Allelopathic potential and an allelopathic substance in mango leaves

The present study was aimed to determine the allelopathic potential of mango (Mangifera indica L.) leaves and to identify allelopathic substances in the leaves. The aqueous methanol extracts of mango leaves inhibited seedling growth of garden cress, radish, rapeseed, foxtail fescue and crabgrass, and the inhibitory effects increased with the increasing extract concentration, suggesting that mango leaves may contain allelopathic substances. The extract was then purified by several chromatographic runs through a bioassay-directed fractionation, and an growth inhibitory substance was isolated and identified by spectral data as methyl-3,4,5-trihydroxybenzoate (methyl gallate). Methyl gallate at the concentration of 10 mM inhibited 98.6% and 99.8% of root and shoot growth of garden cress relative to the control, respectively, and 94.4% and 49.3% of those of foxtail fescue, respectively. The concentrations of methyl gallate required for 50% growth inhibition (I₅₀) on garden cress roots and shoots were 3.9 and 3.3 mM, and those on foxtail fescue roots and shoots were 1.5 and 9.5 mM, respectively. It is the first report of an allelopathic substance in mango leaves and allelopathic activity of methyl gallate. Therefore, the mango leaves may have potential as a soil additive material for the weed management options.     

Two allelopathic substances from Paspalum commersonii Lam.

Paspalum commersonii (Poaceae) is a herbaceous perennial weed distributed in the tropics and subtropics regions and grows mainly in the moist, or even flooded soil. It often appears in the rice field as a competitive weed and difficult to manage. Its strong competitive nature indicates possible allelopathic potential of P. commersonii. However, no studies have been found yet on the allelopathic activity of P. commersonii. Thus, we investigated the allelopathic potential of this weed and determined its allelopathic substances. Aqueous methanol extracts of P. commersonii showed concentration-dependent inhibitory activity on the seedling growth of cress, alfalfa, rapeseed, lettuce, barnyard grass, foxtail fescue, Italian ryegrass, and timothy. Two substances were isolated through bioassay-guided fractionation and their structures were determined through spectral data as dehydrovomifoliol and loliolide. Dehydrovomifoliol and loliolide started inhibiting the shoot and root growth of cress at concentrations greater than 3 and 0.03?mM, respectively. The concentrations required for 50% inhibition (I₅₀) of cress shoot and root growth were 3.34 and >3.50?mM for dehydrovomifoliol and 0.04 and 0.05?mM for loliolide, respectively. These results indicate that both substances may affect the inhibitory activity of P. commersonii.     

Promotion of phytotoxic bacteria in rhizospheres of leatherleaf fern by benlate DF

Foliar damage symptoms to leatherleaf fern (Rumohra adiantiformis [Forst] Ching) in Florida during widespread use of the fungicide Benlate DF could not be attributed to nutrition, cultural practices, environmental conditions, or new pathogens developing on the crop. The objective of this study was to assess the involvement of rhizosphere bacteria in the damage symptoms using bioassays to detect phytotoxic activity. Rhizosphere bacteria were cultured from rhizospheres of leatherleaf ferns sampled from ferneries where Benlate DF was routinely applied and from check ferneries not receiving the fungicide. Using a lettuce seedling bioassay, the proportion of rhizosphere bacteria that was plant growth‐inhibitory ranged from 7.5% and 11% for isolates from two check ferneries to 70% for those from a fernery previously treated with Benlate DF. Rhizosphere bacteria originating from Benlate DF‐treated leatherleaf ferns caused most severe damage on seedlings with some isolates reducing root growth 70% compared to control seedlings. Other symptoms induced by these bacteria, which were mainly fluorescent and nonfluorescent pseudomonads, included necroses and inhibition of root hair development. Results suggested that Benlate DF affected the composition of bacteria in leatherleaf fern rhizospheres by promoting a bacterial component with phytotoxic properties toward plant growth.     

Isolation of phytotoxic compounds from tree-of-heaven (Ailanthus altissima swingle)

The aqueous root extract of Ailanthus altissima showed allelopathic activity against radish (Raphanus sativus L. cv. "Saxa"), garden cress (Lepidium sativum L.), and purslane (Portulaca oleracea L.) seeds. A bioassay-oriented purification of active extracts, chromatographic fractions, and compounds demonstrated dose-dependent activity on germination and radicle growth of test seeds; radish seed was the most sensitive to allelochemicals. Active compounds have been isolated: ailanthone, ailanthinone, chaparrine, and ailanthinol B (quassinoid derivatives); the alkaloid 1-methoxycanthin-6-one is not active. The compound with greatest inhibitory activity is ailanthone. The data obtained suggest a possible use of tree-of-heaven root extracts or of its active constituents as natural herbicides.     

Nutrient and phytotoxic contributions of residue to soil in no-till continuous-corn ecosystems

Summary An understanding of no-till ecosystems is essential for increased acceptance of conservation tillage practices. The primary objective of the present research was to assess the nutrient contributions of leachates from decomposing corn residue to soil in continuous-corn no-till ecosystems. A secondary objective was to estimate the phytotoxic effects of these leachates on corn seedling growth. The effects of moisture, temperature, and resident and non-resident microflora on leachates recovered from decomposing surface-applied corn residue were also studied. Leachates were analyzed for organic C, total N, PO ₄ ^3– -P, acid and alkaline phosphatase activity, urease activity, and phytotoxic effects. Within the first 90 days of a 215-day field study 73%, 83%, and 60% of C, N, and P, respectively, were leached. In terms of nutrient concentration, this suggests two distinct phases of release of nutrients onto the soil: A high initial flux of nutrients that is followed by a low-concentration release. No phytotoxic effect of field leachates was observed. Acid and alkaline phosphatase activity was highest on days 39 and 47 whereas urease activity peaked on day 149. In laboratory studies, alterations in temperature or moisture had little effect on the leachate nutrient concentration, or phytotoxic or enzyme activity. Increasing amounts of organic C and N were extracted over time. No phytotoxic effects were expressed in the laboratory. Overall, it appears that the maximum leaching of nutrients occurs early in the decomposition process and that in no-till systems no phytotoxicity can be associated with decomposition of surface residues.Paper No. 11871 of the Purdue University Agricultural Experiment Station Series     

Experimental complexities in evaluating the allelopathic activities in laboratory bioassays: A case study

Soil is the major player in deciding allelopathic activities. A study was designed to examine experimental complexities in determining the allelopathic behavior of soil amended with water-soluble leachates from Chenopodium murale. Chenopodium murale interferes with the growth and establishment of crop seedlings. The present study examined the role of water-soluble organic substances, if any, in the shoot growth suppression of rice (Oryza sativa L.). Rice seeds were grown on C. murale leaf leachate-amended soil to investigate the phytotoxic effects of C. murale leachates. Any modification of C. murale phytotoxic activities was studied through using abiotic soil, activated charcoal and nitrogen (N) fertilization. Chemical and microbiological analysis of C. murale-amended soil was made to evaluate the role of soil components in C. murale phytotoxicity. Significant inhibition in the shoot growth of rice was observed when abiotic or biotic soil was amended with full-strength leaf leachate (T1) of C. murale compared to unamended soils. The inhibitory effect of T1 is maintained when rice seeds were placed on T1-amended soil after 0, 24 or 48 h; however, the inhibitory effects were eliminated when seeds were placed on amended soil after 72, 96 h or 1 wk of incubating soil with T1. Activated charcoal (1, 2 or 4 g) could not eliminate the inhibitory effects of T1-amended soil to the shoot length of rice. The phytotoxic effects of T1-amended soil to the shoot length of rice, however, were largely eliminated after the addition of N fertilization. Interference of C. murale leaf leachate to rice shoot growth could be due to number of effects that could be misconstrued as allelopathy effects.     

Effect of coal fly ash and co‐composted sewage sludge on emergence and early growth of cover crops

Abstract

Fly ash, a by‐product of coal combustion, is often stored in landfills. Stabilization of fly ash deposits can be hindered by phytotoxic levels of B and soluble salts in the ash. Two greenhouse studies were conducted with the objective of improving cover crop establishment on landfills containing fly ash. In one experiment, eight cover crop species were screened for tolerance to fly ash and fly ash‐amended soil, as measured by seedling emergence and early shoot growth. Hairy vetch, red clover, and tall fescue were identified as having the best potential for stabilization of fly ash deposits. Another experiment determined if amending fly ash with a co‐compost, produced from municipal refuse and sewage sludge, would improve the establishment and growth of tall fescue and Korean lespedeza. The co‐compost had no effect on fescue alone, but increased emergence and early growth of lespedesa and a fescue‐lespedeza mixture.     

Effects of water‐soluble constituents of plant residues on water uptake by seeds

Abstract

There has been strong support for the hypothesis that the adverse effects of plant residues on crop yields are due to phytotoxic compounds derived from these residues. This hypothesis is based largely on studies showing that, when compared with distilled water, aqueous extracts of plant residues have an adverse effect on seed germination and seedling growth. Because seed germination and seedling growth are reduced by a delay in germination resulting from slow uptake of water by seeds, we studied the possibility that the adverse effects of aqueous extracts of plant residues on seed germination and seedling growth might be at least partly due to water uptake by seeds being retarded by water‐soluble constituents of these residues. To test this possibility, we compared the rates of water uptake and germination of seeds of corn (Zea mays L.), soybean [Glycine max. (L.) Merrill], and wheat (Triticum aestivum L.) when these seeds were treated with distilled water and with aqueous extracts of corn, sorghum [Sorghum bicolor (L.) Moench], and wheat residues. We found that the rates of water uptake and germination of seeds treated with aqueous extracts of plant residues were appreciably slower than the corresponding rates for seeds treated with distilled water. This may be due to the water potentials of these extracts (ca. ‐50 kPa) because when seeds of corn, sorghum, and wheat were treated with a solution of polyethylene glycol 8000 having a water potential similar to that of the extracts of plant residues tested, the rates of water uptake and germination were also slower than the corresponding rates for seeds treated with distilled water. These observations suggest that the adverse effects of aqueous extracts of plant residues on seed germination and seedling growth when compared with distilled water may be partly due to constituents of these extracts inducing water potential effects that reduce water uptake by germinating seeds.     

茄子秸秆水提物自毒作用初探

试验研究茄子秸秆水提物自毒作用结果表明,茄子干秸秆水提物原液浓度为0 .0 15 g/ mL时明显抑制茄时明显抑制茄子胚根的生长,低浓度提取物原液对胚芽生长有一定促进作用,当其浓度增至0 .0 75g/ mL时明显抑制茄时茄子胚芽生长也受抑,表明茄子秸秆水提物对茄子生长有较强的自毒作用;水提物中醇溶性组分对茄子胚根、胚芽生长的影响与水提物原液表现一致,且对水培茄子幼苗生长有较强抑制作用,表明醇溶性组分中含有大量自毒物质。茄子幼苗根系活力随水提物中醇溶性组分浓度的增加而降低,植株对NO-3 、PO3 -4、K 、Mg2 和Ca2 等离子的吸收受阻,因而抑制离子的吸收是水提物中自毒物质发挥作用的重要因素之一。     

Synthesis and phytotoxic activity of ozonides

The [4 + 3] cycloaddition of the proper furans with the oxyallyl cation, generated in situ from 2,4-dibromopentan-3-one, produced a series of 8-oxabicyclo [3.2.1]oct-6-en-3-ones. Exposure of the oxabicycles to ozone afforded the corresponding 8,9,10,11-tetraoxatricyclo[5.2.1.1 (2,6)]undecan-4-ones in variable yields (7-100%). The phytotoxic properties of these ozonides (or 1,2,4-trioxolanes) and their oxabicycle precursors were evaluated as the ability to interfere with the growth of Sorghum bicolor and Cucumis sativus seedlings. Among oxabicycles, the highest inhibitory activity was shown by compounds possessing a alpha,beta-unsaturated carbonyl moiety. A differential sensitivity of the two crops was evident with ozonides. The most active compounds were also tested against the weed species Ipomoea grandifolia and Brachiaria decumbens. To the best of our knowledge, this is the first article describing ozonides as potential herbicides.     

Evaluation of Exponential Fertilization Technique for Cultivation of Turfgrass during Early Growth Period

The exponential fertilization method is based on the theory of supplying steady-state nutrition to young seedlings during the early, exponential growth stage. The objective of the research was to find the most effective method of fertilizing turfgrass during the early growth stage following seedling emergence. The field experiment was performed on turfgrass (tall fescue, Festuca arundinacea Schreb.) comparing a check (no fertilizer applied), two conventional fertilization techniques (equal additions and linearly increasing application rates over time) to the exponential additions fertilization method to test the relative effectiveness of this latter technique relative to conventional methods. Results show that the exponential growth period for fescue is the first 5 weeks following planting. Biomass accumulation, total nitrogen (N) concentration, and N content per seedling in turfgrass seedlings fertilized using the exponential addition fertilization technique were 32, 35, and 70% greater than those treated with traditional methods, respectively.     

不同生长环境下黄顶菊浸提液对多年生黑麦草萌发与生长的影响

为阐明黄顶菊入侵机制,本文在调查不同生境下黄顶菊居群特征的基础上,进一步采用植株浸提液生物测试的方法研究了不同生境、生长密度及替代植被下黄顶菊对多年生黑麦草的化感潜力。结果表明:黄顶菊的化感作用强弱与其入侵能力存在一定相关性,黄顶菊浸提液的化感潜力随浓度升高而增强;不同植株组织浸提液的化感潜力存在显著差异,表现为地下部分明显低于地上部分;不同生境下黄顶菊浸提液的化感潜力顺序为水边>果园>路边,50 g.L 1茎叶浸提液对多年生黑麦草发芽率化感效应敏感指数分别为2.83(水边)、1.31(果园)和0.71(路边);不同密度黄顶菊的茎叶化感潜力顺序为高、中密度区显著大于低密度区,50g.L 1浓度浸提液对多年生黑麦草发芽率化感效应敏感指数分别为3.91(高密度)、4.89(中密度)和0.29(低密度);根部浸提液的化感潜力顺序则相反。不同替代植被下茎叶浸提液的化感效应为混种>单种,而根系浸提液的化感效应敏感指数则差别不大。因此,黄顶菊不同组织器官化感活性物质分配不同,同时其化感效力能够适应环境条件而发生变化,这可能是造成黄顶菊在不同环境中入侵效果差异的原因之一。     

Assessment of allelopathic effects of residues of Flaveria bidentis (L.) Kuntze on wheat seedlings

Flaveria bidentis (L.) Kuntze, an invasive plant, poses a serious threat to the structure and function of the native ecosystem in Hebei Provience, China. However, little is known about the allelopathic activity of the residues of this plant species. In this study, the impact of the phytotoxicity of unburnt (UR) and burnt (BR) residues of the exotic invasive weed on the growth of wheat (Triticum aestivvm L.) was assessed. Extracts prepared from both UR and BR reduced the shoot length, root length and dry weight of wheat significantly compared with the control, thereby indicating the presence of some water-soluble allelochemicals in F. bidentis residues. Growth studies conducted in soil amended with UR and BR extracts or residues also revealed phytotoxic effects towards wheat. A significant amount of phenolics was detected in the residue extracts and in residue-incorporated soil. The phenolic content rose with increasing residue concentration, thereby showing their direct involvement in the observed growth inhibition. The inhibition of wheat growth by the burnt residue and its water extracts was similar to that of unburnt residue, so burning it is not a good way to eliminate the allelopathic effects of the residue of F. bidentis on native plants.     

毛红椿凋落叶水浸液自毒作用研究

为探究毛红椿凋落叶水浸液的自毒作用,采用生物测试法研究毛红椿凋落叶水浸液对自身种子发芽和幼苗生长的影响,并结合气相色谱质谱联用(GC-MS)技术分析凋落叶水浸液石油醚、乙醚、氯仿、甲醇4种不同极性萃取组分中存在的自毒物质。结果表明,凋落叶水浸液对毛红椿种子发芽及幼苗生长、存活率等均有抑制作用,浓度越高抑制作用越强,中浓度溶液(100 g·L^-1)对种子发芽和茎长达到显著抑制水平,对种子发芽率、发芽势、发芽指数、茎长的抑制率分别为18%、31%、31%和17%;低浓度溶液(10 g·L^-1)对根长的抑制达到显著水平,抑制率为25%。毛红椿凋落叶水浸液4种不同极性萃取组分中共鉴定到22种化合物,总体含酰胺类、长链脂肪酸、酚类、苯甲酸衍生物、烷烃类、腈类、二甲苯、松油烯及谷甾醇等物质,其中酰胺类、长链脂肪酸、酚类、苯甲酸衍生物成分可能为毛红椿自毒物质。本研究结果为探索毛红椿的濒危机制,促进毛红椿的实生更新提供了理论依据。     

Effects of aliphatic acids on seed germination and seedling growth in soil

Abstract

It is commonly assumed that the adverse effect of plant residues on crop yields is largely, or partly, due to phytotoxic compounds leached from these residues or produced by their decomposition, and it has been suggested that the phytotoxic compounds responsible for reduced crop yields are aliphatic acids such as acetic acid, butyric acid, and propionic acid. To test the validity of this hypothesis, we studied the effects of different amounts of acetic acid, butyric acid, and propionic acid on seed germination and seedling growth of corn (Zea mays L.), barley (Hordeum vulgare L.), and wheat (Triticum aestivum L.) in soils. The data obtained showed that the aliphatic acids tested had adverse effects on seed germination and seedling growth only when the amounts applied were much greater than the amounts reported to occur in soils treated with plant residues. We conclude that the adverse effect of plant residues on crop yields is not due to aliphatic acids derived from these residues.     

Control of pitch pine seed germination and initial growth exerted by leaf litters and polyphenolic compounds

We investigated the influence of three concentrations of water extracts of three leaf litter species (pitch pine, huckleberry and white oak) and a mixture of all litters on the germination of pitch pine seeds and initial seedling growth in a microcosm experiment. All three plant species are important components of the pine barrens ecosystems in New Jersey, where it has been seen that pine seedling recruitment occurs only after stand replacing fire or in disturbed sites, where surface organic soil horizons and leaf litter have been removed. Leaf litter extracts did not influence seed germination, but significantly reduced seedling growth at high concentrations. There was little difference between the leaf litter species in growth suppression. As charcoal is a natural residue on the forest floor following fire, its influence on growth suppression was examined; it has been shown to immobilize polyphenols. Charcoal removed the inhibitory effect of leaf litter extracts and allowed the fertilizer effect of nutrients leached from the leaves to enhance seedling growth, particularly at the higher concentration of litter extract used. Responses to litter extracts were compared to four pure phenolic compounds, catchecol, p-coumaric acid, p-hydroxybenzoic acid and tannic acid. None of these compounds suppressed pine seedling growth, suggesting that these phenolics are not allelopathic to pine seedlings. The results are discussed in the context of fire as a driving factor in these oligotrophic and seasonally dry ecosystems and the interactions between nutrient supply and allelopathic chemistry of different leaf litters.     

Horticultural and Floricultural Applications of Urban Wastes Originated Fertilizers

Different origin composts and a digestate from a biogas plant and their respective alkali soluble (SBO) and insoluble (IOR) fractions have been tested as organic fertilizers in growth media. The materials have been characterized by determination of pH, salinity, C, N, P, and K content. A preliminary evaluation of the possible phytoxicity has been performed by determination of the germination indexes of cress (Lepidium sativum), white mustard (Sinapsis alba) and radish (Raphanus sativus). Most of the materials did not promote the germination of the seeds. Notwithstanding these negative results, the materials were also used as partial peat substitute in a commercial substrate to test the growth of marigold (Tagetes patula), radish (Raphanus sativus), and spinach (Spinacia oleracea). The dimension and dry weight of the plants grown on the substrate mixed with the composts, the digestate or the SBOs were similar to those observed on the substrate. Moreover, most of the SOBs provoked the increase of the dry weight of the roots of the radishes, therefore an increase of the quality. The insoluble fractions (IOR) from the composts allowed a growth of the plants similar to that obtained with a commercial substrate. In contrast, the IOR obtained from the digestate was phytotoxic.     

Determination of phytotoxic soil aluminium by electroultrafiltration

The experiments address the questions of whether phytotoxic Al can be determined by electroultrafiltration (EUF). Spring barley (Hordeum vulgare) was grown in pot experiments on 28 soils differing widely in their characteristics. Al toxicity was measured in terms of root parameters and top growth. On soils rich in EUF extractable Al typical Al toxicity symptoms were found in roots and tops. EUF extractable Al obtained at the cathode (EUF-Al, cathode) was correlated with root fresh weight (R² = 0.554), root length (R² = 0.653), root diameter (R² = 0.729) and fresh weight of tops (R² = 0.681). The Al obtained at the anode was not correlated with any of these plant parameters. It is supposed that this anionic Al consists of non toxic organic Al complexes. Correlations between plant parameters and KCl-exchangeable Al were less close than those for EUF-Al (cathode). Correlations between soil pH and plant parameters were in between the correlations for exchangeable Al and EUF-Al (cathode).     

Effects of phenolic acids on seed germination and seedling growth in soil

Summary It is commonly assumed that the adverse effect of plant residues on crop yields is largely or partly due to phytotoxic compounds leached from these residues or produced by their decomposition. There has been substantial support for the hypothesis that the phytotoxic compounds responsible for reduced crop yields are phenolic acids such as p-coumaric acid, p-hydroxybenzoic acid, and ferulic acid. To test the validity of this hypothesis, we studied the effects of nine phenolic acids (caffeic acid, chlorogenic acid, p-coumaric acid, ellagic acid, ferulic acid, gallic acid, p-hydroxybenzoic acid, syringic acid, and vanillic acid) on (1) seed germination of corn (Zea mays L.), barley (Hordeum vulgare L.), oats (Avena sativa L.), rye (Secale cereale L.), sorghum [Sorghum bicolor (L.) Moench], wheat (Triticum aestivum L.), and alfalfa (Medicago sativa L.) on germination paper and soil, (2) seedling growth of alfalfa, oats, sorghum, and wheat on germination paper and soil, and (3) early plant growth of corn, barley, oats, rye, sorghum, and wheat in soil. The results showed that although the phenolic acids tested affected germination and seedling growth on germination paper, they had no effect on seed germination, seedling growth, or early plant growth in soil even when the amounts applied were much greater than the amounts detected in soil. We conclude that the adverse effect of plant residues on crop yields is not due to phenolic acids derived from these residues.     

Search for a standard phytotoxic bioassay for allelochemicals. Selection of standard target species

In the search for a standard bioassay of phytotoxicity for allelochemicals, 22 commercial varieties of eight plant species [four dicotyledons: lettuce (Compositae), carrot (Umbelliferae), cress (Cruciferae), tomato (Solanaceae); and four monocotyledons: onion (Liliaceae), barley, wheat, and corn (Gramineae)] proposed as models for the most common weed families have been tested at different pH and solution volumes per set conditions. Nine commercial varieties selected as standard target species (STS) were tested with standard commercial herbicides to ensure their sensitivity to phytotoxic compounds. Results are discussed to establish the proper growth requirements, and sensitivity of commercial seeds of STS and to find the most suitable commercial herbicides that allow comparison with an internal standard to validate the response of potential allelochemicals.