Organ-specific-active allelopathic substance in red pine needles

An organ-specific-growth inhibitory substance was isolated from an aqueous methanol extract of red pine needles and determined by spectral data as 1-mono(16-hydroxyhexadecanoyl)glycerol. This substance inhibited root growth of cress (Lepidium sativum L.) and barnyard grass (Echinochloa crus-galli (L.) Beauv) seedlings at concentrations greater than 0.01 and 0.03???M, respectively. The concentrations required for 50?% growth inhibition on roots of cress and barnyard grass were 0.16 and 3.4???M, respectively. However, the inhibitory activity of the substance on shoots of cress and barnyard grass was very weak. The endogenous concentration of 1-mono(16-hydroxyhexadecanoyl)glycerol in the pine needles was 4.6???mol?kg^?1. Two related compounds, 1-monohexadecanoylglycerol and 16-hydroxyhexadecanlic acid had no activity up to 1,000???M on cress roots and shoots. The effectiveness of 1-mono(16-hydroxyhexadecanoyl)glycerol on root growth inhibition and the occurrence of 1-mono(16-hydroxyhexadecanoyl)glycerol in pine needles suggest the substance may play an important role in the allelopathy of red pine. Root-specific-growth-inhibition by the substance may be one of the strategies for red pine to compete with neighboring plants for nutrients and space because root growth of competitive plants may be very important for their whole plant development.     

Identification of two phytotoxins, blumenol A and grasshopper ketone, in the allelopathic Japanese rice variety Awaakamai

Aqueous methanol extracts of the traditional rice (Oryza sativa) variety Awaakamai, which is known to have the greatest allelopathic activity among Japanese traditional rice varieties, inhibited the growth of roots and shoots of cress (Lepidium sativum), lettuce (Lactuca sativa), timothy (Phleum pratense), Digitaria sanguinalis, Lolium multiflorum and Echinochloa crus-galli. Increasing the extract concentration increased the inhibition, suggesting that the extract of Awaakamai contains growth inhibitory substances. The extract of Awaakamai was purified and two main growth inhibitory substances were isolated and determined by spectral data as blumenol A and grasshopper ketone. Blumenol A and grasshopper ketone, respectively, inhibited the growth of cress shoots and roots at concentrations greater than 10 and 30 μmol/L. The concentrations required for 50% growth inhibition on cress roots and shoots were 84 and 27 μmol/L, respectively, for blumenol A, and 185 and 76 μmol/L, respectively, for grasshopper ketone. These results suggest that blumenol A and grasshopper ketone may contribute to the growth inhibitory effect of Awaakamai and may play an important role in the allelopathy of Awaakamai.     

Allelopathy of red pine: isolation and identification of an allelopathic substance in red pine needles

Since red pine (Pinus densiflora Sieb. et Zucc.) often forms sparse forest floors where herbaceous plants do not grow well, allelopathy of red pine was investigated. A growth inhibitory substance was isolated from an aqueous methanol extract of red pine needles and determined by spectral data as abscisic acid-β-d-glucopyranosyl ester (ABA-GE). This substance inhibited root and shoot growth of cress and E. crus-galli seedlings at concentrations greater than 0.1 μM. The concentrations required for 50% growth inhibition on roots and shoots of cress were 0.23 and 0.61 μM, respectively, and those of E. crus-galli were 1.1 and 2.8 μM, respectively. The activity of ABA-β-d-glucosidase, which liberates free ABA from ABA-GE, in cress and E. crus-galli seedlings was 13–29 nmol mg⁻¹ protein min⁻¹. Endogenous concentration of ABA-GE in the pine needles was 4.1–21.5 μmol kg⁻¹ and the concentration in soil water of the pine forest was 2.5 μM. The effectiveness of ABA-GE on growth inhibition and the occurrence of ABA-GE in pine needles and soil water suggest ABA-GE may play an important role in the allelopathy of red pine resulting in the formation of sparse forest floors.     

Isolation and identification of a potent allelopathic substance in Bangladesh rice

Aqueous methanol extracts of Bangladesh rice (Oryza sativa L. cv. BR17) inhibited the growth of roots and shoots of cress (Lepidium sativum), lettuce (Lactuca sativa), alfalfa (Medicago sativa), timothy (Phleum pratense), Digitaria sanguinalis, Echinochloa crus-galli and Echinochloa colonum. Increasing the extract concentration increased the inhibition, suggesting that the BR17 may have growth inhibitory substances and possess allelopathic potential. The aqueous methanol extract of the BR17 was purified and a main inhibitory substance was isolated and determined by spectral data as 2,9-dihydroxy-4-megastigmen-3-one. This substance inhibited root and shoot growth of cress and E. crus-galli seedlings at concentrations greater than 0.03 and 3 μM, respectively. The concentrations required for 50% growth inhibition on cress roots and shoots were 0.22 and 0.47 μM, respectively, and on E. crus-galli roots and shoots were 36 and 133 μM, respectively. These results suggest that 2,9-dihydroxy-4-megastigmen-3-one may contribute to the growth inhibitory effect of BR17 and may play an important role in the allelopathy of BR17. Thus, Bangladesh rice BR17 may be potentially useful for weed management in a field setting. An erratum to this article can be found at     

Allelopathy and the allelothathic activity of a phenylpropanol from cucumber plants

The growth inhibitory effect of cucumber (Cucumis sativus L.) plants after crop harvested was investigated. Aqueous methanol extracts of the cucumber plants inhibited the growth of roots and shoots of cress (Lepidium sativum L.), lettuce (Lactuca sativa L.), alfalfa (Medicago sativa L.), ryegrass (Lolium multiflorum L.), timothy (Pheleum pratense L.), crabgrass (Digitaria sanguinalis L.), Echinochloa crus-galli (L.) Beauv and Echinochloa colonum (L.) Link, and increasing the extract concentration increased the inhibition. These results suggest that cucumber plants may possess allelopathic activity. The aqueous methanol extract of cucumber plants was divided into ethyl acetate and aqueous fractions, and the growth inhibitory activity of ethyl acetate fraction was greater than that of aqueous fraction. Thus, ethyl acetate fraction was further purified and a main allopathically active substance in the fraction was isolated and determined as (S)-2-benzoyloxy-3-phenyl-1-propanol by spectral data. This substance inhibited root and shoot growth of cress seedlings at concentrations greater than 10 μM, and the concentration required for 50% inhibition of root and shoot growth was 21 and 23 μM, respectively. These results suggest that (S)-2-benzoyloxy-3-phenyl-1-propanol may contribute to the growth inhibitory effect of cucumber plants and may play an important role in cucumber allelopathy. Thus, cucumber plants may be potentially useful for weed management in a field setting. An erratum to this article can be found at     

Isolation and identification of an allelopathic substance in Pisum sativum

The residue of peas (Pisum sativum L.) has allelopathic activity and the putative compound causing this inhibitory effect was isolated from a methanol extract of pea shoots. Chemical structure of this compound was determined by high-resolution MS, IR and 1H NMR spectral data as pisatin. Pisatin inhibited growth of cress (Lepidium sativum L.) and lettuce (Lactuca sativa L.) seedlings at concentrations greater than 10 and 30 microM, respectively. The doses required for 50% growth inhibition of roots and hypocotyls of cress were 61 and 91 microM, respectively, and those of lettuce were 78 and 115 microM, respectively. The concentration of pisatin in the pea shoots was 32.7 nmol x g(-1) fresh weight. The effectiveness of pisatin on growth inhibition in cress and lettuce, and its occurrence in pea shoots suggest that it may contribute to the growth inhibitory effect of pea residue, and may play an important role in pea allelopathy.     

A novel allelopathic substance, 13-epi-orthosiphol N,in Orthosiphon stamineus

Orthosiphon stamineus (Java tea) has been widely used as traditional herb and several bioactive compounds against animal cells have been isolated. However, no bioactive compound against plants has been reported. Therefore, we investigated possible allelopathic properties and substances in O. stamineus. Aqueous methanol extracts of O. stamineus inhibited root and hypocotyl growth of cress (Lepidium sativum) and lettuce (Lactuca sativa) seedlings. Increasing the extract concentration increased the inhibition, which suggests that O. stamineus may have allelopathic properties. When the extract was divided into an ethyl acetate and an aqueous fraction, the ethyl acetate fraction showed the stronger inhibitory effect. Thus, the ethyl acetate phase was further purified, and the main allelopathic substance was isolated and identified as 13-epi-orthosiphol N, a novel compound, by spectral data. 13-epi-Orthosiphol N inhibited root and hypocotyl growth of cress and lettuce at concentrations greater than 10 μmol/L. The concentrations required for 50% inhibition ranged from 41 to 102 μmol/L. These results suggest that 13-epi-orthosiphol N may be an allelochemical and main contributor to the growth inhibitory effect of O. stamineus and may have potential as a template for the development of new plant control substances.     

Allelopathic potential of Citrus junos fruit waste from food processing industry

The allelopathic potential of Citrus junos fruit waste after juice extraction was investigated. Aqueous methanol extracts of peel, inside and seeds separated from the fruit waste inhibited the growth of the roots and shoots of alfalfa (Medicago sativa L.), cress (Lepidium sativum L.), crabgrass (Digitaria sanguinalis L.), lettuce (Lactuca sativa L.), timothy (Pheleum pratense L.), and ryegrass (Lolium multiflorum Lam.). The inhibitory activity of the peel extract was greatest and followed by that of the inside and seed extracts in all bioassays. Significant reductions in the root and shoot growth were observed as the extract concentration was increased. The concentrations of abscisic acid-beta-d-glucopyranosyl ester (ABA-GE) in peel, inside and seeds separated from the C. junos fruit waste were determined, since ABA-GE was found to be one of the main growth inhibitors in C. junos fruit. The concentration was greatest in the peel, followed by the inside and seeds; there was a good correspondence between these concentrations and the inhibitory activities of the extracts. This suggests that ABA-GE may also be involved in the growth inhibitory effect of C. junos waste. These results suggested that C. junos waste may possess allelopathic potential, and the waste may be potentially useful for weed management.     

A potent allelopathic substance in cucumber plants and allelopathy of cucumber

A potent growth inhibitory substance was isolated from an aqueous methanol extract of cucumber (Cucumis sativus L. cv. Phung Tuong) plants and determined as (2S)-2,3-dihydro-2??-(4-hydroxy-3-methoxyphenyl)-7-methoxy-5-(1,2,3-trihydroxypropyl)benzofuran-3??-methanol (sisymbrifolin) by spectral data. Sisymbrifolin inhibited the growth of cress (Lepidium sativum) and Echinochloa crus-galli seedlings at concentrations greater than 3???M. Concentration of sisymbrifolin in the cucumber plants was the greatest among four growth inhibitory substances, (S)-2-benzoyloxy-3-phenyl-1-propanol, 9-hydroxy-4,7-megastigmadien-9-one, (6S,7E,9S)-6,9,10-trihydroxy-4,7-megastigmadien-3-one, and sisymbrifolin found in the cucumber, whereas growth inhibitory activity of 9-hydroxy-4,7-megastigmadien-9-one against cress and E. crus-galli was the greatest. Total activities of these substances (concentration of the substance/concentration required 50?% growth inhibition) were 14.4, 13.2, 8.5 and 10.7 for (S)-2-benzoyloxy-3-phenyl-1-propanol, 9-hydroxy-4,7-megastigmadien-9-one, (6S,7E,9S)-6,9,10-trihydroxy-4,7-megastigmadien-3-one and sisymbrifolin, respectively. These total activities were about 100-fold greater than those of phenolic acids, which are often mentioned as putative allelochemicals of plants. Thus, these substances may play important roles in the allelopathy of cucumber plants through the growth inhibition of neighboring plant species.     

Isolation and identification of a plant growth inhibitor from Tinospora tuberculata Beumee

Tinospora tuberculata Beumee has been used widely as a folk medicine and several bioactive compounds have been isolated. However, no herbicidal compound has been reported in this species. Therefore, we investigated the presence of phytotoxins in T. tuberculata. The aqueous methanol extracts of T. tuberculata inhibited the growth of roots and shoots of cress (Lepidum sativum L.), lettuce (Lactuca sativa L.), timothy (Phleum pratense L.) and barnyard grass (Echinochloa crus-galli (L.) Beauv.). The extract was then purified by several chromatographic runs with monitoring the inhibitory activity and the main phytotoxic substance was isolated. The chemical structure of the compound was determined by spectral data as syringin (4-[(1E)-3-Hydroxyprop-1-en-1-yl]-2,6-dimethoxyphenyl β-d-glucopyranoside). It inhibited the root and shoot growth of all test plant species at concentrations >10 µM. The concentrations required for 50 % inhibition of root and shoot growth of cress and lettuce ranged from 78.2 to 412 μM, and that of timothy and barnyard grass renged from 9.8 to 73.2 µM. Effectiveness of syringin on monocotyledonous (timothy and barnyard grass) plants was greater than that on dicotyledonous (cress and lettuce) plants. These results suggest that syringin may contribute to the allelopathic effect caused by the T. tuberculata extract.     

Isolation and identification of an allelopathic substance from peel of Citrus junos

The inhibitory effect of Citrus junos peel on plant growth using lettuce (Lactuca sativa L.) as a bioassay material was investigated, since the powder of the peel had been found to inhibit growth of weeds. Basic, neutral and acidic fractions were separated from the aqueous fraction obtained from the methanol extract of C. junos peel. All fractions inhibited the growth of lettuce seedlings, but by far the greatest inhibition was observed with the neutral fraction. Thus, the latter was further purified and an allelopathically active substance was isolated. The structure of the substance was determined from high-resolution MS and 1H and 13C NMR spectral data as abscisic acid-beta-D-glucopyranosyl ester (ABA-GE). ABA-GE inhibited hypocotyl and root growth of lettuce seedlings at concentrations greater than 0.3 microM, and the concentrations for 50% inhibition of hypocotyl and root growth were 2.3 and 1.4 microM, respectively. The effectiveness of ABA-GE on inhibition of growth and the occurrence of ABA-GE in the peel itself suggested that ABA-GE may play an important role in the allelopathic potential of C. junos peel. The peel may be potentially useful for weed management in a field setting.     

Isolation and identification of a potent allelopathic substance in rice root exudates

A search for growth inhibitors in rice root exudates was undertaken in order to clarify the allelopathic system in rice ( Oryza sativa L.). Rice seedlings inhibited the growth of cress ( Lepidium sativum L.) and lettuce ( Lactuca sativa L.) seedlings when the cress and lettuce were grown with rice seedlings. The putative compound causing the inhibitory effect of rice seedlings was isolated from their culture solution, and the chemical structure of the inhibitor was determined by spectral data as momilactone B. Momilactone B inhibited the growth of cress and lettuce seedlings at concentrations greater than 3 and 30 µ M , respectively. The concentration of momilactone B was 3.4 and 1.1 nmol per seedling in the culture solutions of husked and non-husked rice seedlings, respectively. These results suggest that rice seedlings may release momilactone B into the environment and the stress caused by the husk-treatment may increase the amount of momilactone B released. Thus, momilactone B may play an important role in rice allelopathy.     

Polyhydroxylated steroids from the soft coral Sinularia dissecta

A repeated silica gel column chromatography followed by HPLC purification on the methanol extract of marine soft coral Sinularia dissecta, resulted in the isolation of fifteen polyhydroxylated steroids (1-15), involving six new C-18 functionalized steroids, 3beta-acetoxy-1alpha,11alpha-dihydroxygorgost-5-en-18-oic acid (1), gorgost-5-en-1alpha,3beta,11alpha,18-tetrol (2), 18-acetoxy-1alpha,3beta,11alpha-trihydroxygorgost-5-ene (3), 24(S)-3beta-acetoxy-1alpha, 11alpha-dihydroxyergost-5-en-18-oic acid (4), 24(S)-ergost-5-en-1alpha,3beta,11alpha,18-tetrol (5), and dissectolide (6). The structures of the new compounds were determined on the basis of extensive spectroscopic data (IR, MS, (1)H and (13)C NMR, HMQC, HMBC, and NOESY) analysis. Compound 6 was found as an unusual sterol bearing a lactone functionality.     

Interactions between needles of Pinus resinosa and ectomycorrhizal fungi

Relatively little is known about the factors controlling ectomycorrhizal fungal communities. One possible factor is forest litter chemistry. In a series of experiments we demonstrated that the growth of ectomycorrhizal fungi able to colonize red pine ( Pinus resinosa Ait.) are differentially affected by red pine needles and needle chemical components. For example, water extracts of pine needles stimulated the growth of Suillus intermedius (Smith & Thiers) Smith & Thiers and inhibited the growth of Amanita rubescens Pers. Catechin and epicatechin gallate, components of the water extract, acted similarly to the extract. The volatile compounds α- and β-pinene also had differential effects on the growth of the various species of ectomycorrhizal fungi. Our results suggest that forest litter chemistry has the potential differentially to affect the growth of ectomycorrhizal fungal species and so could affect the structure of ectomycorrhizal fungal communities.     

彩色豆马勃子实体的化感作用及其化感物质的分离鉴定

彩色豆马勃能与松树、桉树形成外生菌根,研究其次生代谢产物对植物的影响具有重要意义。用水、乙醇和丙酮抽提彩色豆马勃的子实体,发现这些抽提物对稗草和水稻幼苗生长有极显着的抑制作用。丙酮抽提物对狼尾草和油菜幼苗生长有抑制作用。子实体的丙酮抽提物用硅胶柱色谱分离得到2个纯化合物,可鉴定为豆马勃内酯(Pisolactone)和麦角甾醇。该2个化合物在400μg·ml^-1浓度下均显着抑制稗草幼苗根生长。豆马勃内酯在100μg·ml^-1浓度下仍然极显着抑制稗草幼苗根生长.     

Allelopathic substances in Pueraria thunbergiana

Leaves of Pueraria thunbergiana possess allelopathic activity and the putative compounds causing this growth inhibitory effect were isolated from their aqueous methanol extract. The chemical structures of these growth inhibitors were determined by high-resolution MS and 1H NMR spectral data as cis,trans-xanthoxin and trans,trans-xanthoxin. cis,trans-Xanthoxin and trans,trans-xanthoxin inhibited the root growth of cress (Lepidium sativum L.) seedlings at concentrations greater than 0.3 and 3 microM, respectively. The doses required for 50% inhibition on the cress roots were 1.1 and 14 microM for cis,trans- and trans,trans-xanthoxin, respectively. The concentrations of cis,trans- and trans,trans-xanthoxin in P. thunbergiana leaves were 51.4 and 72.5 ng g(-1) fresh weight, respectively. The effectiveness of cis,trans- and trans,trans-xanthoxin on the growth inhibition and the occurrence of both xanthoxins in P. thunbergiana suggest that xanthoxins may contribute to the growth inhibitory effect of P. thunbergiana, and may play an important role in the allelopathy of P. thunbergiana after being released into the soil.     

Allelopathy is involved in the formation of pure colonies of the fern Gleichenia japonica

The fern Gleichenia japonica is one of the most widely distributed fern and occurs throughout East to South Asia. The species often dominates plant communities by forming large monospecific colonies. However, the potential mechanism for this domination has not yet been described. The objective of this study was to test the hypothesis that allelochemicals are involved in the formation of G. japonica colonies. An aqueous methanol extract of G. japonica inhibited the growth of seedlings of garden cress (Lepidium sativum), lettuce (Lactuca sativa), ryegrass (Lolium multiflorum) and timothy (Phleum pratense). Increasing extract concentration increased the inhibition. These results suggest that G. japonica contain allelopathic substances. The extract was then purified by several chromatographies with monitoring the inhibitory activity and two growth inhibitory substances causing the allelopathic effect were isolated. The chemical structures of the two substances were determined by spectral data to be a novel compound 3-O-β-allopyranosyl-13-O-β-fucopyranosyl-3β-hydroxymanool (1) and 18-O-α-l-rhamnopyranosyl-(1→2)-β-d-glucopyranosyl-13-epitorreferol (2). These compounds inhibited the shoot and root growth of garden cress, lettuce, alfalfa (Medicago sativa), timothy, ryegrass and barnyardgrass (Echinochloa crus-galli) at concentrations greater than 0.1–1.0 mM. The concentrations required for 50% growth inhibition of root and shoot growth of these test plants ranged from 0.72 to 3.49 mM and 0.79 to 3.51 mM for compounds 1 and 2, respectively. Concentration of compounds 1 and 2 in soil under the pure colony of G. japonica was 4.9 and 5.7 mM, respectively, indicating concentrations over those required for 50% growth inhibition are potentially available under monocultural stands of these ferns. Therefore, these compounds may contribute to the allelopathic effects caused by presence of G. japonica and may thus contribute to the establishment of monocultural stands by this fern.     

Isolation and identification of potent allelopathic substances in rattail fescue

Aqueous methanol extracts of rattail fescue (Vulpia myuros) inhibited the growth of roots and shoots of cress (Lepidium sativum), lettuce (Lactuca sativa), alfalfa (Medicago sativa), timothy (Phleum pratense), Digitaria sanguinalis and Lolium multiflorum. Increasing the extract concentration increased the inhibition, suggesting that rattail fescue may have growth inhibitory substances and possess allelopathic potential. The aqueous methanol extract of rattail fescue was purified and two main inhibitory substances were isolated and identified by spectral data as (−)-3-hydroxy-β-ionone and (+)-3-oxo-α-ionol. Both substances inhibited root and shoot growth of cress at concentrations greater than 0.3 μM. The concentrations required for 50% growth inhibition on root and shoot growth of cress, lettuce, alfalfa, timothy, D. sanguinalis and L. multiflorum were 2.7–19.7 μM for (−)-3-hydroxy-β-ionone, and 2.1–34.5 μM for (+)-3-oxo-α-ionol. The concentration of (−)-3-hydroxy-β-ionone and (+)-3-oxo-α-ionol, respectively, in rattail fescue was 7.8 and 3.7 μg g⁻¹ fresh weight. Considering the endogenous level and the inhibitory activity, (−)-3-hydroxy-β-ionone and (+)-3-oxo-α-ionol may work as allelopathic substances in rattail fescue through the growth inhibition of neighboring plant species.     

芦蒿不同浸提物化感活性的比较研究

采用水、甲醇、乙醇、丙酮和乙酸乙酯等不同溶剂对整株芦蒿进行浸提,并用生菜和紫花苜蓿作为受试植物,对不同浸提物进行了化感活性的比较研究。5种不同溶剂的芦蒿浸提物对种子的萌发率和幼苗生长均表现出化感潜势,与对照组相比,0.005 g/mL的芦蒿甲醇提取物对生菜和紫花苜蓿种子的萌发具有轻微的促进作用,当浓度达到0.04 g/mL以上时,对生菜和紫花苜蓿种子的萌发和幼苗生长均具有不同程度的抑制作用（p〈0.05）。不同浓度的提取液对植物的化感作用强度不同,对种子萌发率、根长、芽长均有不同程度的影响。根据比较,甲醇溶剂提取物的化感活性最强,其是深入研究芦蒿化感物质有效的提取剂。     

氮素增加条件下丛枝菌根真菌对陆稻和无芒稗相互作用的调节

采用盆栽方法研究了增氮条件下丛枝菌根真菌(AMF)对无芒稗(Echinochloa crusgallivar.mitis L.)和陆稻(Oryza sativa L.)相互作用的调节.结果表明:在单种条件下,无芒稗的菌根侵染率增加,陆稻的菌根侵染率降低;无AMF和接种AMF处理陆稻的生物量分别提高13.48%和42.35%,总磷吸收分别提高2.55%和4.07%,总氮吸收分别提高62.09%和30.35%;无芒稗的生物量分别提高15.65%和20.24%,总磷吸收分别提高4.06%和3.88%,总氮吸收分别提高30.35%和15.10%.在混种条件下,无芒稗的菌根侵染率增加,而陆稻无显著变化;无AMF和接种AMF的无芒稗与陆稻的生物量比值降低,总氮吸收比值无显著变化,无AMF处理的总磷吸收比值增加,而接种AMF处理降低.表明增氮条件下AMF提高了无芒稗对陆稻的竞争.