Showing papers on "Allelopathy published in 1979"

Allelopathy—An update

Abstract: The latest previous comprehensive review of allelopathy (Rice, 1974) covered research done primarily prior to 1973. There have been numerous reviews published in recent years on specific phases of allelopathy (see III), but most of them covered research results published primarily through 1972 also. This review has been restricted, therefore, largely to research conducted subsequent to 1972, except for background information and significant papers overlooked in previous reviews. There has been almost an exponential increase in the rate of publication of papers concerned with allelopathy. Research has been particularly active in relation to the roles of allelopathy in agriculture, forestry, phytopathology, patterning of vegetation, algal succession, and old-field succession. Our increasing knowledge of the conditions under which certain crop residues cause allelopathic effects to subsequent crops should enable us soon to guard against such effects. We are on the threshold of breeding crop plants that will inhibit the chief weeds in a given area through allelopathic action, and thus decrease the need for synthetic weed killers. Our understanding of allelopathic interactions of various plant species has already been used advantageously in reforestation, and future developments are very encouraging. Our increasing knowledge of allelopathy is aiding greatly in our understanding of many ecological phenomena, such as succession and patterning of vegetation. Evidence is mounting that inhibition of nitrification increases as succession progresses toward the climax vegetation, at least in many vegetation types. This leads to a decrease in the loss of nitrogen. Addition of inhibitors to arable lands to prevent nitrification has proved to be valuable in preventing loss of nitrogen and in increasing crop yields. There has been a rapid advance in our knowledge of mechanisms of action of known allelopathic compounds, at increasingly more fundamental levels. We have known for several years, for example, that some of these compounds inhibit uptake of various minerals, but have not known the mechanism of the action. Recent research indicates this may be due, at least in part, to inhibition of a plasma membrane ATPase that is involved with ion absorption. A thorough knowledge of mechanisms of action of allelochemics is essential to our overall understanding and appreciation of the field of allelopathy.

Allelopathy and its influence on the distribution of plants in an illinois old-field

Abstract: SUMMARY (1) A whole-community investigation of allelopathy in an old-field in Illinois was undertaken, by comparing bioassay results with association patterns in the field. (2) The seven most abundant species in the field were tested upon each other in nine commonly-used bioassays. Eight of the nine bioassays gave many cases of statistically significant inhibition, and strong phytotoxicity was exhibited by species which have not previously been suspected of being allelopathic and which show no readily-observable signs of allelopathy in the field. (3) Autotoxicity was found to be as severe as allotoxicity, indicating that the species have not evolved resistance to their own inhibitors. (4) When the distribution patterns of species in the field were statistically compared with the results of each of the bioassays in turn, no significant correlations were found. (5) It was concluded that the types of allelopathy which were tested by these bioassays were not demonstrably effective under field conditions, that perhaps any species can be shown to have allelopathic properties in bioassays, and that bioassays may, for many communities, have no ecological meaning.

Allelopathy of leafy spurge (Euphorbia esula).

Abstract: The allelopathic potential of leafy spurge (Eupborbia esula L) was investigated in the field and greenhouse Reductions in frequency and density of quackgrass [Agropyron repens (L) Beauvl and common ragweed (Ambrosia artemisiifolia L) were noted where leafy spurge had high densities in the field Field soil samples taken from areas of moderate and high leafy spurge densities inhibited tomatoes (Lycopersicon esculentum Mill) in the greenhouse Growth of seedlings was inhibited up to 60% when leafy spurge leaves, roots, or litter were incorporated into soil, but surface applied leafy spurge litter had no effect Growth inhibition was demonstrated for crabgrass [Digitaria sanguinalis (L) Scopl and tomato when 01 to 10% (w/w) of leafy spurge leaves or roots were added to soil Based on these studies we postulate that leafy spurge exhibits allelopathic characteristics which may result from the incorporation of dead or decaying plant material in soil Additional index words Plant litter, tomato, crabgrass

Comparison of the allelopathic potential of four marsh species.

Abstract: BONASERA, J., J. LYNCH, anid M. A. LECK. (Biol. Dept., Rider Coll., Lawreiieeville, New Jersey 08648). Comparison of the allelopathic potential of four miiarsh species. Bull. Torrey Bot. Club 106: 217-222. 1979.-A study of allelopathic potential of four species and three soils frolmi a New Jersey freshwater tidal mnarsh was imiade using four bioassay species. Ambrosia trifida leafancd Peltandra virginica leafancd petiole-extracts almost universally decreased germiiination and root growth of lettuce, radish, tomato, and cucumber. Ambrosia stern-extract inhibited growth but not germination. Bidens llaevis leafextract was generally inihibitory, but Bidens stemii-extract only inhibited germnination and growth of lettuce. Typha latifolia leaf-extract was inhibitory to growth, and to radish germination at 24 hrs. Typha rootancd rhizonme-extracts were the least inhibitory. The marsh soils from cattail, ragwveed, anld mnixed vegetation sites at 0 to 5 anid 5 to 10 cm had no effect onl germination of radish or cueumber. Cattail 0 to 5 em soil-extract enhanced cucumber growth at 72 hr aiid radish growvth at 48 hr. Of the bioassay species, lettuce was the most sensitive, radish ancd tomato someewhat less seiisitive, and cucumber the least sensitive.

The allelopathic potential of erica australis l. and e. arborea l.

Abstract: In laboratory tests aqueous extracts of aerial parts of Erica australis L. and E. arborea L. significantly inhibited root and hypocotyl growth of red clover (Trifolium pratense L.) but did not affect germination. Inhibition remained after chromatographic separation of the extracts. Using intact fresh leaves, stems, and flowers of E. australis and E. arborea, we also observed an inhibitory effect on root and hypocotyl growth. Dead leaves and flowers significantly inhibited the growth of red clover grown in soil in the greenhouse.

Allelochemic Effects of Leaf Extracts of Ambrosia trifida (Compositae)

Abstract: Aqueous extracts from leaves of giant ragweed reduced growth in sorghum seedlings, and reduced germination in sorghum and radish. Five phenolic compounds from these extracts were isolated and characterized, but not identified. Germination bioassays using these compounds demonstrated that each of the five depressed germination, and the depression related to concentration. It is suggested that the water-soluble allelochemics from giant ragweed contribute to any interference effect this weed may have on growth of associated species. A number of investigations of the distribution of vegetation in natural floristic communities have shown that allelopathy is an im- portant determinant in these plant associations (Rice 1974). Some of the recognized allelopathic plants found in these investigations are common weeds (Hamilton and Bucholtz 1955, Abdul-Wahab 1967, Wilson and Rice 1968, Parenti and Rice 1969, Neill and Rice 1971). However, the allelopathic potential of only a few weedy species of agronomic fields has been investigated. Bell and Koeppe (1972) reported giant foxtail (Setaria faberii Herrm.) caused allelo- pathic interference with the growth of corn. Both curled dock (Rumex crispus L.) and common milkweed (Asclepias syriaca L.) contain water-soluble inhibitors which may contribute to yield reduc- tions in grain sorghum (Einhellig and Rasmussen 1973, Rasmussen and Einhellig 1975). Several allelopathic mechanisms of velvetleaf on soybean and grain sorghum have been demonstrated (Colton 1978). These studies suggest that in arable fields allelopathy must be considered as part of the explanation of weed-induced reductions in plant growth and crop yields. Giant ragweed (Ambrosia trifida L.) is a common invader of waste areas and crop land of much of the United States (Muencher 1936). It germinates in early spring, stimulated by general soil

Allelopathic effect of some weeds of vegetable crops on the germination and early seedling growth of bajra pennisetum typhoideum

Abstract: Aqueous extracts of different parts of 11 weeds dominant in crop fields at Tirupati were examined for their allelopathic influence on seed germination and early seedling growth of bajra [Pennisetum americanum]. The investigation revealed that inhibitory substances were present predominantly in seed and shoot extracts, which caused strong inhibition of seed germination, leaf sheath elongation and root growth. From summary.

Allelopathic effect of some weeds of vegetable crops on the germination and early seedling growth of bajra

Abstract: Aqueous extracts of different parts of 11 weeds dominant in crop fields at Tirupati were examined for their allelopathic influence on seed germination and early seedling growth of bajra [Pennisetum americanum]. The investigation revealed that inhibitory substances were present predominantly in seed and shoot extracts, which caused strong inhibition of seed germination, leaf sheath elongation and root growth. From summary.

The allelopathic potential of Rhododendron macrophyllum in a western Cascades clearcut

Abstract: Let us know how access to this document benefits you.The allelopathic potential of Rhododendron macrophyllum in a western Cascades clearcut" (1979). Dissertations and Theses. Paper 2766. Rhododendron macrophyllum is a dominant species in.the shrub stage of secondary succession on burned and logged sites in the Tsuga heterophylla zone of the western Cascades of Oregon. A study was undertaken to determine if R. macrophyllum has the potential to inhibit the germination and growth of surrounding ~egetation through water-solub le toxins which. . are produced in its leaves and leached out of its litter by rainfall. Aqueous extracts of R. macrophyllum leaf litter significantly reduced germination and radicle growth in Btomus tectorum, ·Epilobitim ansustifolium, Picea sitChensis, ·pseudOtStiga·menzieSii, and·Tsu8a heterophylla. Osmotic pressure of the leaf extract solution was determined not to be a significant causative factor in the inhibition observed. Field studies showed four plant species to increase in frequency of presence with increasing distan~e from _1!. macrophyllum drip lines. Two species, both ericaceous, decreased in frequency of presence. Five species increased in density with increasing distance from R. macrophyllum drip lines, while only one species, which was ericaceous, decreased, It is postulated that these patte~s result fr~ the allelopathic influence of _1!. macrophyllum. Members of the Ericaceae are thought to either have a common response to environmental conditions or to be able to tolerate the toxins produced by members of thei~ family. iii ACKNOWLEDGEMENTS The author would like to extend his appr.eciation to his major advisor, Dr. Robert O. Tinnin, for his help and advice during the course of this investigation and for his helpful suggestions and criticisms in the preparation of this manuscript. Appreciation is likewise extended to the other members of my committee, Dr. Richard D. ~ocher and Dr. Richard B. Forbes, for their advice ~nd criti~isms and for the use of their laboratories and equipment during portions of this study. Appreciation is given also to Dr. Mary L. Taylor for use of her laboratory and equipment during a P?rtion of this s~udy. concerning the statistical analyses of my data. Thanks are given to Jim Sweet for his helpful laboratory measure-men ts. Gratitude is also expressed to the Crown Zellerbach Nursery in Aurora, Oregon for the donation of conifer seeds for use in this study. Finally, sincere appreciation is.extended to Kathryn A. Farr, who had to put up with me throughout the entire process.