Showing papers on "Allelopathy published in 1990"

An assessment of the allelopathic potential of Eucalyptus

Abstract: Previous studies have shown that various Eucalyptus species can yield allelopathic chemicals which may be effective in suppressing understorey vegetation. However, the techniques employed in many studies do not resemble natural ecological processes. This study used germination of Lolium and growth of Lolium, Lemna, Eucalyptus and Acacia to test for allelopathy. Extraction techniques mimicked typical daily rainfall rates upon quantities of foliage, leaf litter and bark litter that are typically encountered in forests; root leachates were obtained hydroponically; stemflow was obtained following rainfall; soils were leached with water; and volatiles from leaves were studied in an enclosed chamber. Fresh intact leaves caused little growth suppression, in contrast to coarsely chopped leaves and extracted leaf essential oils which were both highly suppressive. Whole leaf litter, shed bark and, especially, stemflow yielded suppressive leachates. Evaporative concentration of leachates in soils was demonstrated, which increased their inhibitory effect. It is apparent that allelopathy must be considered in relation to rainfall and the soil water balance. Decay was shown to reduce the allelopathic effects of leaf and bark litter leachates but some inhibitory chemicals remained after 5 months. It was concluded that allelopathy is likely to be a cause of understorey suppression by Eucalyptus species especially in drier climates.

Sagebrush and grasshopper responses to atmospheric carbon dioxide concentration.

Abstract: Seed- and clonally-propagated plants of Big Sagebrush (Artemisia tridentata var.tridentata) were grown under atmospheric carbon dioxide regimes of 270, 350 and 650 μl l−1 and fed toMelanoplus differentialis andM. sanguinipes grasshoppers. Total shrub biomass significantly increased as carbon dioxide levels increased, as did the weight and area of individual leaves. Plants grown from seed collected in a single population exhibited a 3–5 fold variation in the concentration of leaf volatile mono- and sesquiterpenes, guaianolide sesquiterpene lactones, coumarins and flavones within each CO2 treatment. The concentration of leaf allelochemicals did not differ significantly among CO2 treatments for these seed-propagated plants. Further, when genotypic variation was controlled by vegetative propagation, allelochemical concentrations also did not differ among carbon dioxide treatments. On the other hand, overall leaf nitrogen concentration declined significantly with elevated CO2. Carbon accumulation was seen to dilute leaf nitrogen as the balance of leaf carbon versus nitrogen progressively increased as CO2 growth concentration increased. Grasshopper feeding was highest on sagebrush leaves grown under 270 and 650 μl l−1 CO2, but varied widely within treatments. Leaf nitrogen concentration was an important positive factor in grasshopper relative growth but had no overall effect on consumption. Potential compensatory consumption by these generalist grasshoppers was apparently limited by the sagebrush allelochemicals. Insects with a greater ability to feed on chemically defended host plants under carbon dioxide enrichment may ultimately consume leaves with a lower nitrogen concentration but the same concentration of allelochemicals. Compensatory feeding may potentially increase the amount of dietary allelochemicals ingested for each unit of nitrogen consumed.

Allelopathy and autotoxicity in alfalfa: characterization and effects of preceding crops and residue incorporation.

Abstract: Alfalfa (Medicago sativa L.) is known to be both autotoxic and allelopathic. Greenhouse and laboratory experiments were conducted to determine if WL-316 alfalfa exhibits short-term autotoxicity and long-term autotoxicity and allelopathy. Long-term autotoxicity and allelopathy of alfalfa were verified at Urbana, IL, by comparing the germination and growth of alfalfa and sorghum [Sorghum bicolor (L.) Moench] on Flanagan silt loam (fine, montmorillonitic, mesic Aquic Argiudoll) previously cropped to alfalfa (alfalfa-soil) and sorghum (sorghum-soil). Short-term autotoxicity of alfalfa was investigated by studying the effect of incorporating its roots only and both roots and shoots on the germination and growth of alfalfa in alfalfa-soil and sorghum-soil. The data were further supported by a laboratory bioassay of seedling exudate and shoot leachate of alfalfa and sorghum. Plant height and fresh weight per plant of alfalfa and fresh weight per plant of sorghum were lower on alfalfa-soil than on sorghum-soil. Germination percentages of both alfalfa and sorghum and plant height of sorghum were unaffected by the preceding crop. The two soils differed in nutrient content, but fertility was high and should not have been limiting to the growth of either crop. As a result, allelopathic/autotoxic compounds in alfalfa-soil were implicated in the growth inhibition of the two crops. Soil incorporation of fresh alfalfa roots only or both roots and shoots reduced alfalfa emergence, plant height, and dry weight per plant. Primary effects of water-soluble inhibitory compounds from alfalfa shoot appeared to be on germination and radicle elongation, the latter being apparently more sensitive than the former. Alfalfa allelopathy seems to be more severe than autotoxicity. A flow diagram describes different kinds of allelopathy and autotoxicity and various situations that verify the existence of a particular kind of allelopathy or autotoxicity

Allelopathic and herbicidal effects of extracts from tree of heaven (Ailanthus altissima).

Abstract: Mature trees of Ailanthus altissima produce one or more potent inhibitors of seed germination and seedling growth. Inhibitor activity is highest in bark, especially of roots, intermediate in leaflets, and low in wood. Crude extracts of Ailanthus root bark and leaflets corresponding to 34 and 1 9 mg water extractable material/L, respectively, caused 50% inhibition of cress radicle growth. Ailanthus seeds also contain one or more inhibitors. These are bound within the seed by the pericarp but diffuse into water agar when the pericarp is removed. The inhibitor(s) could readily be extracted from Ailanthus tissues with methanol, but not dichloromethane, indicating polar characteristics. Ailanthus leaflets had highest inhibitory activity during expansion in spring, whereas activity of trunk bark peaked just before emergence of leaves. This pattern suggests transport of allelochemicals from bark into new leaves. A comparison of seven plant species for sensitivity to the inhibitor(s) from Ailanthus root bark showed little selectivity, although velvetleaf was somewhat more resistant. The inhibitor(s) from Ailanthus root bark exhibited strong herbicidal effects when sprayed pre- and postemergence on plants in soil in the greenhouse. Postemergence effects were striking, with nearly complete mortality of all species, except velvetleaf, at even the lowest doses tested. The results suggest the allelochemical(s) from Ailanthus may have potential for development as natural-product herbicides. PLANTS PRODUCE many compounds that have no apparent metabolic, physiologic, or struc

Allelopathic potential of glucosinolates (mustard oil glycosides) and their degradation products against wheat

Abstract: A number of glucosinolates and isothiocyanates were tested for their allelopathic potential against wheat. Most of the glucosinolates showed no activity against wheat, with the exception of glucobrassicin which was moderately active, as was sinapine thiocyanate. Isothiocyanates showed high activity against wheat germination and seedling growth. The most active compound, 2-phenethyl ITC completely inhibited wheat germination at 500 ppm. Allyl ITC showed high activity whereas other isothiocyanates tested were only moderately active. The data is discussed in relation to the possible use of some mustard species for effective weed control.

Evidence for allelopathy by tree-of-heaven (Ailanthus altissima).

Abstract: Ailanthus altissima (Mill.) Swingle contains one or more phytotoxic compounds in roots and leaves. Activity is higher in roots, where it occurs primarily in the bark. Powdered root bark and leaflets strongly inhibited growth of garden cress (Lepidium sativum L.) when mixed with soil in Petri dishes (ID50 values=0.03 g root bark, 0.6 g leaflet/dish). The toxic material was readily extracted by methanol but not dichloromethane. Pieces of root bark mixed with soil at 2, 1, and 0.5 g/pot reduced cress biomass in the greenhouse, whereas methanol-extracted root bark did not. The inhibitory effect ofAilanthus tissues in soil was short-lived (≤4 weeks in pots in greenhouse, ≤3 days in Petri dishes in laboratory). Inhibition by root bark was sometimes superseded by stimulation. FreshAilanthus root segments placed in or on soil reduced growth of nearby cress seedlings. Fine roots were more inhibitory than coarse, and inhibition became more pronounced with increased time of soil exposure to roots. Soil collected nearAilanthus roots in the field supported reduced radicle growth of cress compared to control soil. In contrast, stemflow fromAilanthus trees stimulated cress growth. The results suggest allelopathy caused by toxin exudation from roots may contribute to the aggressiveness and persistence ofAilanthus in certain habitats.

Allelopathy of crop residues influences corn seed germination and early growth.

Abstract: (...) Studies were conducted in which residues of corn, soybean [Glycine max (L.) Merr.], oat [Avena sativa (L.)], and mixed grass hay were extracted under N 2 gas or air. Organic debris was removed and half of each extract was filter sterilized. Corn seeds were incubated in the extracts for 96 h at 25°C. Percent germination, and lengths of coleoptile, radicle, and secondary roots were measured (...)

Bacterial degradation of juglone : Evidence against allelopathy?

Abstract: Recently, Schmidt (1988) isolated from the soil under Juglans nigra L. a bacterium capable of degrading juglone, the allelotoxin reputed to inhibit neighboring vegetation (Davis, 1928; Rietveld, 1983; Rietveld et al., 1983). Schmidt's report is noteworthy because it supports the previously hypothesized degradation ofjuglone by microorganisms (Fisher, 1978; Rietveld, 1983; Rietveld et al., 1983). However, Schmidt's (1988, p. 1561) conclusion that \"Rapid degradation ofjuglone and other suspected alMochemicals by soil bacteria make it unlikely that these compounds are important mediators of plant-plant interactions under natural conditions\" appears to us to be premature. In fact, the author might have argued equally convincingly that such specialized strains of soil bacteria confirm the frequent, if not continuous, presence of putative phytotoxins in the soil, and therein lend support to the allelopathic hypothesis. Neither contention is free of ambiguity. The phytotoxicity of allelochemicals in soil solution will depend on input and output rates as well as the effective concentration (Winter, 1961; Blum and Shafer, 1988). Schmidt's Pseudomonas J1 provides one output sink forjuglone. Juglone may be removed from the soil in numerous other ways, including, as Schmidt notes, soil physical and chemical processes. However, just as plants compete with microorganisms for nutrients (Pastor et al., 1984), the roots of plants inhibited by phytotoxins are potential competitors with microorganisms for the available phytotoxins (Winter, 1961; Hoffman and Lavy, 1978; Weidenhamer et al., 1987, 1989). The outcome of this competition may determine whether or not allelopathic effects are manifested. Therefore, bacterial affinities for juglone must be evaluated relative to target plant affinities and soil abiotic processes. Output rates themselves must be weighed against input rates of juglone into the soil solution (Winter, 1961). Influx may be a function of the amount of plant biomass (Rietveld et al., 1983), root exudation, litter decay, and precipitation throughfall, although in the case of juglone little is known in this regard. The actual available concentration of juglone will reflect the various input

Seasonal patterns of juglone in soil beneath Juglans nigra (black walnut) and influence of J. nigra on understory vegetation

Abstract: The allelopathic nature ofJ. nigra L. was investigated in several planted mixed hardwood stands located near Syracuse, New York. Concentrations of chloroform-extracted juglone from soil collected beneathJ. nigra was determined by thin-layer chromatography (TLC) and high-pressure liquid chromatography (HPLC). Soil juglone concentrations were corrected based on recovery of synthetic juglone added to soil. Soil juglone levels were high in the spring, decreased during the summer, and were high again in the fall. The quantification of juglone from soil by HPLC was found to be more accurate than by TLC. Regression analysis indicated that individual tree variation in soil juglone levels could not be explained by differences in soil moisture, pH, organic matter content, and texture. The results of juglone recovery experiments suggest that chloroform-extractable juglone does not persist in soil. Juglone degradation by microorganisms could only explain a portion of the juglone decline. Ordinations revealed that the herbaceous and woody vegetation beneathJ. nigra, in comparison to vegetation beneathAcer saccharum andQuercus rubra, is distinct in only one of the four stands studied. This vegetational difference did not appear to be a consequence of any strong allelopathic influences ofJ. nigra (Scheffe's method of contrast, chi-square analysis). The allelopathic nature of juglone under these field conditions is questionable.

Fate of plant-derived secondary metabolites in three moth species ( Syntomis mogadorensis, Syntomeida epilais , and Creatonotos transiens )

Abstract: Larvae of three moth species were compared with respect to strategies used to cope with secondary metabolites (allelochemicals) present in their diet.Syntomeida epilais is monophagous and accepted only oleander (which contains cardenolides, CG). CG were detected as stored products in the larvae and also in the faeces and exuviae. Pure CG (digoxin and gitoxin) which do not occur in oleander fed on oleander leaves were sequestered as the oleander CG.Syntomis mogadorensis is polyphagous: given a choice larvae avoided plants with a high load of allelochemicals. Upon shortage of preferred plants they ate a wide variety of plants which contain alkaloids, terpenes, or phenolics. Of these allelochemicals, alkaloids and CG were mainly recovered in the faeces and only minute fractions in the larvae.Creatonotos transiens larvae behaved similarly toSyntomis in terms of polyphagy and non-resorption. However, the larvae took up and stored pyrrolizidine alkaloids (PA) such as heliotrine selectively.Creatonotos is thus polyphagous (a generalist) but also a PA-specialist which exploits PA as defensive agents, as a morphogen for the male pheromone gland, and as a precursor for the male pheromone.

Allelopathic effects of Parthenium hysterophorus on germination and seedling growth of a few multi-purpose trees and arable crops.

Abstract: SUMMARY The allelopathic influence of Parthenium hysterphorus, a gregarious and ubiquitous weed, on four multi-purpose tree species – Acacia leucophloea, Casuarina equisetifolia, Eucalyptus tereticornis and Leucaena leucocephala and three agricultural crops – cowpea, sorghum and sunflower – were tested by germinating seeds of these species in composite leachate obtained from the leaves, stem and flowers of the weed species. Germination of seeds of all test species, arboreal and arable, was severely inhibited by the leachate. In the tree crops, the magnitude of injury was the same under extracts prepared from 2 or 4 ml of distilled water per g of plant tissue. Among the arable crops, sunflower was affected to a greater extent. While radicle and plumule elongation were unaffected in the tree crops and in sunflower, plumule was curbed to a greater extent than radicle in cowpea. In sorghum, only radicle growth was impaired. The inhibition of germination and seedling growth is attributed to parthenin, an unsat...

Studies on the allelopathic effects of some agroforestry tree crops of garhwal himalaya

Abstract: The allelopathic effects of Adina cordifolia, Alnus nepalensis, Celtis australis and Prunus cerasoides were tested by growing crops of Eleusine coracana, Glycine max and Hordeum vulgare on top soil, rhizosphere soil from the plantation of these trees, and on field soil either mulched with dry leaves or irrigated with aqueous leaf extracts of the agroforestry tree species. Germination percentage, shoot length, root length and dry matter production and pigment contents of crops were depressed by agroforestry tree crops. Maximum reduction in germination percentage, root-shoot length and dry matter production was obtained with experimental garden soil mulched with dry leaves of trees and by the effect of Adina cordifolia followed by P. cerasoides, H. vulgare proved most susceptible and E. coracana highly resistant to these tree-top interactions.

Germination of 2 legumes in leachate from introduced grasses.

Abstract: Kleberg bluestem [Dichmthium annuktum (Forsk) StaprJ and buffelgrass (Cmeluus ciIiur& L) may produce pbytotoxic cbemicals that inbibit germbtation and growth of legumes planted in s&g mixtures with grasses We determined the effects of leacbate from these introduced grasses on seed germination of Illinois bundleflower [Desmanthusilifuoens&(Michx) MacM] and partridge pea (Carsia~arciculoro Michx) Percent germination of Illinois bundleflower seeds on substrata moistened with Kleberg bluestem root or buffelgrass leaf leacbate was lower than that of seeds placed on substrata moistened with distilled water Buffelgrass root Ieacbate reduced germination of partridge pea more than did root leacbate from Kleberg bluestem or leafleacbate from Kleberg bluestem or buffelgrass Results of these laboratory experiments bulicate that field studies are warranted to determine the effects of buffelgrass on establishment of partridge pea and Illinois bundleflower in order to help land managers select the optimum combination of species for rangeland seeding

Comparative study of proteinase inhibitors in tropical root crops and survey of allelochemicals in the edible aroids.

Abstract: The distribution of the inhibitor between root and leaves of taro and within the stems of the aroids has also been studied The content of allelochemicals in five edible aroids is also considered in relation to the degree of apparency of the plant part and its resistance to parasites

Allelopathic inhibition of Cynodon dactylon (L.) pers. and other plant species by Euphorbia prostrata L.

Abstract: Field observations indicated thatEuphorbia prostrata strongly interferes withCynodon dactylon (L.) Pers. Analysis of some physical and chemical soil factors indicated that competition was not the dominant factor of that interference. Soil collected from underE. prostrata stands was very inhibitory to seed germination and seeding growth of some of the test species including C.Dactylon. This suggests the presence of inhibitory compounds in soil ofE. prostrata stands. Subsequent experiments showed that aqueous extract, decaying residues, and root exudates ofE. prostrata were inhibitory to most of the test species including C.Dactylon. Thus, it appears that allelopathy is the major component of the interference, with competition probably accentuating its effect. It also was found that allelopathy is an important component of the interference byE. prostrata againstAmaranthus retroflexus, Medicago sativa, andGossypium hirsutum.

Allelochemicals in soil from no-tillage versus conventional-tillage wheat (Triticum aestivum) fields.

Abstract: Putative allelochemicals found in the soil of no-tillage and conventional-tillage wheat plots near Stillwater, Oklahoma, were obtained by a mild alkaline aqueous extraction procedure, bioassayed to determine their biological activity, purified, and analyzed with a capillary gas chromatography-mass spectrometry-data analysis system. The most significant inhibition was found in bioassays of extracts from soil collected immediately after harvest in June, July, and August. No-tillage soils produced significant inhibition during the rest of the year also. Mass spectrometry showed fatty acids as the most abundant compounds. However, when bioassayed authentic samples of the five free fatty acids showed no significant biological activity toward wheat.

Natural inhibitors of germination and growth, V. Possible allelopathic effects of compounds from Thuja occidentalis.

Abstract: Abstract Volatile compounds which are released from fresh leaves of Thuja occidentalis inhibited germination of seeds of Amaranthus caudatus and Lepidium sativum. The volatile compounds were obtained by a vacuum method applied to the leaves, by direct analysis of the content of secretory organs and by solvent extraction of leaves. The bioactive compounds proved to be monoterpenes. The highest bioactivity were found for alcoholic compounds followed by ketones, esters and finally hydrocarbons. Non-volatile germination inhibitors which were ex- tracted with hot water were abscisic acid (3-4 µg/g fresh weight of leaves), and two oxidation products of thujone, 2-[2′-acetyl-l′-isopropyl]cyclopropylacetic acid (“Thujaketosaure”) and 3-isopropyl-5-oxohex-2-enoic acid. These compounds could also be prepared from thujone. The relationship of these compounds with possible allelopathic effects of Thuja occidentalis is discussed.

Sterilized culture of water hyacinth and its application in the study of allelopathic effect[s] on algae.

Abstract: After testing organic solid, organic liquid and inoraganic liquid culture media one by one and improving culture conditions, sterilized seedlings of water hyacinth (Eichhornia crassipes Solms.) with normal growth were established from axillary buds. A bioassay test was conducted to examine the allelopathic effect of the sterilized seedlings on Chlamydomonas reinhardtii. The results indicated that the extract from the water in which water hyacinth had been cultured under sterilized conditions still showed allelopathic effect. It means that the allelopathic compounds were exuded by water hyacinth itself, not by microbes living in its root zone.