Showing papers on "Allelopathy published in 1985"

The historical bases of the concept of allelopathy

Abstract: In the light of contemporary allelopathic research, the intuitively based statements of the early botanists stand up surprisingly well. The walnut tree is now understood to affect the growth of neighboring plants via juglone leached from the leaves, roots, and fruits.118 The replant or soil sickness problem of peach orchards has been related to the toxigenic breakdown of amygdalin, a constituent of peach roots.119 The declining yield of many crop species grown under continuous monoculture has been linked to the accumulation of allelopathic substances in the soil, especially through the mediation of microorganisms.120 Numerous plants cited by de Candolle as being injurious, such as Erigeron,121 thistle (Cirsium),122 flax (Linum),123 and various crucifers (such as Brassica nigra),124 have been found to posses marked allelopathic activity. Over fifty years before the discovery of rhizobia, de Candolle considered the excretory material of legumes to be beneficial to cereals.125 Modern reviews of allelopathy commonly credit de Candolle with an insight that was not equaled by the technology of his era.126 In fairness to his detractors, his toxin theory of plant interactions was largely the by-product of an outdated and misconstrued notion of plant nutrition. His critics and most earlier botanists had similarly erred in seeking a single factor responsible for plant growth, much as had the alchemists sought the legendary philosopher's stone. Taking all this into account and considering the forceful personality of Liebig, one can readily appreciate how, 130 years ago, Liebig's theories preempted and stifled those of de Candolle. Today, with modern techniques of plant physiology and soil biochemistry, allelopathy has been shown to be a real but subtle factor in the dynamics of natural and agricultural plant communities. It is unfortunate that the single-mindedness characteristic of previous centuries still persists. The dichotomy between allelopathy and competition is exacerbated by the inherited bias toward the nutritional model of plant interaction fostered by Liebig, and is accentuated in the fact that in modern nutritional studies it is still basically unnecessary to consider plant-plant chemical interactions and their concomitant effects, whereas in allelopathic investigations the converse is regarded as axiomatic. In summary, de Candolle should not be seen as “a prophet crying in the wilderness,” as Fisher would have it.127 The bases of de Candolle's concept of allelopathy were the dubious experiments of Macaire and his own obsolete theory of plant nutrition. Despite this, modern experimental work indicates that allelopathy is important in many plant interactions. De Candolle seems to have been right, at least in part—but for the wrong reasons.

Juglone concentration in soil beneath black walnut interplanted with nitrogen-fixing species.

Abstract: Juglone concentration was measured in soils collected under a 14-year-old black walnut (Juglans nigra L.) plantation containing plots of pure walnut and of walnut mixed with either autumn-olive (Elaeagnus umbellata Thunb.) or European black alder (Alnus glutinosa (L.) Gaertn.). Juglone concentrations declined with soil depth and distance from the walnut tree. Concentrations in autumn-olive-walnut plots were statistically lower than concentrations in European black alder-walnut or pure walnut plots. The concentration of juglone in soil in European black alder-walnut plots was apparently sufficient to cause the onset of black alder mortality.

Chemische Verteidigung der Lupinen: Zur biologischen Bedeutung der Chinolizidinalkaloide

Abstract: Quinolizidine alkaloids deter the feeding of herbivores (mammals, insects, molluscs), inhibit the growth and the development of bacteria and fungi and inhibit the germination of grass seeds and lettuce. Half-maximal inhibitor concentrations fall in the range between 0.5 and 15mM (= 0.01–0.3%). The actual concentrations of lupin alkaloids in the plant are between 5–200mmol/kg, i.e. much higher than the inhibitory concentrations. Since alkaloid-free lupins have a higher incidence of herbivory and disease, we assume that the biological function of lupin alkaloids is chemical defense besides minor roles as nitrogen transport and nitrogen storage compounds.

The negative effects of litter of parent plants of Cirsium vulgare on their offspring: autotoxicity or immobilization?

Abstract: It is shown that litter of flowering plants of Cirsium vulgare inhibits the growth of seedlings of the same species at concentrations as low as 0.4% (g litter/g soil). The inhibition of growth cannot be fully compensated by adding nutrients, which indicates that autotoxicity may occur. It must be concluded, however, from an analysis of the results that immobilization of nutrients by microorganisms is the main cause of growth reduction if litter is added to the soil. In a field experiment under nutrient rich conditions plant litter did not affect germination, survival or growth of seedlings. The hypothesis is put forward that under conditions of nutrient deficiency and at high population densities, immobilization of nitrogen by Cirsium vulgare litter may influence plant growth. Results are discussed in relation to those of Stachon and Zimdahl (1980) and Wilson (1981) who claimed allelopathy for the related Cirsium arvense.

Allelopathic effects ofCitrus aurantium L. : II. Isolation, characterization, and biological activities of phytotoxins.

Abstract: In an earlier work, we found that the failure of herbaceous plants to grow under sour orange was mainly due to an allelopathic mechanism. Four nonvolatile inhibitors were isolated by paper chromatography. Color reactions of all the inhibitors indicated that they are phenolic in nature. On the other hand, five volatile inhibitors were detected by gas chromatography, four of which were terpenes. All inhibitors reduced seed germination and/or seedling growth ofAmaranthus retroflexus.

Induction of Hydrolases by Allelochemicals and Host Plants in Fall Armyworm (Lepidoptera: Noctuidae) Larvae

Abstract: The influence of allelochemicals and host plants on two hydrolases, α -naphthyl acetate ( α -NA) esterase and styrene oxide hydrolase, was investigated in the fall armyworm, Spodoptera frugiperda (J. E. Smith). The α -NA esterase was induced by a range of allelochemicals. Celery, potato, and parsley were also active in inducing the esterase, whereas a number of other host plants had no significant effect. Styrene oxide hydrolase was moderately induced by indole 3-carbinol, peppermint oil, and phenobarbital, but none of the host plants showed any inductive effect.

Inhibition of seedling growth of crop species by recirculating root exudates ofBidens pilosa L.

Abstract: The allelopathic effects of root exudates ofBidens pilosa L. on seedling growth ofLactuca sativa L.,Phaseolus vulgaris L.,Zea mays L., andSorghum bicolor (L.) Moench were studied using a root exudate recirculating system that allows continuous exposure of crop plants to allelopathic chemicals. This system maintains an undisturbed rhizosphere and eliminates competition and physical contact between the donor and acceptor plants. Comparison of responses to hydrophobic and hydrophilic root exudates is made possible by removal of hydrophobic compounds using XAD-4. Treatments consisted ofB. pilosa, B. pilosa with an Amberlite XAD-4 resin column attached to the donor pot to remove hydrophobic allelochemicals, and a donor pot without weeds.B. pilosa significantly inhibited seedling growth of all crop species tested. The crop species varied in response to the root exudates, withL. sativa being most sensitive. Larger and olderB. pilosa plants caused greater inhibition of seedling growth ofL. sativa andP. vulgaris than did smaller (younger)B. pilosa plants.B. pilosa with XAD-4 caused significantly less inhibition to all crop species, exceptZ. mays, thanB. pilosa without XAD-4, indicating that the hydrophobic exudates played an important role in the allelopathic growth inhibition. Variability in species response toB. pilosa with and without XAD-4 was probably due to differences in sensitivity to hydophobic and hydrophilic allelochemicals.

Allelopathic effects ofCitrus aurantium L. : I. Vegetational patterning.

Abstract: Field observations on undisturbed stands of sour orange revealed thatCynodon dactylon, Chenopodium album, Avena sativa, andAmaranthus retroflexus were not able to grow normally and complete their life cycles under its canopies, although the same species grow well under adjacent trees of date palm. Investigations revealed that the failure of the test species to grow normally under sour orange was not due to competition for light, moisture and minerals or to differences in soil texture or pH. Soil under sour orange trees drastically reduced seed germination and/or seedling growth of test species. Aqueous extracts, decaying materials, and volatile compounds of senescent and nonsenescent sour orange leaves were found to inhibit seed germination and/or seedling growth of test species. Therefore, allelopathy appeared to be the basic factor responsible for the reduction in plant growth with competition propably accentuating its effects.

Effect of gamma irradiation on allelopathic potential of Sorghum bicolor against weeds and nitrification

Abstract: The effect of low doses of gamma irradiation on the allelopathic potential ofSorghum bicolor against weeds and nitrification was investigated. The results revealed that all test doses (500, 1000 and 1500 rad) significantly increased the allelopathic activity of root exudates, aqueous extracts, and decaying residues aganst seed germination and seedling growth ofAmaranthus retroflexus. The results also indicated that all test doses stimulated the allelopathic potential of aqueous extracts and decaying residues against nitrification activity. The possible application of this approach in biological control is briefly discussed.

Allelopathic effects of Trichostema lanceolatum (Labiatae) in the California annual grassland

Abstract: (1) Trichostema lanceolatum, a common herb in the California annual grassland, contains 2-9% volatile essential oil in its fresh foliage. Vapours and aqueous extracts from its leaves have been shown to inhibit germination and growth of other plants in vitro. The present study evaluated the potential of T. lanceolatum to restrict plant growth in the field. (2) Dry soil charged with T. lanceolatum volatiles in the laboratory reduced radicle elongation of seeds, but dry seeds and dry soil exposed to volatiles under T. lanceolatum plants in the field did not show appreciable inhibition. (3) Trichostema lanceolatum throughfall from early-season rains was, at most, only weakly toxic. Soil at the base of T. lanceolatum plants was not rendered toxic by throughfall and stemflow from the first autumn rain. (4) Water and ether extracts of dead, brown T. lanceolatum leaves were very toxic in bioassays in Petri dishes, but similar leaves mixed with soil had little allelopathic effect. (5) Trichostema lanceolatum seedlings were no more resistant to volatiles of T. lanceolatum essential oil than seedlings of other annual grassland species. (6) The allelopathic potential of T. lanceolatum under natural conditions appears to be low. This conclusion is surprising since both green and dead, brown leaves from it were much more inhibitory in laboratory bioassays than were leaves and litter from Salvia leucophylla, a species previously reported to be strongly allelopathic.

Allelopathic effects of Parthenium hysterophorus L. leachates and extracts on Brassica campestris L.

Abstract: Aqueous and organic leachates and organic extracts fractionated from leaves and inflorescence of Parthenium hysterophorus exhibited allelopathic effects on Brassica campestris. A marked reduction in leaf cell survival and chlorophyll content indicated toxicity of the leachates and extracts. Germination and seedling growth was also inhibited.

Defensive stratagems of plants, with special reference to allelopathy

Abstract: The green plant has evolved an array of defences to ameliorate the effects of stresses in its environment. Allelopathy, biochemical interactions between plants, plays a role in plant defence but recent work suggeststhat some compounds which act as allelochemicals may also be effective in the defence of plants agamst other organIsms. Some examples of allelopathy in associations of crop and weed species are discussed in this context.

Allelopathic Potentials of Larix leptolepis (S. et Z.) Gorden on Germination and Seeding Growth of Selected Species

Abstract: A number of field surveys have been performed in larch (Larix leptolepsis) forest floor in which any seeding of this species never find ther. In laboratory work, aqueous extracts from leaves, roots and stems of larch were provided and used to bioassay. Among them, germination and seedling growth of selected species were the most inhibitory in leaves extracts. Though germiation percentage of a species showed high compared with control, its dry weight after a given period grown were clearly low. The results due to be considered by allelopathic effect. And syringic acid and p-hydroxybenzoic acid were identified by HPLC from larch leaves. It is assumed that these phenolic acids affect on other species as allelochemicals of larch.