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Stress modification of allelopathy ofHelianthus annuus L. debris on seedling biomass production ofAmaranthus retroflexus L

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Abstract

When added to soil,Helianthus annuus debris from plants grown under various nutrient stresses in the greenhouse and field had a significant negative effect onAmaranthus retroflexus seedling dry weight production. The regression models for dry weight versus total phenolic compounds and the variation in N, P, and K contents of theHelianthus debris were significant. It was possible to partially simulate debris inhibition ofA. retroflexus seedling dry weight production when chlorogenic acid alone was added to the soil instead ofHelianthus debris. The inhibition ofAmaranthus growth byHelianthus debris and chlorogenic acid was not evident when nutrient solution was applied to the soil.

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... Ferulic acid and hydroxybenzoic acid when added to soil resulted into inhibition of phosphorus uptake by plants [46]. Chlorogenic acid when added to soil inhibits the uptake of phosphorus in Amaranthus retroflexus L. However, addition of nutrients NPK to soil nullifies the effect of chrorogenic acid [47]. Nitrogen and phosphorus influence the phytoxicity caused by vanillic and p-oumaric acid [48]. ...
... Results of Helianthus annus L debris and chlorogenic acid bioassay suggests that nutrients in debris act differentially in modifying effects of phenolic compounds on seedling growth of Amaranthus retroflexus L than do nutrient added to soil as solution. It suggests Table 3. Sodium, potassium, calcium and chloride (%) in leaves of (25 days old) wheat (Triticum aestivum L.), 15 days after leachate treatment of Jatropha curcas L. that nutrient status of soil may have an impact on allelopathic effects [47]. Salicylic acid treated soybean seedlings showed higher leaf diffusive resistance, lower transpiration and water potential suggesting the interference of allelochemicals with plant water relations as one of the mechanisms that inhibit plant growth. ...
... In field experiment, the variety Masuran followed by the variety Kaluheenati showed the greatest reduction in DW accumulation of BYG. Several researches showed that phytotoxicity of the chemicals as well as the amount of chemical production are highly depend on many factors, such as agronomic and management practices, environmental factors, biotic and abiotic stresses, chemical and biological properties of soil, plant growth and development stage, plant origin etc. (Hall et al., 1993, Mwaja et al., 1995, Seigler, 1996.Not only that Lovett and Ryuntyn (1992) suggested that allelopathy may be part of a whole network of chemical communication between plants, and between plants and other organisms, and that such communication may contribute to plant defense. The inconsistent results of these three experiments may partly due to the complex nature of allelopathic effects under natural conditions. ...
... Our study, along with the SDH, emphasizes the importance of incorporating the fundamental difference between specialist and generalist herbivores when examining evolutionary impacts of altered specialist-generalist herbivore composition on invasive plants. There is increasing evidence that defensive secondary metabolites, including chlorogenic acid, may also possess allelopathic attributes, through which plants may benefit from competition with others (Hall, Blum, & Fites, 1982, 1983Zheng et al., 2015). Future studies should further examine whether enemy reassociation can influence the competitive ability of invasive plants by altering the production of defence compounds with allelopathic ability and the consequent dynamics of the invaded communities. ...
Article
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The shifting defence hypothesis (SDH) predicts that after invasive plants are introduced to new ranges, they will evolve reduced resistance to specialist herbivores and increased resistance to generalist herbivores because they can escape from specialists but are still attacked by generalists in their nonnative ranges. For this to be true, the subsequent introduction of native specialist herbivores should reverse the above evolutionary processes, but evidence collected so far is scarce. Here, we address this research gap by comparing resistance to specialist and generalist herbivores and resistance‐related traits in the invasive plant Ambrosia artemisiifolia from five populations with about a decade history of infestation by the accidentally introduced native specialist leaf beetle Ophraella communa (infested populations), and three populations without such infestation history (uninfested populations). In common garden experiments, the specialist O. communa performed better on uninfested populations than on infested populations, whereas two generalist insects, Spodoptera litura and Helicoverpa armigera, performed better on infested populations. Chemical analyses showed that plants from infested populations had lower concentrations of chlorogenic acid, an antigeneralist secondary compound that can attract O. communa. Furthermore, across mother plants from all populations studied, chlorogenic acid content was negatively correlated with larval growth of S. litura and positively correlated with that of O. communa. Finally, quantitative defence traits did not differ between infested and uninfested populations. Although our results are most consistent with rapid evolution caused by enemy reassociation, we cannot exclude the possibility that observed differences in resistance result from multiple introductions or selections from other environmental factors. Synthesis. These results suggest that reassociation with a specialist herbivore from the native range may result in a rapid evolution of increased resistance to specialist herbivores and reduced resistance to generalist herbivores in the introduced range, which is likely to be mediated by the reduced production of secondary chemicals that can deter generalists while attracting the introduced specialist. This study supports the shifting defence hypothesis (SDH) from a new viewpoint, emphasizing the importance of incorporating the impacts of both specialist and generalist herbivores when evaluating the long‐term control effects of classical biological control programmes.
... Allelopathic potential of sunflower weed control has been reported in wild as well in its cultivars viz., 'Ramsum HS-52', 'Peredovik', 'Hybrids 201.,' '8947' (720, 136). In green house studies, sunflower'Russian Mammoth' residues reduces both, seed germination and biomass of weeds (93,94). The aqueous extracts as well as growing plants inhibit seed germination and seedling growth of Abutilon theophrasti, Datura stramonium, lpomoea spp. ...
... Chemical analyses using HPLC indicated the presence of several phenolic compounds in water extract of residues from sunflower genotypes. These allelochemicals suppress the germination and seedling growth of succeeding crops viz., wheat, mustard, mungbean, blackgram, soybean, sorghum and pearl millet and amaranthus weeds (2,9,10,11,12,16,21,34). These phenolic acids inhibits the ion uptake, chlorophyll biosynthesis, cell membrane stability, protein and hormone biosynthesis, cell division and changes ultra-structural components of cells (32). ...
Article
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We studied the allelopathic effects of sunflower on the succeeding mungbean crop and also identified and quantified the allelochemicals present in different plant parts of sunflower using HPLC. Phenolic compounds present in leaves of sunflower were : Chlorogenic acid (18.53±0.66 mg/100 g) > trans-ferulic acid (17.96 ±1.15 mg/100 g) > caffeic acid (17.32±1.59 mg/100 g) > vanillic acid (15.34±1.07 mg/100 g), while stem contained trans-ferulic acid (17.92±1.57 mg/100 g) > chlorogenic acid (16.31±0.95 mg/100 g) > vanillic acid (15.15±0.91 mg/100 g) and root contains only trans-ferulic acid (13.6±1.2 mg/100 g). The seed yield of mungbean was significantly higher in fallow-mungbean rotation (716 kg/ha) than in sunflower-mungbean sequence (593 kg/ha). Among the sowing periods, the crop sown on June 14 gave significantly higher seed yield (904 kg ha⁻¹) than other sowing dates except June 21 (837 kg ha⁻¹). The seed yield of mungbean in fallow-mungbean rotation sown on June 14 was 1038 kg ha⁻¹ than sunflower-mungbean rotation sown on June 14 (770 kg ha⁻¹). © 2017, International Allelopathy Foundation. All rights reserved.
... Allelopathic potential of sunflower weed control has been reported in wild as well in its cultivars viz., 'Ramsum HS-52', 'Peredovik', 'Hybrids 201.,' '8947' (720, 136). In green house studies, sunflower'Russian Mammoth' residues reduces both, seed germination and biomass of weeds (93,94). The aqueous extracts as well as growing plants inhibit seed germination and seedling growth of Abutilon theophrasti, Datura stramonium, lpomoea spp. ...
... Phenylpropanoid was a member of phenolic compound, which pertained to plant secondary metabolites. For example, Hall et al. found that the phenolic content was stimulated by an increase in nutrient stress in Helianthus annuns [40]. Similar phenomenon occurred in Tageteserecta when suffering from water stress with a [41]. ...
Article
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Phosphorus is one of the most important macronutrients that is required for plant growth and development. However, stress under low-P conditions has become a limiting factor that affects crop yields and qualities. Plants have developed strategies to cope with this, while few genes associated with low-P tolerance have been identified in soybean. Genome-wide analyses were performed on the roots and leaves of a low-P-tolerant accession and a low-P-sensitive accession which were identified by hydroponic experiments under different P treatments. Through comparative analyses on the differently expressed genes, we explored 42 common genes that were highly correlated to low-P stress. The functional classification of these genes revealed 24 Gene Ontology (GO) terms of biological process including response to oxidation reduction, hormone stimuli, and biotic and abiotic stimuli. Additionally, three common pathways were identified. These results could not only promote the work on the molecular regulation mechanism under low-P stress in soybean, but also facilitate the cultivation of high-phosphorus-acquisition and high-phosphorus-utilization soybean varieties.
... They found that the phenolic acids used were consistently and significantly inhibitory only at low nutrient concentration, indicating that allelopathy of phenolic compounds is preferentially expressed in low fertility soils. Hall et al (11) observed that the inhibition of chlorogenic acid on pigweed growth was eliminated after the addition of nutrient solution to the soil. However, Blum and Kristofer (19) suggested that the allelopathic activity of phenolic acids might be important in both nutrients limiting and non-limiting soils for some species. ...
Article
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The differential expressions of key enzyme genes involved in Phenylalanine metabolism pathway in allelopathic rice, PI312777 and its counterpart, Lemont under low nitrogen treatment were investigated using real-time fluorescence quantitative PCR(qRT-PCR). The expressions of all nine enzymatic genes involved in phenolic synthesis were increased by 2.3-6.0 folds in the leaves and by 1.9-5.4 folds in the roots of allelopathic rice, PI312777, respectively. Two genes encoding CoA-ligase and salicylate glucosyl transferase, showed 1.7 and 2.3 folds down-regulations in the leaves respectively, when exposed to the lower nitrogen supply. However, in the non-allelopathic rice (Lemont), the expressions of these genes were mostly down-regulated from 1.4 to 3.5 times in the roots and from 1.2 to 4.0 times in the leaves, with the exception of cinnamoyl alcohol dehydrogenases up-regulated by 1.5 folds in the leaves, PAL and Cinnamoyl-CoA up-regulated by 1.0 and 1.4 folds respectively in the roots. HPLC analysis confirmed that allelopathic rice had an increased exudation of phenolic compounds when supplied with lower nitrogen, resulting in an elevanted allelopathic activity, while little change occurred in non-allelopathic rice. Further analysis suggested that the nutrient-stressed condition might induce the synthesis of signal molecules such as SA, then trigger a cascade of systemic chemical defence reactions through up-regulated expressions of relevant genes involved in phenylpropanoid metabolism pathway because of the decreased demand for proteins required for rice growth when exposed to low nitrogen supply. In this process, ammonium ions released by PAL can be assimilated to increase N cycling for compensating nitrogen deficiency. The resulting N-free carbon skeletons of t-cinnamate can be shunted into phenylpropanoid metabolism. This in turn resulted in increased production of phenolic compounds. Thus the increase of phenolic acids enhanced the allelopathic potential in rice, when exposed to lower nitrogen supply, in others words, phenolic acids as allelochemicals played a key role in rice allelopathy, especially in environmental stress.
... It is well known that normal plant growth is controlled by compounds that endogenously produced in the plant (Davies, 1987). But, the production of endogenous plant hormone is not enough for optimum plant growth under environmental conditions (Arteca, 1996;Hall et al., 1983). That is why; plant hormones were exogenously applied to modifying the plant growth by altering the balance of endogenous plant hormone (Nickell, 1982). ...
Article
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In modern agriculture, the role of plant growth regulators is very important. These are the substances which are known to control plant's physiological and biochemical processes at low concentration. These physiological processes include crop development, flowering, regulation of chemical composition of plants and control of mineral uptake from the soil. The plant growth regulators are regarded as a new generation agrochemicals after fertilizers, insecticides, fungicides and herbicides are known to improve source sink relationship and stimulate the rapid translocation of photo assimilates. Plant growth regulators are the chemical substances, when applied at lower concentration improve the growth and yield of crop by stimulating part of natural growth regulatory system.Allelopathy involves both stimulatory and inhibitory biochemical interaction between all types of plants including micoorganisms. The growth promoting effects of allelopathy can be used in various ways such as growing crops having growth promotive potential in rotation and by foliar application of plants water extracts which have promotive effects on other crops. It is a well-known fact that the allelochemicals activity depends upon concentration. The concentration of allelochemicals is inversely related to the promotive effect of plant. At higher concentration, the allelochemicals have inhibitory effect and at low concentration, the allelochemicals have promotive effect. Moreover, the results of these chemicals was not due to a sole chemical, but they work in one or more combinations to show the combined effect to inhibit the germination and growth of weeds.
... Allelopathic potential of sunflower weed control has been reported in wild as well in its cultivars viz., 'Ramsum HS-52', 'Peredovik', 'Hybrids 201,' '8941' (Leather 1983). In greenhouse studies, sunflower 'Russian Mammoth' residues reduce both, seed germination and biomass of weeds (Hall et al. 1983). The aqueous extracts as well as growing plants inhibit seed germination and seedling growth of A. theophrasti, Datura stramonium, Ipomoea spp., and Brassica kaber (Dharamraj et al. 1994a, c). ...
Chapter
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Use of smothering crops as allelopathic strategies could provide weed control, both in summer and winter crops. Although, these crops do not provide complete weed control they can manage weed population at economic threshold levels. This may either eliminate or minimize the use of present herbicides and thus overcome all the major problems associated with herbicides. These studies have shown the potential of weed control of summer and winter crops. Weed suppression in summer crops followed this order: pearl millet > maize > sorghum > cluster bean > cowpea and the order in winter crops was: Egyptian clover > oat > lentil > wheat. Studies with accessions of pearl millet and Brassica spp. (B. juncea, B. napus, B. carinata) exhibited greater variability in their weed smothering ability. Domesticated plants may offer a great scope for selection of weed smothering spp. In the promising crops, their varieties may be screened for smothering potential. The genes responsible for production of smothering allelochemicals may be identified and possibly transferred to develop new transgenic varieties of same or other crops using techniques of biotechnology so that plants could produce their own herbicides.
... Indeed, two areas of future research opportunity include the design of cover crop mixtures to maximize biological nitrogen fixation of legumes and also the design of mixtures that will stimulate accumulation of effective phytotoxic compounds. Plant stress has been shown to increase the production of allelopathic compounds in several plant species (Hall et al., 1983;Williamson et al., 1992), and appropriate interspecific competitive interactions in a cover crop mixture may help to maximize allelopathic mechanisms of weed control. ...
Article
Organic grain cropping systems typically depend on intensive mechanical cultivation for weed control and manure or compost applications to meet plant nutrient demands. However, cover crops may contribute to weed suppression and soil fertility, potentially increasing crop yield and sustainability of the system. The utility of individual cover crop species have been well documented, but the agronomic benefits of diverse cover crop mixtures have received less attention. Cover crop mixtures are an appealing option for farmers, as increasing species diversity has been shown to increase resource-use efficiency, stability, resiliency, and productivity of plant communities. Despite the growing interest in cover crop mixtures, little is known about the effect of increasing cover crop diversity on cropping system performance. Moreover, organic farmers have questions about the most effective method for cover crop mixture termination. In an effort to increase knowledge about cover crop mixtures and management for the western Corn Belt, an organic cropping systems trial was initiated in 2009 at the UNL ARDC near Mead, NE. Spring-sown mixtures of cover crops, ranging from two to eight species, were included in a sunflower – soybean – corn crop rotation. Cover crops were planted in late-March and terminated mechanically with either a field disk or sweep plow undercutter in late-May. Changes in cover crop mixture influenced cover crop productivity and early-season weed biomass, while termination method drove differences in weed community composition, soil microbial community structure, soil moisture and nitrogen, and crop yield. Interestingly, the management of ambient weed communities as a cover crop led to unique shifts in soil microbial community structure, but did not alter soil nitrogen or crop yield when compared to cover crop mixtures. When considering cropping system performance in combination with potential environmental benefits, diverse cover crop mixtures paired with a sweep plow undercutter for termination seems to be a profitable and sustainable management option for organic grain farmers in the western Corn Belt.
... These effects have already been reported for the common sunflower (H. annuus L.), the residues of which can affect germination and growth of several weed species and crops (Bhowmik & Doll, 1982;Hall et al., 1982Hall et al., , 1983Narwal et al., 1999;Azania et al., 2003). ...
Article
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Helianthus tuberosus L. (Jerusalem artichoke) is a perennial herbaceous species which is cultivated for human and animal consumption and sometimes reported as a dangerous weed in several summer crops. Few reports indicate that this species shows allelopathic behaviour. This study, carried out in laboratory and greenhouse conditions, investigated the effects of aqueous extracts from leaf tissues and powdered dried leaves on total seed germination, speed of germination and shoot and radicle elongation of several annual population species. Aqueous extracts were applied at 2.5, 5, 10 and 20%, to seeds in Petri dishes, and powdered dried leaves were applied at 2 t ha to seeds planted in pots. The crops included in the experiments were maize (Zea mays L.), green bean (Phaseolus vulgaris L.), pea (Pisum sativum L.), rice (Oryza sativa L.), tomato (Lycopersicon esculentum Mill.), winter wheat (Triticum aestivum L.), and zucchini (Cucurbita pepo L.). Weed species were Amaranthus retloflexus L., Chenopodium album L., Digitaria sanguinalis (L.) Scop., Echinochloa crus-galli (L.) Beauv., Portulaca oleracea L. and Solanum nigrum L. According to their sensitivity, tested species were grouped into negligibly or poorly sensitive, sensitive to high concentrations and sensitive. Species belonging to the first group were maize, green bean, pea, C. album and P. oleracea. Species sensitive to the highest concentrations were rice, winter wheat, D. sanguinalis and S. nigrum. In the last group, which included tomato, zucchini, A. retroflexus and E. crus-galli, total germination of the last three species was reduced by about 49%, on average. S. nigrum showed no germination at 20% extract concentration. In general, speed of germination was affected more than total germination. In some cases, in particular at low concentrations, a stimulatory effect was recorded.
... 216 Chlorogenic acid added to soil increased N, but reduced P in pigweed (Amaranthus) plants. 217 Some of the inhibitory effects can be overcome by fertilizer application. ...
Article
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Numerous reports have been published on the occurrence, isolation, and characterization of phenolic compounds in plant-soil systems. The low molecular weight phenolics are of great interest because of their effects as allelopathic compounds and plant growth regulators, and they have traditionally been considered as defense molecules in plant-pathogen interactions. More recently, their role as signal molecules in plant-microbe systems has become evident. Specific molecules can act either as inducers for virulent genes in plant-pathogen systems, such as Agrobacterium, or as inducers and “repressors” in Rhizobium-legume and probably other symbiosis. The overall regulation role of these compounds in compatible and incompatible host-microbe interactions is discussed in this review.
... Most of the natural products that cause allelopathy are secondary products, synthesized by plants and microorganisms, and most of the currently identified compounds are products of the shikimic acid and acetate pathways (Rice, 1984). Allelopathy is affected by many factors, e.g., light quality, light intensity, day length, nutrient limitation (N, P, K, B, Ca, Mg and S), soil moisture, temperature, age of plant organs, genotype, other allelochemicals, and plant density (Figure 1; Rice, 1974;Hall, Blum, and Fites, 1983;Einhellig and Eckrich, 1984;Field et al., 1992;Weidenhamer, 1996). These factors make the effects of allelochemicals very complicated. ...
Article
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Rotation systems and allelopathic interactions between plants-plants, plants-insects, plants-microorganisms would be important to exploit allelopathy in optimising the production of rotation systems. The objective of this study is to provide evidences for the importance of allelopathy in crop rotation for weed, insect and disease management with minimal application of external inputs. The relationships between allelochemicals and environmental factors are a key for the growth of plants under rotation. Examples from field crops, forage crops, horticultural species, weeds, and microbes provide evidences for the role allelopathy plays in crop rotation systems. In conclusion, the selection of certain plant sequences under standard environmental conditions may lead to suppression of weeds, insects and diseases and avoid yield decline.
Article
In this study, fourteen active phosphorus solubilizing bacteria (PSB) were obtained by qualitative and quantitative experiments from the rhizosphere of persimmon grown in Beijing, China, with a relatively dry climate. Based on the 16S rRNA gene sequencing, the PSB isolates were clustered under two phyla with Proteobacteria (accounting for 64.28%) and Firmicutes (35.72%). The former included four genera, Pseudomonas (28.57%), Phyllobacterium (21.43%), Variovorax (7.14%), and Mesorhizobium (7.14%), while Bacillus (21.43%) and Paenibacillus (14.29%) belonged to Firmicutes. These PSB strains showed different degrees of phosphate solubilization capacity from 8.36 to 226.28 mg/L in the fermentation culture. Further, the plant growth-promoting potentials include indol-3-acetic acid (IAA), siderophores, and proteases. Among them, eleven PSB strains produced IAA, ten strains had proteolytic activity, and four can produce siderophores. Significantly, this study was the first report of the PSB derived from the rhizosphere of persimmon trees, and the new functions of some isolates were detected as follows, V. soli SHI05 and M. helmanticense SHI08 can simultaneously produce IAA, siderophores, and proteases, P. knackmussii SHI01 and P. sophorae SHI12 can produce IAA, P. frederiksbergensis SHI02, P. illinoisensis SHI09, and P. illinoisensis SHI13 can secrete proteases, P. sophorae SHI03 can produce siderophores. The effect of bacterial inoculation on the early growth of mung bean revealed that V. soil SHI05 can distinctly improve the seed vigor index, total length, fresh weight, dry weight, and root activity of mung bean, increasing by 28.65, 28.71, 174.14, 237.56, and 9.39%, respectively, compared to the positive control (Bacillus megaterium). This showed that the rhizosphere of the persimmon tree was rich in diverse and multifunctional PSB, and V. soli SHI05 may have great potential to become a high-quality candidate microbial fertilizer agent in promoting the growth of mung bean.
Article
Monocropping of sugarcane is highly profitable to the farmers and sugar industry, as it reduces the production cost by 30-40%. But productivity of sugarcane under multiratooning is declining by 30-50% every year due to reduction in cane population per hectare in the state of Maharashtra. The objectives of this study were to explore the changes in beneficial and phytotoxic ratoon cane rhizosphere microflora, soil enzymes and soil NPK level under sugarcane monocropping from high recovery zone and medium recovery zone. The intensive monocropping of sugarcane was found to induce soil sickness due to accumulation of allele chemicals released from sugarcane trash and root exudation, development of phytotoxic microflora and one sided nutrient exhaust. It also caused almost double increase in phytotoxic fungal and bacterial population along with five times more stimulation in the activities of soil enzymes like dehydrogenase, cellulase and amylase. All such alterations correlate with drastic reduction in ratoon cane yield as compared to plant cane.
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Allelopathic effects of a sunflower (Helianthus annus L.) variety, Hysun 38, were studied on two wheat varieties Margalla 99 and Chakwall 97. For this, three experiments were conducted. The first experiment was conducted by growing sunflower in pots to evaluate its effect) on beneficial soil microorganisms (Rhizobium, Azosprillum, and PhosphateSolubilizing Bacteria) and 2) on soil physicochemical properties. The quantification of allelochemicals ( alkaloids, favonoids, and phenols) in leaves, stems and roots of sunflower were made ; more allelochemicals were found in leaves, followed by roots, and the least amount of allelochemicals were found in stem. The Rhizobium, Azosprillum, and phosphate-solubilizing bacterial colonies declined in the soil cultivated with sunflower. Its effects were shown on the carbon nitrogen utilization pattern of the microbes as revealed by the Quick testing system (QTS) while no effect was shown on the gram staining test. The effect of sunflower was also shown on moisture contents of soil, phosphate, etc., the Ca and Mg contents of soil were increase. The second experiment was conducted in petri dishes. The aim was to check allelopathic potential of sunflower on germination rate, fresh weight, dry weight, root length, shoot length, hormonal contents (Indole acetic acid, Gibberellin and Abscisic acid), and chlorophyll, protein, proline, sugar, and DNA contents of wheat seedlings. It was noted that the allelopathic effect was more as the concentrations of extract of sunflower increased as compared with control. The allelochemical effect decreased the values of fresh weight, dry weight, root length, shoot length, GA, IAA, Chlorophyll, protein, proline, sugar, and DNA while increasing the values of ABA. It was also noted that the allelopathic effect of sunflower leaves was greater than the roots, and the least amount of effect was noted in stem. The third experiment was conducted in pots in order to check the effects of sunflower extracts on the comparative growth of wheat and weed. The fresh and dry weight of wheat and weed density at 40 days after sowing (DAS) and at 70 DAS were determined In addition the phytohormone contents, chlorophyll, protein, proline, sugar, DNA contents and yield of wheat were determined. From the pots experiments, it was concluded that sunflower leaves extract had decreased weed fresh weight and dry weight as well as the Gibberrellin and Indole acetic acid contents but increased Abscisic acid contents of wheat seedling.
Article
Allelopathy is a well known area of active research in ecology. However, its importance in agro-ecology is still underappreciated. This review sets out to address this situation and introduce this new and developing field to a wider research audience and to stimulate new research in it. The review starts with an introduction, followed by discussions of allelochemicals, the role of allelopathy in crop production, Allelopathy related problems in crop production, and Suggestions for future research. It also describes broader research into allelopathy in agriculture and the biosciences, and literature resources on the subject. We hope that it will encourage more scientists to initiate research into this exciting new field.
Chapter
This chapter describes the potential relationships, where they may exist, for direct transfer of organic compounds between plants, plant communication and allelopathic interactions. Defines the boundaries for allelopathic interactions, summarizes terminology and outlines standard approaches to the study of allelopathic interactions.
Article
Several crop and weed species were field grown to maturity and their residues incorporated with soil to determine the effects of the plant residues on the growth of subsequent plantings in a spring-fall planting sequence in 1980 to 83. Growth of Palmer amaranth ( Amaranthus palmeri S. Wats. # AMAPA) was studied in 1984 and 1985, and the effects of soil-incorporated Palmer amaranth on the growth of cabbage ( Brassica oleracea var. Capitata L.) and carrot ( Daucus carota L. var. sativa ) seedlings were studied in 1985. Under warm, moist, saline soil conditions and intense sunlight following the spring plantings of the 1980 to 83 study, soil-incorporated residues of Palmer amaranth inhibited the growth of carrot 49% and onion ( Allium cepa L.) 68%. Johnsongrass ( Sorghum halepense L. Pers. # SORHA) residues inhibited the growth of onion 67%, and in one of two years inhibited the growth of cabbage 26% and common sunflower ( Helianthus annuus L. #HELAN) 10%. In 1984 and 1985, Palmer amaranth grown at population densities of 300 plants/m ² attained heights of nearly 2 m and biomass of 2 to 3 kg/m ² within 10 weeks after planting. Phytotoxicity with these biomasses persisted 11 weeks in cabbage and carrot plantings. In 1985, phytotoxicity was dissipated 16 weeks after soil incorporation of the weed.
Chapter
This chapter describes in some detail a number of standard (common or classical) laboratory screening bioassays for identifying putative allelopathic plants and sensitive species. These include bioassays for the following: identified putative allelopathic compounds, leachates, “root exudates plus”, litter and residues, and soils. The procedures of each bioassay have been adjusted, where possible, to be consistent with the tenets of Chap. 3. Comments regarding potential benefits and limitations of these bioassays are also provided throughout the chapter.
Chapter
This chapter describes a number of standard seed and seedling laboratory bioassays for identifying and characterizing the effects and causes by which identified putative allelopathic compounds, mixtures of allelopathic compounds, mixtures of organic and/or inorganic compounds, and residues may stimulate or inhibit sensitive weed species. Five different approaches will be described: (a) a bioassay for simple mixtures of identified putative allelopathic compounds, (b) a bioassay for residue leachates plus or minus XAD-4 resin, (c) the application of regression analysis to data from residue and soil extract bioassays, (d) a bioassay for determining the role of treatment surface area, and (e) using omics methods as tools to determine modes of action.
Chapter
This chapter describes and provides comments on the following basic features of laboratory bioassays: (a) biotic and physicochemical factors, (b) test materials, (c) measurements, hypotheses, experimental designs, and data analyses, and (d) basic information that should be provided by researchers for all bioassays.
Chapter
This chapter describes the underlying criteria and assumptions in the development and execution of bioassays utilizing model systems in the laboratory. It provides details and commentary regarding the materials and methods used. Describes and discusses the results and significance of the following: (a) effects and duration of effects for individual phenolic acids, mixtures of phenolic acids, and phenolic acids in combination with other organic and inorganic compounds on seedlings growing in nutrient and in soil cultures, (b) the interactions of phenolic acids with seedling roots, bulk-soil and rhizosphere microbes, and soil particles, (c) the relationships between phenolic acid-utilizing microbes, soil characteristics, and seedling inhibition, (d) the effects of phenolic acids on the various life stages of plants, (e) what happens to phenolic acid concentrations over time in nutrient culture and seedling-microbe-soil systems, and (f) the relevance of laboratory bioassays to field studies.
Chapter
This chapter provides a general introduction to this volume, discusses the nature of plant-plant allelopathic interactions, describes the nature and sources of allelopathic compounds in soils, discusses the concepts of holism and reductionism as they relate to laboratory bioassays, provides a listing of benefits, limits, and common pit falls (e.g., false assumptions and misconceptions) for laboratory bioassays, and answers or sets the stage for answering the following questions: (a) Why is it important to design laboratory bioassays that are more holistic or stated in a more pragmatic way more relevant to field environments? (b) What can be done to make laboratory bioassays more relevant to field environments? and (c) Is it always necessary to make laboratory bioassays relevant to field environments?
Chapter
This chapter discusses a number of issues and challenges associated with creating more relevant model laboratory bioassays including the following: treatment concentrations, mobility and transport, species density, symbiotic relationships, microorganisms, controls and references, and measurements among others.
Chapter
This chapter describes the underlying criteria and assumption in the development and execution of field and associated laboratory bioassays. It provides details and commentary regarding the materials and methods used. More specifically, describes how glyphosate-desiccated wheat and other cover crops (crimson clover, subterranean clover, and rye) in no-till systems can directly and indirectly influence morningglory, pigweed, and prickly sida seedling emergence, with emphasis on the role of phenolic acids in plant residues and soil.
Article
The leaf leachates (20, 40, 60, 80 g L-1) of Zanthdxylum bungeanum affected the soil enzymatic properties and growth of its own seedlings. Leaf leachates at concentrations of 60, 80 g L-1, significantly inhibited the seedlings root biomass. With the increase in leaf leachate concentrations, soil polyphenoloxidase activities increased greatly but soil catalase, protease and acid phosphatase were decreased significantly. The lower concentration (20 g L-1) of leaf leachates had no effect on ascorbate peroxidase (APX), Superoxide dismutase (SOD) and catalase (CAT) of seedlings but higher concentrations were inhibitory. Likewise, the malondialdehyde (MDA) contents in seedling leaves decreased significantly at 20 g L-1 and increased at higher concentrations (over 60 g L -1). Soil available nitrogen was greatly enhanced at the 20 g L -1 concentration, but declined at higher concentrations. However, soil available phosphorus decreased in all concentrations. Some significant relationships were observed among the soil chemical properties, enzymatic activities and the seedling physiological indices with leaf leachates.
Article
The effects of caffeic, vanillic, p -coumaric, chlorogenic, and ferulic acids, ragweed parthenium ( Parthenium hysterophorus L. # PTNHY) residue and extracts on the growth, ion uptake, and chlorophyll content of 3-week-old tomatoes ( Lycopersicon esculentum Mill. ‘Walter’) grown in the greenhouse were determined Vanillic, p -coumaric, chlorogenic, and ferulic acid at 10 ⁻³ M and parthenium extract at 0.5% (w/v) significantly reduced tomato root and shoot dry weight. Ragweed parthenium residue at 0.5% (w/w) and extract at 0.5% (w/v) significantly reduced tomato shoot and root dry weight. Leaf nitrogen content was reduced by phenolic acids (10 ⁻³ M) and ragweed parthenium extract (0.5%). Phosphorus content was reduced by all phenolic acids at 10 ⁻³ M and ragweed parthenium extract at 0.5% (w/v). In addition, p -coumaric and ferulic acids at 10 ⁻⁴ M reduced phosphorus content. No consistent relationship between chlorophyll content and tomato growth reduction was observed.
Article
A two-factorial field trial with winter faba bean was carried out at the experimental farm for Organic Agriculture 'Wiesengut' close to Bonn, Germany, in 2007 and 2008 respectively. The objective of the experiments was to quantify and evaluate the influence of the factors variety (Hiverna and Diva) and cover crop species (sunflower, buckwheat, green fallow) on a range of growth, yield and weed parameters of organically grown winter faba bean. Data were subjected to ANOVA with subsequent Tukey- Test. Crop height of winter faba bean was significantly lower after cover crop sunflower compared with buckwheat. In a joint two-year analysis grain yield of winter faba bean after cover crop sunflower was significantly lower (3.09 t DM ha -1) compared with buckwheat (3.48 t DM ha-1). Weed ground cover and biomass were significantly lower after cover crop sunflower and buckwheat compared with green fallow at several assessment dates of both trials. Results have shown that under the climatic conditions of the Rhineland area the production of organic winter faba bean can be realized with economic yields. The practical use of cover crops such as sunflower known to feature allelo pathic effects against weeds still deserves further research.
Article
Field and controlled environment studies were conducted to examine the effects of plant stress during growth on the subsequent phytotoxicity of residues of Brassica napus and Brassica campestris. High temperatures (30°C compared to 15°C day temperature) and short days (8 hours light compared to 16 hours light) increased the phytotoxicity of residues as measured by a wheat bioassay. Low levels of nutrient supply during growth also increased the toxicity of Brassica residues. The effect of water stress was less clear; severe moisture stress resulted in less phytotoxicity than mild water stress. The two species showed some differences in wheat phytotoxicity following applied plant stress and the field experiments suggested there was a potential for greater toxicity from summer grown residues.
Book
Provides an in-depth analysis of phenolic acids in laboratory seedling-microbe-soil model systems Offers a blue print for plant-plant allelopathic interactions Extensively lists if-then hypotheses for plant-plant allelopathic interactions Discusses past, present, and future paradigms for studying plant-plant allelopathic interactions Updates criteria for identifying plant-plant allelopathic interactions in nature In an effort to implement conservation measures farmers have used a variety of production methods including reduced or zero tillage. With the implementation of these methods there has been an increase in the use of small grain and legume cover crops and their residues. One benefit of these production methods has been early season weed control. Presently the most promising cover crops and their residues for annual broadleaf weed control in temperate regions of the world are the small grains such as wheat and rye. The literature suggests that a variety of mechanisms are involved in regulating weed seedling emergence, among them the allelopathic effects of phenolic acids. This book addresses the following questions: How likely are the necessary phenolic acid concentrations and environmental conditions present in wheat no-till cropping systems for inhibition of annual broadleaf weed seedling emergence? and Do phenolic acids have a dominant role in regulating annual broadleaf weed seedling emergence or are phenolic acids just one component of a larger promoter/modifier/inhibitor complex in wheat no-till cropping systems? The book has four chapters covering: 1. allelopathic plant-plant interactions, 2. laboratory experiments, 3. field and associated laboratory experiments, and 4. conclusions and suggested future research. There are several things that are unique about this book: a. The format is that of a research paper published in scientific journals. b. It differs from the journal format in that logic, reasons, and justifications for various procedures are provided. c. The Scientific Method and its approach to research are emphasized. For example, if-then hypotheses and cons and pros are provided so that readers can draw their own conclusions. and d. Although a broad range of literature is included, this book is a retrospective analysis of some 20 plus years of research on plant-plant allelopathic interactions at North Carolina State University. © Springer Science+Business Media B.V. 2011. All rights reserved.
Article
Predicting crop yield reductions from weeds continues to challenge weed science. Useful methods based upon weed densities and upon area weeds influence have been developed. Results vary greatly from year to year and location to location for several reasons which are reviewed: 1) the shift in crop yield from a weed density-dependent to a weed density-independent relationship; 2) the effect of density on essential growth factor competed for; 3) differences among weed species in relative competitiveness for essential growth factors; 4) the differential effect of environmental conditions on the competitiveness of weed species; and 5) the effect of time of emergence on competition. To reduce the variability in prediction methods will necessitate developing a method based upon the factor(s) responsible for yield reduction.
Article
Cotton and pitted morningglory emergence and dry weight decreased approximately 60 to 80% when these plants were grown under greenhouse conditions in the presence of increasing amounts (0.8 to 6.7 mg debris/g soil) of field-grown crimson clover or hairy vetch debris incorporated into the soil medium. Conversely, corn dry weight increased 20 to 75% when legume debris was placed on the soil surface; incorporated debris had very little effect on corn emergence or dry weight. Germination and seedling growth of corn, Italian ryegrass, cotton, pitted morningglory, and wild mustard decreased progressively, with species-dependent variation, when exposed to increasing concentrations (8.3 to 33.3 g debris/L) of aqueous crimson clover and hairy vetch extract. Mustard and ryegrass germination and growth were almost completely inhibited by full-strength extracts of both legumes. Bioassay species exhibited greater phytotoxic responses to hairy vetch than to crimson clover in the debris and extract studies. Emergence and growth of corn and cotton were not affected when planted into soil samples, containing root biomass and possible leaf and root exudates, collected from beneath field-grown hairy vetch and crimson clover plants. However, morningglory dry weight increased 35% in the presence of either legume root debris and accompanying soil.
Article
The accepted criteria for identifying allelopathic interactions in the field that have been proposed in the literature offer heuristic function, but to date have failed as a framework for research and diagnostics. If the present criteria are to be modified to make them useful empirically, their shortcomings must be identified. For this review, data from the literature and from defined model systems consisting of plants, soil, and/or microbes are used to evaluate the applicability of the accepted criteria to defined systems in which plants are responding to known allelochemicals. Based on this evaluation, modified criteria are proposed. In many respects, however, the modified criteria are as difficult to satisfy in the field as those proposed previously. The new criteria have value as a research framework because they clearly suggest that a shift in research focus to the soil environment, specifically the barrier of the rhizosphere through which allelochemicals must pass, is essential if the role of allelopathic interactions in the field is to be established.
Article
Cucumber seeds and seedlings at various ages (7-19 days old) were treated with a single treatment or multiple treatments (at 2-day intervals) of ferulic acid in nutrient culture. Ferulic acid treatments of cucumber seeds during stages of germination and radicle growth did not significantly reduce subsequent seedling growth. Ferulic acid treatments to seedlings reduced leaf area, leaf expansion, and dry weight of cucumber seedlings. Pretreatment of seeds and seedlings with 0.1 or 0.2 mM ferulic acid did not modify the effects of a single 1 mM ferulic acid treatment on leaf expansion when a single treatment was given at various times to seedlings ranging from 7 to 19 days of age. Treatments of 1mM or greater induced rapid wilting of leaves, but visible recovery occurred within 24-48 hr and subsequent treatments did not cause wilting. Once seedlings were removed from ferulic acid treatments, leaf expansion resumed. The magnitude of recovery depended on the concentration of ferulic acid, frequency of ferulic acid application and age of the seedling. Mean relative rates of leaf expansion recovered rapidly even in the presence of ferulic acid. Recovery of leaf expansion after ferulic acid treatments was faster for seedlings grown in an adequate nutrient environment than for seedlings grown in a limited nutrient environment. Ferulic acid disappeared from nutrient solutions with time, and two microbial metabolic products of ferulic acid (i.e., vanillic and protocatechuic acid) were identified in nutrient solutions.
Article
It has been suggested that the allelopathic activity of phenolic acids should be primarily important in soils of low fertility. If this is true, then plant growth inhibition by phenolic acids may be unimportant in managed agricultural soils. The objective of this study was to determine how soil nitrogen (N) level might modify phenolic acid inhibition of growth. Cucumber seedlings (Cucumis sativus cv Early Green Cluster) grown in containers in growth chambers under varying N levels (5, 10, 15, 20, and 25 μg N/g soil) in Portsmouth B,-horizon soil material were treated with ferulic acid (0 or 10 μg/g soil). Nitrogen and ferulic acid (FA) were applied every other day to the soil surface. The amount of FA in the soil solution declined with depth in the containers. A more rapid disappearance of FA from the soil solution was observed for the last FA treatment (0% recovered after 10 hr on day 23) than the first treatment (44% recovered after 10 hr on day 13). Both low N (5 μg N/g soil) and FA treatments reduced shoot dry weight, the mean absolute (AGR) and the mean relative (RGR) rates of leaf expansion, and increased the root-shoot ratio. High N treatments reduced shoot dry weight and the AGR. Ferulic acid inhibited cucumber seedling growth over a range of N concentrations, suggesting that the allelopathic activity of phenolic acids may be important in both nutrient limiting and nonlimiting soils for some species.
Article
Chromatographic procedures were used to isolate inhibitors of seed germination from sweet potato root periderm tissue. The inhibitory activity of all fractions was monitored using a proso millet seed germination bioassay. A single HPLC peak, representing approximately 1.2% of the periderm dry weight, accounted for most of the inhibitory activity. The active fraction was labile in methanolic solution. Further fractionation of this peak by HPLC methods was not successful. In vitro seed germination dose-response relationships were established for the peak. The various seed species exhibited an extremely wide range of sensitivity. The I50 values were 0.16, 0.013 and 0.011 mg/ml for redroot pigweed, velvetleaf, and proso millet, respectively. Tall morning glory was not inhibited by any concentration tested.
Article
Studies of allelopathy have emphasized primarily the identification and quantification of phytotoxins in soils, with only limited attention directed toward how organic (carbon) and inorganic constituents (nutrients) in the soil may modify the action of such phytotoxins. In the present study, increasing carbon (C) levels (up to 108μg C/g soil) supplied as glucose, phenylalanine, orp-hydroxybenzoic acid did not alter morning-glory biomass, but similar C levels supplied as leucine, methionine, orp-coumaric acid were inversely related to morning-glory biomass. Similar joint action and multiplicative analyses were used to describe morning-glory biomass response to various C sources and to generate dose isolines for combinations ofp-coumaric acid and methionine at two NO3-N levels and for combinations ofp-coumaric acid and glucose at one NO3-N level. Methionine, glucose, and NO3-N treatments influenced the inhibitory action ofp-coumaric acid on biomass production of morning-glory seedlings. For example, results from the multiplicative analysis indicated that a 10% inhibition of morning-glory biomass required 7.5μgp-coumaric acid/g soil, while the presence of 3.68μg methionine/g soil thep-coumaric acid concentration required for 10% inhibition was only 3.75μg/ g soil. Similar response trends were obtained forp-coumaric acid and glucose. The higher NO3-N (14 vs. 3.5μg/g) treatments lowered the methionine and increased thep-coumaric acid concentrations required for 10% inhibition of morning-glory biomass. These results suggested that allelopathic interactions in soil environments can be a function of interacting neutral substances (e.g., glucose), promoters (e.g., NO3-N), and/or inhibitors (e.g., methionine andp-coumaric acid) of plant growth.
Article
Experiments were conducted to determine how plant responses to mixtures of allelochemicals may change as the proportion of roots in contact with allelochemicals is modified. Thirteen-day-old cucumber seedlings were treated with ferulic and/orp-coumaric acid in a split-root nutrient culture system. Leaf areas were determined just prior to treatment and at harvest, 24 hr after treatment. Ferulic acid was more inhibitory to cucumber leaf expansion thanp-coumaric acid. The effects of ferulic andp-coumaric acids on leaf expansion were additive. For individual acids, mixtures of ferulic andp-coumaric acids in the same container and combinations of ferulic andp-coumaric acids in separate containers, the inhibition of leaf expansion was directly related to the product of the concentration of the acid(s) and the proportion of roots treated with the acid(s). Pretreatment with 0.2 or 0.4 mM ferulic acid and subsequent treatment with 0.5 mM ferulic acid failed to show evidence of acclimation by cucumber seedlings.
Article
Allelopathy, originally defined as chemically elicited interactions between plants or fungi, is mediated by many types of compounds with different sites and modes of biochemical action. Although it is possible to measure a generalized effect, it is unlikely that deeper insight into the basic mechanisms of this phenomenon will be obtained until problems are more clearly and specifically delineated. Future work should include identification of the compounds found in specific interactions and their evaluation in bioassay systems that use organisms actually involved in the response. A broader range of compounds and test organisms must be considered, and the biochemical sites and mechanisms of interaction must be evaluated, even for compounds that appear to be inactive. Once active compounds have been identified, their release, movement, uptake, and effects on source and target species in the allelopathic system should be examined. The effects of plant density require additional investigation. Studies in which plants are grown in various combinations and ratios can ultimately provide information about the major sources of allelopathic interaction in communities, the role of allelopathy in succession, and the nature and extent of coadaptation of organisms. Understanding the role of allelopathy in succession will require information about the chemistry and biology of interactions, and a better understanding of the ecological factors involved. Agricultural systems can supply much needed information, as they are similar to natural systems but usually are simpler and better defined. In turn, a better understanding of allelopathy is important in many phases of modern agriculture, especially in the tropics. By attacking allelopathic interactions at several organizational levels, the effects collectively known as allelopathy can be understood, even in complex natural communities. Major advancement in understanding allelopathy will be accomplished only by the combined effort of investigators from many disciplines.
Article
This article summarizes allelochemicals' active variety, its potential causes and function mechanisms. Allelochemicals' activity varies with temperature, photoperiod, water and soils during natural processes, with its initial concentration, compound structure and mixed degree during functional processes, with plant accessions, tissues and maturity within-species, and with research techniques and operation processes. The prospective developmental aspects of allelopathy studies in the future are discussed. Future research should focus on: (1) to identify and purify allelochemicals more effectively, especially for agriculture, (2) the functions of allelopathy at the molecular structure level, (3) using allelopathy to explain plant species interactions, (4) allelopathy as a driving force of succession, and (5) the significance of allelopathy in the evolutionary processes.
Article
The effects of leaves and litter of the boreal forest understory shrub, Ledum groenlandicum, on soil characteristics and black spruce (Picea mariana) seedling growth were investigated. Organic and mineral soils, not previously associated with L. groenlandicum, were amended with leaves and litter of this species. The objectives of the present study were: (i) to determine the changes in soil characteristics after amending with L. groenlandicum, (ii) to determine the quantitative variation in the concentration of water-soluble phenolic allelochemicals in mineral and organic soil layers modified by L. groenlandicum and (iii) to study the growth response of black spruce in soils treated with different L. groenlandicum amendments. The amended organic and mineral soils were analyzed for pH, organic matter, PO4, N, Ba, Cu, Zn, Fe, Mn, Ca, Na, K, Mg, Al and total phenolics equivalence. Results indicate that organic soils amended with L. groenlandicum leaves and litter were significantly different from unamended control soil for most of the chemical characteristics, while amended mineral soil was different from that of unmodified mineral soil for PO4, organic matter, K and total phenolics equivalence. Water-soluble phenolics from L. groenlandicum and changes in nutrient availability are plausible causes of L. groenlandicum interference with black spruce seedling growth.
Article
Experiments were conducted to determine the potential for acclimation (i.e., increased tolerance) to allelopathic phenolic acids resulting from pretreatment of seedlings with allelochemical (ferulic acid), drought, or nutrient stress. Cucumber seedlings were exposed to pretreatment stresses in a nutrient culture system for nine days, starting with day 3. Seedlings were subsequently treated for 5 hr with 0, 0.25, 0.5, or 0.75 mM ferulic acid. Acclimation (tolerance) was quantified by percentage inhibition of net phosphorus uptake. Seedlings grown with ferulic acid or drought pretreatment stresses were more tolerant to subsequent ferulic acid treatments (i.e., inhibition of net phosphorus uptake by ferulic acid was reduced). Nutrient pretreatment stress eliminated the inhibitory activity of ferulic acid on net phosphorus uptake. The results suggest that a general acclimation response to a variety of pretreatment stresses can confer an increased tolerance of plants to allelopathic phenolic acids such as ferulic acid.
Article
Increased atmospheric CO2 can affect plant growth, so competition among plants may be influenced. Allelopathy is one mechanism involved in plant competition. Experiments were conducted in a controlled-environment chamber to determine if the concentration of atmospheric CO2 altered the dose-response relationship between an allelopathic phenolic acid and tomato seedling biomass. Seeds of Lycopersicon lycopersicum were planted in quartz sand in styrofoam cups and allowed to germinate and grow for 15–17 days. During the next 14 days, seedlings were watered twice daily with nutrient solution amended with p-coumaric acid (4-hydroxycinnamic acid, HOC6H4CH = CHCO2H; ranging 0–0.85 mg mL-1; 5 concentrations in each experiment) and exposed 24 hr day-1 in continuous-stirred tank reactors (CSTRs) to ambient air (335–375 ppm CO2) or ambient air to which 350 ppm CO2 was added (i.e., approximately twice-ambient CO2; two CSTRs per CO2 concentration in each experiment). Dose-response data relating p-coumaric acid concentration and shoot, root, and total biomass were fit to a flexible decay function. In all three experiments, twice-ambient CO2 significantly increased the y-intercept for the dose-response model for the p-coumaric acid effect on shoot biomass by 25–50% but had negligible effects on other aspects of the models. Results suggest that if CO2 affects plant competition, mechanisms involving allelopathic phenolic acids may not be involved.
Article
Reversible sorption of phenolic acids by soils may provide some protection to phenolic acids from microbial degradation. In the absence of microbes, reversible sorption 35 days after addition of 0.5–3 mol/g of ferulic acid or p-coumaric acid was 8–14% in Cecil Ap horizon and 31–38% in Cecil Bt, horizon soil materials. The reversibly sorbed/solution ratios (r/s) for ferulic acid or p-coumaric acid ranged from 0.12 to 0.25 in Ap and 0.65 to 0.85 in Bt horizon soil materials. When microbes were introduced, the r/s ratio for both the Ap and Bt horizon soil materials increased over time up to 5 and 2, respectively, thereby indicating a more rapid utilization of solution phenolic acids over reversibly sorbed phenolic acids. The increase in r/s ratio and the overall microbial utilization of ferulic acid and/or p-coumaric acid were much more rapid in Ap than in Bt horizon soil materials. Reversible sorption, however, provided protection of phenolic acids from microbial utilization for only very short periods of time. Differential soil fixation, microbial production of benzoic acids (e.g., vanillic acid and p-hydroxybenzoic acid) from cinnamic acids (e.g., ferulic acid and p-coumaric acid, respectively), and the subsequent differential utilization of cinnamic and benzoic acids by soil microbes indicated that these processes can substantially influence the magnitude and duration of the phytoxicity of individual phenolic acids.
Article
Wheat (Triticum aestivum L.) and sunflower (Helianthus annuus L.) offer oppurtunities for double-cropping but little is known about possible effects of sunflower residues on wheat in a cropping sequence. In this study, we have investigated effects of sunflower extracts and residues on wheat germination, growth and yield. Wheat germination in a soilless medium was not affected by aqueous extracts of sunflower residues; however, stem and leaf extracts (1:10 dilution) of dried sunflower tissues did inhibit dry-weight gain of 5-day-old wheat seedlings by 20–40%.In greenhouse studies, ground leaves or forage-chopped shoots, when surface-applied, promoted wheat growth. Wheat tissue had significantly greater N in wheat grown with ground leaf residues. Forty-day-old wheat grown in pots with incorporated, chopped sunflower residues had only one-third the dry weight of plants with the same amount of residue on the soil surface. Chopped sunflower residues equivalent to 6.9 Mg/ha suppressed weed numbers by 50% if incorporated, and ground leaf material surface-applied at 15 Mg/ha reduced weed populations by approximately 75% when compared to residue-free treatments.In a split-plot study, wheat was grown following sunflower or fallow. The plot splits were managed as either no-till (residues on surface) or conventionally tilled (residues incorporated). Wheat grain yields were higher in the no-till treatments (5.2 Mg/ha) than in the conventionally tilled treatments (4.9 Mg/ha). Residue applications rates did not affect grain yields. Overall, the results suggest that sunflower residues can inhibit early wheat and weed growth and that incorporation of residues may reduce grain yields, but no-till production of wheat following sunflower appears viable.
Article
Helianthus annuus L. variety “Russian Mammoth” was grown in pots, in both the greenhouse and the field, under density treatments of 1, 3, 6 or 12 plants per pot and nutrient treatments of full‐strength, ½, ¼, ⅛ or 1/16 strength Hoagland's solution. The plants responded in typical fashion to both nutrient and density stress. Within each nutrient treatment, as the density of planting increased, biomass per pot first increased and then leveled off while biomass per plant decreased. Within each density treatment, as the nutrient level decreased, biomass per pot and per plant decreased. Therefore, both nutrient and density treatments imposed a stress (measured as a reduction in biomass) on individual H. annuus plants. Total phenolic compounds from the Helianthus annuus tissue, expressed as chlorogenic acid equivalents and determined by the PVP method, increased with increasing nutrient stress (i.e., lower nutrient availability); however, increasing density stress failed to significantly modify total phenolic compounds. The maximum total phenolic level determined for field‐grown plants (69.70 mg g ‐1 tissue) was approximately 58% greater than that found for greenhouse‐grown plants (44.16 mg g ‐1 tissue). When coarsely ground H. annuus plant material from the stress studies was added to soil, there was a significant depressive effect on germination of Amaranthus retroflexus seeds. In these germination was more closely correlated with total phenolic compounds (chlorogenic acid equivalents) added to the soil by the debris than with any other variable measured. Correlations were best for phenolic values of 200 μg g ‐1 soil or greater. Chlorogenic acid (an abundant phenolic acid present in H. annuus ) did not inhibit A. retroflexus seed germination when added to soil in pure form. The addition of a nutrient solution to soil containing H. annuus debris reduced subsequent inhibition of A. retroflexus seed germination.
Article
The first stage of succession in abandoned fields in central Oklahoma and southeastern Kansas is the weed stage in which Helianthus annuus is an important dominant. The causative factors involved in the short duration of this stage, 2 to 3 years, and its passage into the annual grass stage consisting of one dominant, Aristida oligantha, have long been sought. The present study was undertaken to ascertain the allelopathic effects of Helianthus annuus on species with which it is associated in abandoned fields. Field studies indicated that certain associated species exhibit reduced growth around the sunflower plants, and preliminary experiments indicated that the reduced growth was not due to competition. Extracts of various organs of sunflower plants, decaying leaves, root exudate, leaf leachate, and soils collected from around sunflowers inhibited the seed germination and seedling growth of Helianthus annuus and many associated species, with the exception of Aristida oligantha and Croton glandulosus. Strong correlations were evident between the species with reduced growth in the field and those inhibited through various laboratory tests. Chlorogenic acid and isochlorogenic acid, present in all extracts of the various sunflower organs, and a suspected α-naphthol derivative and scopolin from the leaf leachate were the major phytotoxins identified from the sunflower plants. The phytotoxins of the extracts, leaf leachate, root exudate, and soil extracts are not the same compounds and this indicates that there is probably an additive effect with each group of toxins, thus accentuating the allelopathic effects of sunflower. The present results which indicate that Helianthus annuus is allelopathic to many of the early weeds including its own seedlings, but not to Aristida oligantha, complements the findings of others and may help in explaining the short duration of the weed stage and its replacement by Aristida oligantha in old-field succession of this region.
Article
Steam distillation methods of determining ammonium, nitrate, and nitrite in the presence of alkali-labile organic nitrogen compounds are described. They involve the use of magnesium oxide for distillation of ammonium, ball-milled Devarda alloy for reduction of nitrate and nitrite to ammonium, and sulfamic acid for destruction of nitrite. The methods are rapid, accurate, and precise, and they permit nitrogen isotope-ratio analysis of ammonium, nitrate, and nitrite in tracer studies using 15N-enriched compounds. They give quantitative recovery of ammonium, nitrate and nitrite added to soil and plant extracts, and appear suitable for analysis of biological materials.
Article
The influence of 15 hydroxy-benzoic acids upon active inorganic phosphate absorption by barley roots was examined. For each compound an inhibition constant (ki) was determined, i.e. the concentration of compound required to bring about a 50% inhibition of absorption. The ki values of the benzoic acids were strongly correlated with their octanol—water partition coefficients and their pKa values. This suggests that the inhibition of normal membrane functions, brought about by benzoic acids, results from a generalized increase in cell membrane permeability. Salicylate derivatives were generally more inhibitory than would be predicted from their partition coefficients; their pronounced toxicity probably arises from structural impediments to their detoxication.
Article
A simple modification of the curcumin spectrophotometric determination of boron has been developed in which the acid requiredo develop the colour is destroyed with ammonium acetate, thus eliminating the need for dilution to large volumes. Provided suitable precautions are taken to minimise contamination, the method is suitable for direct determinations of boron down to 0·1 mg of boron per litre.
A User's Guide to Statistical Analysis System (SAS) Steam distillation methods for determination of ammonium, nitrate and nitrite
  • A J Barr
  • J H Goodnight
  • J P Sali
  • J T Helwig
  • J M Bremner
  • D R Kenney
BARR, A.J., GOODNIGHT, J.H., SALI, J.P., and HELWIG, J.T. 1976. A User's Guide to Statistical Analysis System (SAS). SAS Institute, Inc., Raleigh, North Carolina. BREMNER, J.M., and KENNEY, D.R. 1964. Steam distillation methods for determination of ammonium, nitrate and nitrite. Anal. Chim. Acta 32:485-495.
Population Biology of Plants The water-culture method of growing plants without soil The influence of nitrogen and phosphorus levels on the phytotoxicity of phenolic compounds
  • J L Harper
  • D R Hoagland
  • D I Arnon
  • E L Rice
  • L G Stowe
  • A Osbory
HARPER, J.L. 1977. Population Biology of Plants. Academic Press, New York. HOAGLAND, D.R., and ARNON, D.I. 1938. The water-culture method of growing plants without soil. Calif. Agric. Exp. Stn., Circ. 347. RICE, E.L. 1974. Allelopathy. Academic Press, New York. STOWE, L.G., and OSBORY, A. 1980. The influence of nitrogen and phosphorus levels on the phytotoxicity of phenolic compounds. Can. J. Bot. 58:1149-1153.
A User's Guide to Statistical Analysis System (SAS)
  • A J Bark
  • J H Goodnight
  • J P Sali
  • J T Andhelwig
  • A.J. Bark
Estimation of total tobacco plant phenols by their bonding to polyvinylpyrrolidone
  • R A Andersen
Estimation of total tobacco plant phenols by their bonding to polyvinylpyrrolidone
  • R A Andersen
  • J R Andtodd
  • R.A. Andersen
Steam distillation methods for determination of ammonium, nitrate and nitrite
  • J M Bremner
  • D R Andkennet
  • J.M. Bremner
The influence of nitrogen and phosphorus levels on the phytotoxicity of phenolic compounds
  • L G Stowe
  • A Andosborn
  • L.G. Stowe
The water-culture method of growing plants without soil
  • D R Hoagland
  • D I Andarnon