic to applied, enabling use of allelopathy in agriculture and forestry. Screening accessions of allelopathic crops and natural vegetation for their ability to reduce weeds is the basic approach for utilizing the phenomenon. Approach: Phytotoxicity of barley extracts (Hordeum vulgare L.) on Annual ryegrass (Lolium rigidum L.) was investigated. Water extracts of barley, four varieties were bioassayed on germination and seedling growth of Lolium rigidum to: (i) test the heterotoxicity of barley on Lolium rigidum, (ii) study the dynamics of allelopathic potential over three growth stages and (iii) identify the most allelopathic plant part of barley. Roots, stems and leaves were extracted at three growth stage separately. (iv) indicated which variety has the highest allelopathic potential. Results: Seedling growth bioassays demonstrated that the Lolium rigidum responded differently to the allelopathic potential of barley. For Lolium rigidum radicle growth and germination were more depressed than coleoptile growth, though. The allelopathic potential of barley plant parts was not stable over its life cycle for Lolium rigidum. Leaves were the most phytotoxic barley plant parts for Lolium rigidum in the all stages. Leaves extract of barely at stage 11 had the highest inhibition on germination. The most inhibition of coleoptile growth when treated with leaves extract at stage 11.At stage 8 the leaves extract of Jonob variety had the highest inhibition on radicle growth of Lolium rigidum. Conclusions: Results suggested that the response by Lolium rigidum varied depending on the source of allelochemicals (plant part) and the growth stage of the barley plant and kind of variety.

Fate of allelochemicals in the soil

Allelochemicals are compounds released by one plant or plant residues that may have a negative or positive effect on other plant. The importance of allelopathy was extensively explored during the past three decades, with the work concentrating in the extraction and identification of the chemicals, and demonstration of activity in petry dish experiments. These compounds interact in the soil environment similarly as herbicides and are subject to processes of degradation such as microbial degradation, oxidation, and photolysis, and processes of removal or transfer, such as volatilization and adsorption. The objective of this review was to access the fate of allelochemicals in the soil environment to help to find strategies to increase its activity. The activity of allelochemical is limited in time (because of slow release from the donor material) and in space (because of the interaction with the environment). Demonstration of allelopathy should include the fate of the proposed chemical in the soil environment, presenting studies of degradation and removal processes.