Exploiting the allelopathic properties of agricultural crops in low-input cropping systems

The FATEALLCHEM project (5th framework programme) applied a holistic approach and used modern techniques in allelopathy research, concluded on the possibilities of exploiting allelopathic properties of wheat and rye and established a framework for future allelopathy research. An extract of the results of the FATEALLCHEM project will be presented, based on 18 recent papers, published in the Journal of Agricultural and Food Chemistry, 2006, vol 54 (available on the web of JAFC

The ecosystem and evolutionary contexts of allelopathy

Plants can release chemicals into the environment that suppress the growth and establishment of other plants in their vicinity, a process known as ‘allelopathy’. However, chemicals with allelopathic functions have other ecological roles, such as plant defense, nutrient chelation, and regulation of soil biota in ways that affect decomposition and soil fertility. These ecosystem-scale roles of allelopathic chemicals can augment, attenuate or modify their community-scale functions. In this review we explore allelopathy in the context of ecosystem properties, and through its role in exotic invasions consider how evolution might affect the intensity and importance of allelopathic interactions

Allelopathy and Agricultural Sustainability: Implication in weed management and crop protection—an overview

Crop plants have defined roles in agricultural production and feeding the world. They are affected by several environmental and biological stresses, which range from soil salinity, drought, and climate change to exposure to diverse plant pathogens. These stresses pose risk to agricultural sustainability. To avoid the increasing biotic and abiotic pressure on crop plants, agrochemicals are extensively used in agriculture for attaining desirable yield and production of crops. However, the use of agrochemicals is also challenging the integrity of ecosystems. Thus, to maintain the integrity of ecosystem, sustainable measures for elevated crop production are required. Allelopathy, a process of chemical interactions between plants and other organisms, could be used in the management of several biotic and abiotic stresses if the basic mechanisms of the phenomena and plants with allelopathic potentials are known. Allelopathy has a promising future for its application in agriculture for natural weed management, improving soil health and suppressing plant diseases. The aim of this review is to discuss the importance of allelopathy in agriculture and its role in sustainability with a specific focus on weed management and crop protection

Toxin-allelopathy among phytoplankton species prevents competitive exclusion

Toxic or allelopathic compounds liberated by toxin-producing phytoplankton (TPP) acts as a strong mediator in plankton dynamics. On an analysis of a set of phytoplankton biomass-data that have been collected by our group in the North-West part of the Bay of Bengal, and by analysis of a three-component mathematical model under a constant as well as a stochastic environment, we explore the role of toxin-allelopathy in determining the dynamic behaviour of the competing-phytoplankton species. The overall results, based on analytical and numerical wings, demonstrate that toxin-allelopathy due to the toxin-producing phytoplankton (TPP) promotes a stable coexistence of those competitive phytoplankton that would otherwise exhibit competitive exclusion of the weak species. Our study suggests that TPP might be a potential candidate for maintaining the coexistence and diversity of competing phytoplankton species.Comment: 29 pages, 6 figures, Journal Pape

Sources and modes of action of invasive knotweed allelopathy : the effects of leaf litter and trained soil on the germination and growth of native plants

Invasive knotweeds, native to Eastern Asia, are among the most dominant plant invaders of European and North American temperate ecosystems. Recent studies indicate that one cause of this dominance might be allelopathy, but the possible sources and modes of action of this allelopathy are insufficiently understood. Here, we asked whether the invasive knotweed Fallopia × bohemica can exert allelopathic effects on native plants also through its leaf litter, or through persistent soil contaminants, and whether these affect the germination or growth of native plants. In a germination experiment with nine native species neither litter leachate, an aqueous extract of knotweed leaves added to the soil, nor trained soil with a history of Fallopia pre-cultivation suppressed the germination or early growth of natives. A mesocosm study with experimental native communities showed that the presence of F. × bohemica, although not a dominant in these communities, caused significant shifts of life-history strategy in two dominant natives, and that similar effects could be elicited through litter leachates or trained soil alone. However, there were hardly any effects on the biomass of natives. Our study indicates that knotweed allelopathy acts on the growth rather than germination of natives, and that soil contamination through persistent allelochemicals may not be a significant problem in habitat restoration. It also shows that allelopathic effects can sometimes be subtle changes in life-history and allocation patterns of the affected species

Pengaruh Zat Alelopati dari Alang-Alang terhadap Pertumbuhan Semai Tiga Spesies Akasia

Allelopathy is the compound released by the plants (example: blady grass) to the environtment and where another plants is living and could obstruct or extinguish to another plants. The purpose of research were to figure out the effect of allelopathy from the blady grass toward the species of acacia seedlings, to figure out the weakest affected seedling species by blady grass allelopathy, and to figure out interaction between concentration of extracted blady grass and seedling tree species. The research was designed based on factorial in a complete random design. Factor I was the seedlings, consisted of acacia, mangium, and acacia alba, while factor II was concentration of extracted blady grass allelopathy, consisted of non extracted allelopathy, extracted allelopathy 25%, extracted allelopathy 50%, extracted allelopathy 75%, and extracted allelopathy 100%. Every treatment was repeated 5 times. The number of the seedlings for each experimental unit was two seeding. The observed variables were height, diameter of the stem, number of leaves, and living percentage of the seedlings. This observation data was tested by Bartlett test to find the variance homogenity. Then it was analyzed by using variance analysis, and tested by least significant difference (LSD). The calculation were done at 5% significant level. The result of this research showed that allelopathy of blady grass were significan to the growth of acacia, mangium and acacia alba seedlings. Based on the LSD at 5% was known that the concentrate of blady grass allelopathy had strongest negative effect to the growth seedlings was 100%. Seedling that was the most resistant to the allelopathy of blady grass is mangium seedling. It was known from the analysis of variance test there was an interaction between the seedling and the concentration of blady grass allelopathy that effect the height, leaves number, living percentage ofseedlings

Allelopathic Observations in Rice (Oryza sativa L.) to Ducksalad (Heteranthera limosa)

More than 50 weed species infest drill-seeded rice in the U.S. and one of the most prevalent aquatic weeks is ducksalad (Heteranthera limosa). During the summer of 1988, a field experiment was conducted to identify rice accessions from the USDA/ARS rice germplasm collection for allelopathic effects to ducksalad. In this field experiment, 5,000 accessions were evaluated for allelopathic activity. Five to seven seeds of each rice accession were planted in hills about 75cm apart in two replications. Allelopathic activity was recorded as 1) radius of the area affected by allelochemical from the base of the rice plant and 2) percentage of weed control within the affected area. Ducksalad was rated at the panicle initiation stage of rice development. Of the 5,000 accessions that were evaluated, approximately 191 were identified as having evident allelopathic activity. The accessions that demonstrated allelopathic activity originated in 26 countries (Afghanistan, Argentina, Australia, Brazil, Columbia, Dominican Republic, France, India, Iran, Iraq, Israel, Italy, Japan, Malaysia, Mexico, Pakistan, Peru, Philippines, Portugal, Republic of Korea, People Republic of China, Soviet Union, Taiwan, Thailand, Turkey, and United States)

Impacts of Smooth Pigweed (Amaranthus hybridus) on Cover Crops in Southern Ontario

Amaranthus hybridus is a noxious weed in Ontario, with demonstrated allelopathic properties that can lead to decreased agricultural production. We tested the germination and growth of five cover crop species exposed to A. hybridus extracts, and to dried or fresh materials in soil. A germination index was calculated, and the dry weight of plant organs were measured to quantify responses to treatments. All species had reduced germination (≤29%) in 100% extract. Trifolium pratense had significant root weight reductions in extract (52%) and dried (72%) treatments, whereas shoot weight only decreased (48%) in dried treatment. Medicago sativa shoot weight decreased (52%) in 20g fresh treatment, while root weight decreased (62%) in dried treatment. Shoot weight of Raphanus sativus increased (32%) at mid-extract concentrations, while root weight increased (33%) only with dried treatment; however, both its shoot and root weight decreased (\u3e40%) in fresh treatment. Only the shoot weight of Lolium multiflorum increased (41% in 75% extract and 55% in dried treatment). Both Cichorium intybus shoot and root weights decreased (~50%) in fresh treatment. Crop responses to A. hybridus are complex, and material and species-dependant. Further testing in the field may provide a more comprehensive understanding of how to improve the management of A. hybridus