Showing papers on "Allelopathy published in 1980"

Allelopathic activity of Canada thistle (Cirsium arvense) in Colorado.

Abstract: Low species diversity accompanied high populations of Canada thistle [Cirsium arvense (L.) Scop.] . Two perennial grasses and two rushes grew with Canada thistle; annual plants did not. Canada thistle litter, ground roots, and ground foliage added to soil in greenhouse bioassay tests reduced growth of redroot pigweed (Amarantbus retroflexus L.) and green foxtail [Setana viridis (L.) Beauv.] more than cucumber (Cucumis sativis L.) or barley (Hordeum vulgare L.). The addition of nutrients did not mask the toxic effect. Ethanolic extracts of Canada thistle roots and foliage were similar in their ability to reduce radicle growth of barley, cucumber, green foxtail, and redroot pigweed in petri dish studies. There was no significant difference between water controls and controls adjusted to the average pH and osmotic potential of the extracts. Germination of barley and cucumber seed was not affected. Comparisons between ethanolic extractions and soil incorporation of plant residues with presumably non-allelopathic plants revealed that cucumber and barley extracts reduced redroot pigweed radicle growth whereas barley and green foxtail extracts increased green foxtail radicle growth. These effects were not observed when these plant residues were mixed in soil. Additional index words. Plant residue, toxic extracts, weed ecology.

The Allelopathic Effect of Yellow Nutsedge (Cyperus esculentus) on Corn (Zea mays) and Soybeans (Glycine max)

Abstract: Four greenhouse experiments were conducted to study the effects of plant residues and extracts of yellow nutsedge (Cyperus escu - lentus L.) plant residues on the growth of corn (Zea mays L.) and soy- beans (Glycine max (L.) Merr.) . At equal concentrations, tuber resi- dues reduced the dry weight of corn and soybeans more than foliage residues. As the concentration increased, growth decreased, affecting soybeans more than corn. Soybean growth was significantly reduced by the addition of tuber extracts. At a constant residue concentration, in- creasing the percentage of sand in the soil mixture reduced the growth of corn and soybeans. Growth inhibition was greatest when tuber residues were in contact with the corn or soybean seed. We conclude that extracts and residues of yellow nutsedge have an allelopathic effect on corn and soybeans under greenhouse conditions. Additional index words. Plant residues, decomposition, plant inter- ference.

Allelopathic mechanisms of velvetleaf (abutilon theophrasti medic., malvaceae) on soybean

Abstract: Sampling in.a soybean field established that presence of velvetleaf (A. theophrasti) weeds interfered with soybean production. Number of soybean pods and number of pods/stem were significantly lower in transect segments adjacent to velvetleaf plants. In bioassays for phytotoxicity of velvetleaf, several dilutions of aqueous extracts from fresh field-collected leaves depressed germination of radish seeds and inhibited growth of soybean seedlings. Seed germination bioassays from eluates of chromatograms developed in one dimension showed that two of three bands containing phenolic compounds were inhibitory to radish seed germination. Soybeans inhibited by aqueous velvetleaf extracts had increased diffusive resistance, suggesting partial stomatal closure. Inhibited plants also gave evidence of water stress, with leaf water potentials often as low as -20 bars and reduced water content, when compared with controls. Quantification of chlorophyll on a leaf area basis showed that chlorophyll of inhibited plants was below controls. These data demonstrate the allelopathic potential of velvetleaf and suggest that interference with water balance and chlorophyll content may be two mechanisms of inhibitory action of toxins present in the leaves of velvetleaf. SEVERAL INVESTIGATORS have shown that allelopathy may be a part of weed and crop interactions. Bell and Koeppe (1972) reported that allelopathic effects of foxtail (Setaria faberi Herm.) contributed to reduction in corn (Zea mays L.) growth. Curled dock (Rumex crispus L.) and common milkweed (Asclepias syriaca L.) may have inhibitory effects on crop species because of water soluble phytotoxins in the leaves (Einhellig and Rasmussen, 1973; Rasmussen and Einhellig, 1975). Putnam and Duke (1978) hypothesize allelopathy may be a factor in increases in dominance by certain weeds in a variety of crop ecosystems. In addition to investigations implicating the allelopathic potential of several weeds on field crops, a number of weedy species release phytotoxins which influence the vegetational composition of natural communities, both in space and in time (Abdul-Wahab and Rice, 1967; Wilson and Rice, 1968; Parenti and Rice, 1969; Neill and Rice, 1971). Thus, the concept that some plants may adversely affect other plants through biochemical products is a known component of plant interactions. Velvetleaf (Abutilon theophrasti Medic.) is an annual weed of wide distribution in eastern United States and the more mesic regions of the prairie states. It is an introduced species, which is difficult to control in soybean fields because preplant and preemergence herbicide

C10-Polyacetylenes as allelopathic substances in dominants in early stages of secondary succession.

Abstract: cis-Dehydromatricaria ester (cis-DME) inSolidago altissima, andcis-matricaria ester (cis-ME),trans-matricaria ester (trans-ME), andcis-lachnophyllum ester (cis-LE) inErigeron spp. show strong growth inhibitory effects on other plants. Thecis- andtrans-DMEs were found in soil at the border ofS. altissima communities in concentrations that were inhibitory to test plants. Among four species ofErigeron, the most dominant plant,E floribundus, showed the highest concentrations of the esters. From the results of our experiments, we conclude that these polyacetylenes are probably allelopathic substances with ecological importance.

Allelopathic potential of ground cover species on Pinus resinosa seedlings.

Abstract: Water extracts of foliage ofAster macrophyllus, Lonicera tatarica, Solanum dulcamara, Solidago gigantea, Prunus serotina, andRubus idaeus var.strigosus, collected from the ground vegetation of a red pine (Pinus resinosa Ait.) plantation, were tested for potential allelopathic effects on seed germination, radicle elongation, and growth of red pine seedlings. Seed germination was not significantly affected by extracts, but radicle elongation of newly germinated seeds was reduced by up to 48% compared to controls. All extracts variously inhibited height growth, formation of secondary needles, and dry weight increment of young red pine seedlings during a seven-week experiment. Total dry weight of seedlings treated with Lonicera extract was only 46% that of control plants. Phosphorus concentration in needles treated with Lonicera or Solidago extracts was significantly lower than that of controls. Growth inhibition was not mediated by pH effects or osmotic potentials of the extracts. The data suggest that allelopathic inhibition of red pine is possible, but additional field experiments are needed to evaluate the significance of allelopathy in red pine plantations.

Phenolic inhibitors in Erica australis L. and in associated soil

Abstract: Fifteen phenolic compounds were identified in methanolic extracts obtained from flowers, leaves, stems, and roots ofErica australis L. and the associated soil. It is possible that the compounds identified may be connected with allelopathic phenomena.

Inhibition of protein synthesis in lettuce (Latuca sativa L.) by allelopathic compounds

Abstract: The effects of ferulic, cinnamic, and ellagic acids on the development of roots and protein synthesis in lettuce seedlings (Latuca sativa L., variety of Black Seeded Simpson) are reported here. Both ferulic and cinnamic acids were found to inhibit protein synthesis of the seedlings either when added from the beginning of the germination period, or when added for a short period of time to seedlings which had already germinated under control conditions. Ellagic acid, at the same pH and osmotic concentrations as the effective inhibitors, was completely ineffective in inhibiting either growth of roots or protein synthesis. It is shown that utilization of [14C] amino acid incorporation into seedlings appears to be a sensitive, reliable, and appropriate indicator of allelopathic inhibition of plant growth. Utilizing this method, it should be possible to determine if the effect on protein synthesis by putative allelopathic compounds is a general phenomenon and may, in turn, help to elucidate the role of these compounds.

Inhibition of turnip (Brassica rapa) seed germination by velvetleaf (Abutilon theophrasti) seed.

Abstract: The allelopathic potential of germinating seed of velvetleaf (Abutilon tbeopbrasti Medic.) was established in a laboratory study with germinating seed of turnip (Brassica rapa L. 'Purple Top'). Twoday-old velvetleaf seedlings inhibited radicle growth of germinating turnip by 17% at 24 h after both were placed in the same petri plate. Alcoholic and aqueous extracts of velvetleaf seed, however, seriously inhibited germination of turnip seed. The extract of velvetleaf seed was fractionated by ion-exchange chromatography into acid, basic, and neutral fractions. Most of the allelopathic activity was located in the acid fraction, which includes the plant phenolics. The basic fraction (amino acids) inhibited radicle growth of turnip by 18% after 48 h. The amino acid profile of velvetleaf seed extracts is presented and discussed, because this fraction has previously been implicated as the allelopathic fraction. Additional index words. Free amino acids, allelopathy, bioassay.

Allelopathic activity of camelina sativa (l.) crantz in relation to its phyllosphere bacteria

Abstract: SUMMARY In the presence of phyllosphere bacteria, aqueous washings of foliage of Camelina sativa stimulate early growth of several species of higher plants. At least two bacteria can promote the observed effects, however, suitable substrates for bacterial activity may be limited to cruciferous plants. The stimulatory principle is produced rapidly by bacterial activity and is probably an organic chemical produced by bacterial degradation of more complex compounds commonly found in the Cruciferae.

Allelopathic effects of Pakistani weeds: Euphorbia granulata Forssk.

Abstract: The aqueous extract of Euphorbia granulata Forssk., prepared in Hoagland's nutrient solution; and underlying soil significantly inhibited germination and radicle growth of Dichanthium annulatum, Cynodon dactylon, Setaria italica, Pennisetum americanum, Euphorbia pilulifera, Oxalis corniculata and Lactuca sativa invariably in laboratory bioassays. Artificially decomposed E. granulata litter in a nutrient medium significantly reduced germination and fresh and dry weight of the aforementioned test species. The toxins affected germination and growth independently. The local dominance of this weed over its counterparts was primarily due to allelopathy, and it is therefore suggested that its litter must be removed from the fields during weeding.

Allelopathy and Autotoxicity in Three Eastern North American Ferns

Abstract: the other to physical and biological conditions, and so limit the success of the species. Although environmental (abiotic) conditions are extremely important, biotic conditions, particularly those created by the sporophytes or gametophytes, may also be of critical importance in the establishment of new individuals of the same or another species. Therefore, these factors may regulate both population density and community composition. Chemical inhibition of one plant by another, or allelopathy, has been known for over a century (Muller, 1966) and has been much studied in flowering plants and conifers. The phenomenon of antibiosis is also well known to microbiologists. However, relatively little research has been devoted to plant inhibitors produced by non-seed plants, other than microorganisms (Rice, 1967). Bohm and Tryon (1967) reported that many species of ferns produce phenolic compounds. They examined 46 species for the presence of hydroxylated cinnamic and benzoic acids and found a basic complement of cinnamic acids (p-coumaric, caffeic, and ferulic) in the ferns they tested. Also generally present were p-hydroxybenzoic, protocatechuic, and vanillic acids. Sinapic, syringic, and o-coumaric acids were reported to be less common. In a follow-up study, Glass and Bohm (1969) found similar phenolic compounds in 46 additional species. The presence of a basic complement suggests that the well established pathways of phenolic metabolism in the seed plants also function in ferns. Many of the phenolic compounds found in ferns are known to be allelopathic in many species of higher plants, either directly or indirectly, such as after microbial decomposition (Rice, 1974). Most phenolic acids are at least slightly soluble in water. With the increasingly acidic rainfall in the northeastern United States (Likens et al., 1970; Bormann & Likens, 1977), weak organic acids such as the phenolics may be leached quite readily either from the leaves during the growing season or from senescent plants. A wide variety of organic and inorganic sub