Showing papers on "Allelopathy published in 1986"

The Science of allelopathy

Abstract: Allelopathy: State of the Science FIELD OBSERVATIONS OF ALLELOPATHY IN DIVERSE ECOSYSTEMS: Growth Stimulation by Allelochemicals Adverse Impacts of Allelopathy in Agricultural Systems The Role of Allelopathy in Subtropical Agroecosystems of Taiwan Allelopathy: The Australian Experience Autotoxicity of Asparagus Officinalis TECHNIQUES FOR STUDIES OF ALLELOCHEMICALS AND THEIR MODES OF ACTION: Continuous Trapping Techniques for the Study of Allelochemicals from Higher Plants Bioassays in the Study of Allelopathy Isolating, Characterizing and Screening Mycotoxins for Herbicidal Activity Mechanisms and Modes of Action of Allelochemicals Allelochemical Mechanisms in the Inhibition of Herbs by Chapparel Shrubs CHEMISTRY AND POTENTIAL USES OF ALLELOPATHY: The Function of Mono and Sesquiterpenes as Plant Germination and Growth Regulators Polyacetylenes as Allelochemicals Qualitative and Quantitative Determination of the Allelochemical Sphere of Germinating Mung Bean Caffeine Autotoxicity in Coffea Arabica Allelopathic Activity of Rye Microbially Produced Phytotoxins as Herbicides - A Perspective Index

Allelopathic research of subtropical vegetation in Taiwan : III. Allelopathic exclusion of understory byLeucaena leucocephala (Lam.) de Wit.

Abstract: Leucaena leucocephala plantations in Kaoshu, southern Taiwan, exhibit, after several years of growth, a unique pattern of weed exclusion beneathLeucaena canopy. The pattern has been observed in manyLeucaena plantations in Taiwan and is particularly pronounced in the area where a substantial amount ofLeucaena litter has accumulated on the ground. Field data showed that the phenomenon was primarily not due to physical competition involving light, soil moisture, pH, and nutrients. Instead, aqueous extracts ofLeucaena fresh leaves, litter, soil, and seed exudate showed significantly phytotoxic effects on many test species, including rice, lettuce,Acacia confusa, Alnus formosana, Casuarina glauca, Liquidambar formosana, andMimosa pudica. However, the extracts were not toxic to the growth ofLeucaena seedlings. The decomposing leaves ofLeucaena also suppressed the growth of the aforementioned plants grown in pots but did not inhibit that ofLeucaena plants. By means of paper and thin-layer chromatography, UV-visible spectrophotometry, and high-performance liquid chromatography, 10 phytotoxins were identified. They included mimosine, quercetin, and gallic, protocatechuic,p-hydroxybenzoic,p-hydroxyphenylacetic, vanillic, ferulic, caffeic, andp-coumaric acids. The mature leaves ofLeucaena possess about 5% dry weight of mimosine, the amount varying with varieties. The seed germination and radicle growth of lettuce, rice, and rye grass were significantly inhibited by aqueous mimosine solution at a concentration of 20 ppm, while that of the forest species mentioned was suppressed by the mimosine solution at 50 ppm or above. However, the growth ofMiscanthus floridulus andPinus taiwanensis was not suppressed by the mimosine solution at 200 ppm. The seedlings ofAgeratum conzoides died in mimosine solution at 50 ppm within seven days and wilted at 300 ppm within three days. It was concluded that the exclusion of understory plants was evidently due to the allelopathic effect of compounds produced byLeucaena. The allelopathic pattern was clearly shown in the area with a heavy accumulation ofLeucaena leaf litter, which was a result of drought and heavy wind influence.

Allelopathic suppression of weed and nitrification by selected cultivars ofSorghum bicolor (L.) moench.

Abstract: Root exudates of 100 cultivars ofSorghum bicolor L. (Moench) were screened for their ability to inhibit seed germination and seedling growth ofAmaranthus retroflexus L. Exudates of some of the test cultivars were found to inhibit significantly seed germination and/or seedling growth ofA. retroflexus, and most of the inhibitory activity was found in neutral and acetone fractions of root exudates. Testing of aqueous extracts and decaying residues of four selectedSorghum cultivars (two toxic and two nontoxic through root exudation) revealed that all four cultivars significantly reducedA. retroflexus growth and nitrification processes with greater inhibition achieved by the toxic cultivars. This study suggests a potential biological control ofAmaranthus and nitrification by someS. bicolor cultivars.

Allelopathic influence ofSorghum bicolor on weeds during germination and early development of seedlings.

Abstract: The allelopathic interaction between sorghum [Sorghum bicolor (L.) Moench] and 10 species of grass and broadleaf weeds was investigated. Germination of weed seeds was slightly inhibited or stimulated, depending on species, when incubated in closed Petri dishes with germinating sorghum. Subsequent radicle and hypocotyl or coleoptile elongation of weeds was significantly inhibited by the germinating sorghum. For weeds interplanted with sorghum and grown under greenhouse conditions. The inhibitory effect on some weed species was still evident after 2 months of growth. Significant differences were found in the dry matter per weed plant grown in pots in proximity to sorghum vs. weeds grown in monoculture. Aqueous leachates from pots planted with sorghum alone or from a system in which sorghum roots protruded into water had strong allelopathic activity. These results indicate that water-soluble allelochemicals are produced by germinating sorghum seeds and that production of these substances continues during seedling growth.

Allelopathic Effects of Sweet Potatoes (Ipomoea batatas) on Yellow Nutsedge (Cyperus esculentus) and Alfalfa (Medicago sativa)

Abstract: Greenhouse and laboratory studies were con- ducted to determine the allelopathic potential of two sweet potato (Ipomoeat',atatas L (Lam)) cultivars, 'Regal' and 'SC 1149-19' YelloWlnutsedge (Cyperus esculentus L #3 CYPES) and alfalfa (Medicago sativa L) plants grown in soil from sweet potato field plots accumulated less dry matter than plants grown in soil from adjacent weedy plots Growth of yellow nutsedge and alfalfa plants-was also reduced when grown in a potting medium containing decomposing sweet potato plants in comparison to plants grown in potting medium alone When the sweet potato potting medium mixture was incubated at 25 C and tested weekly using an alfalfa growth bioassay, inhibition was high initially but decreased over time and was not observed after a 12-week incubation Aqueous methanol (50%)-soluble extracts of sweet potato periderm were inhibitory to yellow nutsedge root growth in vermiculite and alfalfa seed germination on filter paper Regal extracts were inhibitory to yellow nutsedge root growth at a concentration of 25 mg periderm extracted/ ml, but SC 1149-19 extract was inhibitory only at a con- centration eight times higher Similar differences between cultivars were observed with the alfalfa germination bioassay Preliminary separation of the Regal periderm extract by paper chromatography indicated the presence of phenolic compounds with a wide range of polarities Several of these UV-visible compounds were inhibitory to alfalfa germina- tion Additional index words Germination inhibitor, CYPES

Allelopathic influence of Tagetes- and Bidens-infested soils on seedling growth of certain crop species.

Abstract: Two naturally-occurring polyacetylene derivatives are found in Tagetes minuta L. and Bidens bipinnata L. which, when released into the soil, may affect crop growth. They are alpha- terthienyl in roots of T. minuta and phenylheptatriyne in leaves of B. bipinnata. Soil samples were collected from a lot where pure stands of the two weeds were found to be growing. Similar soil was also sampled for control purposes, where the two weeds did not occur. The effect of aqueous extracts, taken from the weed-infested soils, on seed germination of seven horticultural crop species was determined in the laboratory. Nine crop plant species were also grown in pots containing the sampled soil. The species were: carrot, cucumber, lettuce, maize, onion, radish, squash, sunflower and tomato. Seed germination was delayed by aqueous extracts from the weed- infested soils. Where soil was infested with Tagetes during the previous season, dry mass of top growth and plant height of all the test plants were greatly reduced. Soil fro...

Effects of soil-borne organisms on spring alfalfa establishment in an alfalfa rotation system.

Abstract: In 1983 and 1984, plots were established with various combinations of soil borne organisms to determine mortality factors that affect spring-seeded alfalfa seedlings in an alfalfa-following-alfalfa cropping system. In 1983, soil-borne insects caused a 43.8% decrease in seedling density 22 days after seeding, while soil-borne fungi reduced stand density by 40.5%. Stand density was reduced below a threshold level for reseeding at 61 days after seeding in plots with both pest groups occurring at natural densities. In 1984, fungi primarily stressed seedlings at emergence (6–9 days after seeding), while losses in stand density from insects occurred 15 days after seeding. Seedling height was reduced by stresses from natural populations of insects and soil-borne fungi during both years. Observations showed that the clover root curculio, Sitona hispidulus (F.), was the insect responsible for seedling loss in 1984. Alfalfa weevil, Hypera postica (Gyllenhal), damage was primarily from leaf feeding. Substantial numbers of dipteran larvae, Delia sp., were also found, but these larvae fed on decaying alfalfa roots from the previous stand. In both years, Fusarium spp. were the most frequently isolated fungi from diseased seedlings. Stresses from fungi and insects in 1984 significantly reduced dry weight yields by 49.5 and 19.0%, respectively.

The Chemistry of Allelopathy: Biochemical Interaction Among Plants

Abstract: Committee on Ocean Waste Transportation, Marine Board, Commission on Engineering and Technical Systems, National Research Council. National Academy Press, Washington, DC. 1984. 126p. $13.95. zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA In zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA 1981, the National Research Council conducted a symposium to assess the state of knowledge of ocean use for waste disposal. One of the results of the symposium was a request by the National Oceanic and Atmospheric Administration (NOAA) to the Marine Board to identify concepts for the processing and transport of domestic wastes for ultimate disposal in the ocean. The committee established by the Marine Board considered treated sewage sludge and effluent and its transport to, and release into, the sea from coastal USA communities. This book is the final report of the committee which included experts in ship and undersea pipeline engineering, municipal waste treatment design and operation, physical oceanography, environmental sciences, ocean geochemistry, ocean engineering, and naval architecture. The four major chapters include: “Wastewater Characteristics” which details concentrations of chemical constituents found in wastewater and sludges and primarily focus on Los Angeles’ Hyperion sewage treatment plant which discharges into the Southern California Bight; “Analysis and Design Objectives for Disposal Systems” which gives an excellent overview of ocean processing of sludge and wastewater constituents; “Transportation Systems: Comparative Cost Analysis and Research”, an economic study of several methods of transporting sludge to the ocean disposal site which considers self-propelled ships, barges-in-tow, articulated tug-barges, and rubber barges-in-tow and computes costs zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA as a function of travel distance; and “Application to Two Coastal Areas” which demonstrates how the information presented in the previous chapters can be applied to two ocean disposal cases: (i) a wide and shallow continental shelf, as found along the midAtlantic or Gulf states, and (ii) a narrow, rapidly deepening shelf, characteristic of the West Coast. This book will be of interest o anyone in the waste disposal field, but will be particularly useful to planners and those in government agencies involved with ocean disposal of wastes. As indicated in the Preface, the study reported here did not use risk assessment to evaluate the relative merits of ocean disposal vs. other options. However, the reader will find the book useful in understanding the scientific, engineering, and economic realities and constraints of ocean disposal of wastes and this knowledge can aid in the risk assessment process which ultimately must be conducted if ocean disposal is to become an acceptable disposal practice.-TERRY J. LOGAN, Agronomy Department, The Ohio State University, Columbus, OH 43210.

Effect of three weeds on the growth and mycorrhizal infection of black walnut seedlings

Abstract: The effect of unincorporated and incorporated litter and extracts of broom-sedge, fescue, and blackberry on the mycorrhizal development and growth of black walnut seedlings was investigated in two ...

Plant Germination and Growth Inhibitors From Ceratiola Ericoides and Calamintha Ashei (Herbicides, Allelopathy, Monoterpenes, Phenolics).

Abstract: As part of a chemical-ecological study of the Florida scrub community, Cevatiola eviooides (Empetraceae) and Calamintha aehei (Lamiaceae) were chemically investigated for natural products with possible allelochemical activities. The chromatographic separations and chemical investigations were guided by germination and radicle growth bioassays performed on seeds of commercial lettuce (Laotuoa eativa) and Sohizaohyvium soopavium, a native grass of the Florida sandhill community. From the dichloromethane extract of aerial parts of C. eviooides, 2',4'-dihydroxychalcone, the dihydrochalcones angoletin and 2',6'-dihydroxy-4-methoxy-3',5'dimethyldihydrochalcone, the flavanones 8methylpinocembrin, 6,8-dimethylpinocembrin and 7hydroxyflavanone were isolated along with the triterpenes erytrodiol and ursolic acid. Significant inhibition on S. soopavium radicle growth was observed with 6,8-dimethylpinocembrin when applied in a saturated aqueous solution of ursolic acid. From the active region of the ethyl acetate extract of C. eviooides, catechin, epicatechin, (A-2) dimer and