Wheat Coleoptile Growth Research Articles

Evaluation of the Allelopathic Potential of Leaf, Stem, and Root Extracts of Ocotea pulchella Nees et Mart.

Despite the increase in recent decades in herbicide research on the potential of native plants, current knowledge is considered to be low. Very few studies have been carried out on the chemical profile or the biological activity of the Brazilian savanna (Cerrado) species. In the study reported here, the allelopathic activity of AcOEt and MeOH extracts of leaves, stems, and roots from Ocotea pulchella Nees was evaluated. The extracts were assayed on etiolated wheat coleoptiles. The AcOEt leaf extract was the most active and this was tested on standard target species (STS). Lycopersicon esculentum and Lactuca sativa were the most sensitive species in this test. A total of eleven compounds have been isolated and characterized. Compounds 1, 2, 4, and 6 have not been identified previously from O. pulchella and ocoteol (9) is reported for the first time in the literature. Eight compounds were tested on wheat coleoptile growth, and spathulenol, benzyl salicylate, and benzyl benzoate showed the highest activities. These compounds showed inhibitory activity on L. esculentum. The values obtained correspond to the activity exhibited by the extract and these compounds may therefore be responsible for the allelopathic activity shown by O. pulchella.

Phytotoxins from Tithonia diversifolia

Tithonia diversifolia (Mexican sunflower) is a dominant plant of the Asteraceae family, which suggests it produces allelochemicals that interfere with the development of surrounding plants. The study described herein was conducted to identify the compounds that have phytotoxic activity in T. diversifolia extracts. Ethyl acetate extracts of the leaves, stems, and roots showed significant inhibition of wheat coleoptile growth, and the leaf extract had similar inhibitory effects to a commercial herbicide. Fourteen compounds, 12 of which were sesquiterpene lactones, have been isolated. Two sesquiterpene lactones are reported for the first time and were isolated as an inseparable mixture of 8β-O-(2-methylbutyroyl)tirotundin (4) and 8β-O-(isovaleroyl)tirotundin (5). Their structures were determined by spectroscopic analysis, including NMR techniques and mass spectrometry. The sesquiterpene lactones 1β-methoxydiversifolin (6), tagitinin A (7), and tagitinin C (8) were the major products identified. These compounds were active on etiolated wheat coleoptiles, seed germination, and the growth of STS and weeds. The phytotoxic activity shown by these sesquiterpene lactones indicates that they are the compounds responsible for the activity exhibited by the initial extracts.

Phytotoxic potential of Onopordum acanthium L. (Asteraceae).

Onopordum acanthium L. (Asteraceae) is a plant native to southern Europe and southwestern Asia, but it is invasive in disturbed areas and agricultural fields around the world, causing many agronomic problems by interfering with crops or preventing animals from grazing on pastures. Allelopathy could be one of the reasons that this plant has spread over different continents. The aim of the present study was to bioprospect O. acanthium leaf extracts through the isolation and purification of allelopathic secondary metabolites with phytotoxicity to explain their invasive behavior. Phytotoxic activity was tested using etiolated wheat coleoptiles. The most active extract was selected to perform a bioassay-guided isolation of two flavonoids, pectolarigenin (1) and scutellarein 4'-methyl ether (2), and two sesquiterpene lactones, elemanolide 11(13)-dehydromelitensin β-hydroxyisobutyrate (3) and acanthiolide (4). All compounds were isolated for the first time from O. acanthium, and acanthiolide (4) is described for the first time. Compound 3 strongly inhibited the growth of wheat coleoptiles and 1 showed an intermediate effect. The results indicate that these compounds could contribute to the invasion of O. acanthium in ecological systems and agricultural fields.

Detection of Fusarium langsethiae on wheat in Belgium

In 2010, the populations of Fusarium sp. and Microdochium sp. were monitored in Belgium and 16 strains were identified as Fusarium langsethiae on wheat in Belgium. The other species identified from the sampling were F. poae, F. tritinctum, F. graminearum, F. avenaceum and Microdochium nivale. The pathogenicity potential of the F. langsethiae strains was assessed via an in vitro coleoptile growth rate test on wheat seedlings and compared with strains of F. poae, F. tritinctum, F. graminearum and F. avenaceum known to cause Fusarium head blight. The results showed the ability of F. langsethiae to cause retardation in the wheat coleoptile growth rate, but at a lower rate than F. graminearum, F. avenaceum, F. poae and F. tricinctum. A test for mycotoxin production in vitro showed the ability of the four strains tested to produce T-2 and HT-2 toxins at a rate of up to 290 mg kg−1. This is the first report on the potential pathogenicity of F. langsethiae on wheat in Belgium, a species known to produce T-2 and HT-2 toxins, which are highly toxic for humans and animals.

Synthesis and phytotoxicity of 4,5 functionalized tetrahydrofuran-2-ones

In this work we report a versatile synthesis of fourteen γ-lactones all structurally related, nine of which are novel compounds, accomplished from the readily available furfural. The phytotoxic activity of the synthesized compounds was evaluated in vitro by the influence on the growth of wheat coleoptiles. The percentages of inhibition were mostly small and not statistically different from control after the third dilution (100 µmol L-1). In general, α,β-unsaturated lactones presented better activities than the saturated ones. The most active compounds presented 51, 68 and 76% of inhibition in 1000 µmol L-1. The results indicate that regardless of saturation, the presence of the γ-lactone moiety is important for the bioactivity, but their presence has no implications with potency.

Characterization of a wheat (Triticum aestivum L.) expansin gene, TaEXPB23, involved in the abiotic stress response and phytohormone regulation

Expansins are proteins that are generally accepted to be key regulators of cell wall extension and plant growth. We examined the expression pattern of TaEXPB23, a wheat (Triticum aestivum L.) expansin gene, under exogenous phytohormone and abiotic stress treatments. In addition, we evaluated its function in the tolerance to salt stress and high temperature (HT) by overexpressing it in transgenic tobacco plants. In subcellular localization assays, TaEXPB23 localized to the cell wall. Expression analysis demonstrated that the transcription pattern of TaEXPB23 corresponded to wheat coleoptile growth. Real-time RT-PCR analysis revealed that TaEXPB23 transcript expression was upregulated by exogenous methyl jasmonate (MeJA) and salt stress, but downregulated by exogenous gibberellins (GA₃), ethylene (ET), indole-3-acetic acid (IAA) and α-naphthlcetic acid (NAA). Overexpression of TaEXPB23 in tobacco (tabacum) conferred tolerance to salt stress by enhancing water retention ability (WRA) and decreasing osmotic potential (OP). However, transgenic plants overexpressing TaEXPB23 did not show any improvement in the tolerance to HT stress. These results suggested that TaEXPB23 is regulated by phytohormones and is involved in the regulation of salt stress tolerance.

Synthesis and Biological Activity ofN-AcylO-Indolylalkyl Ethanolamines

The plant-growth regulators, indole-3-carboxylic acids, were introduced into N-acyl ethanolamines, and a series of N-acyl O-indolylalkyl ethanolamines were prepared. Their biological activities to regulate rape hypocotyl elongation, cucumber cotyledon expansion and common wheat coleoptile growth were tested. The results indicate that the title compounds inhibited rape hypocotyl elongation, especially the indole-3-propionic acid derivatives, whose bioactivity was better than that of indole-3-acetic acid.

Drought tolerance through over-expression of the expansin gene TaEXPB23 in transgenic tobacco

Expansins are proteins that are the key regulators of wall extension during plant growth. To investigate the role of TaEXPB23, a wheat expansin gene, we analyzed TaEXPB23 mRNA expression levels in response to water stress in wheat and examined the drought resistance of transgenic tobaccos over-expressing TaEXPB23. We found that the expression of TaEXPB23 corresponded to wheat coleoptile growth and the response to water stress. The results also indicated that the transgenic tobacco lines lost water more slowly than the wild-type (WT) plants under drought stress; their cells could sustain a more integrated structure under water stress than that of WT. Other physiological and biochemical parameters under water stress, such as electrolyte leakage, malondialdehyde (MDA) level, photosynthetic rate, F v/ F m and ΦPSII, also suggested that the transgenic tobaccos were more drought resistant than WT plants.

Potencial alelopático do extrato foliar de Annona glabra L. (Annonaceae)

A. glabra cresce em áreas alagadas, formando aglomerados. Este comportamento pode indicar ocorrência de competição com outras espécies ou que existam processos alelopáticos. Neste estudo, os objetivos foram: a) avaliação do potencial alelopático de extratos foliares de A. glabra sobre a germinação e crescimento de outras espécies, e sobre o crescimento de coleóptilos de trigo e b) verificação da presença de grupos de substâncias nos extratos. Os testes qualitativos detectaram triterpenos, taninos e flavonóides. Foi realizada cromatografia de partição líquido:líquido com hexano e acetato de etila. A atividade das frações obtidas foi testada sobre de Lactuca sativa, Echinochloa crus-galli, Euphorbia heterophylla e Ipomoea grandifolia. A fração acetato de etila reduziu a porcentagem de germinação de L. sativa e atrasou o tempo médio de germinação de E. crus-galli além de afetar o crescimento de todas as espécies. Esta fração foi purificada em coluna de sílica, obtendo-se cinco frações (A, B, C, D e E). Para cada uma delas foram preparadas quatro concentrações (1000; 158; 79; 39,5 ppm). Os efeitos causados pelas frações foram avaliados com o teste de coleóptilo de trigo. A fração A estimulou o alongamento destes nas três menores concentrações, na maior foi inibitória, B inibiu nas três maiores, C inibiu apenas na maior e E não provocou efeito significativo.

Bioactivity of Ulva lactuca L. acetone extract on germination and growth of lettuce and tomato plants

Ethanol, butanol and acetone extracts of Ulva lactuca L. (Chlorophyta) at concentrations 10, 30, 100 and 300 ppm for each were applied to determine their biological activity under laboratory conditions using etiolated wheat's coleoptile growth bioassay. Acetone extract was the most active one and was selected to investigate the allelopathic potential on lettuce and tomato's seed germination and seedling growth. Nine free phenolic compounds were detected in the Ulva acetone extract by using HPLC analysis. Vanillin and p- coumaric acid was recorded as the abundant compounds while ferulic acid and salicylic acid existed in less amounts. Compared with the control, the germination of lettuce and tomato were stimulated by 5.8 and 21.5%, respectively, when treated with low concentration of acetone (30 ppm). In contrast, high concentration (300 ppm) retarded the germination and recorded high inhibition effect on lettuce (44.6%). Acetone extract, at 30 ppm, stimulated the radicle and plumule growth of lettuce by 10.6 and 27%, respectively, and tomato by 22.5 and 35%, respectively. Meanwhile, at 300 ppm, radicle and plumule growth of lettuce was greatly inhibited by 40.6 and 30%, respectively, whereas tomato was slightly inhibited. Moreover, roots appeared more sensitive to allelopathic effect than shoots.

Expansins and coleoptile elongation in wheat

Expansins are now generally accepted to be the key regulators of wall extension during plant growth. The aim of this study was to characterize expansins in wheat coleoptiles and determine their roles in regulating cell growth. Endogenous and reconstituted wall extension activities of wheat coleoptiles were measured. The identification of beta-expansins was confirmed on the basis of expansin activity, immunoblot analysis, and beta-expansin inhibition. Expansin activities of wheat coleoptiles were shown to be sensitive to pH and a number of exogenously applied factors, and their optimum pH range was found to be 4.0 to 4.5, close to that of alpha-expansins. They were induced by dithiothreitol, K(+), and Mg(2+), but inhibited by Zn(2+), Cu(2+), Al(3+), and Ca(2+), similar to those found in cucumber hypocotyls. An expansin antibody raised against TaEXPB23, a vegetative expansin of the beta-expansin family, greatly inhibited acid-induced extension of native wheat coleoptiles and only one protein band was recognized in Western blot experiments, suggesting that beta-expansins are the main members affecting cell wall extension of wheat coleoptiles. The growth of wheat coleoptiles was closely related to the activity and expression of expansins. In conclusion, our results suggest the presence of expansins in wheat coleoptiles, and it is possible that most of them are members of the beta-expansin family, but are not group 1 grass pollen allergens. The growth of wheat coleoptiles is intimately correlated with expansin expression, in particularly that of beta-expansins.

Biological Control of Fusarium Seedling Blight Disease of Wheat and Barley

ABSTRACT Fusarium fungi, including F. culmorum, cause seedling blight, foot rot, and head blight diseases of cereals, resulting in yield loss. In a screen for potential disease control organisms and agents, Pseudomonas fluorescens strains MKB 100 and MKB 249, P. frederiksbergensis strain 202, Pseudomonas sp. strain MKB 158, and chitosan all significantly reduced the extent of both wheat coleoptile growth retardation and wheat and barley seedling blight caused by F. culmorum (by 53 to 91%). Trichodiene synthase is a Fusarium enzyme necessary for trichothecene mycotoxin biosynthesis; expression of the gene encoding this enzyme in wheat was 33% lower in stem base tissue coinoculated with Pseudomonas sp. strain MKB 158 and F. culmorum than in wheat treated with bacterial culture medium and F. culmorum. When wheat and barley were grown in soil amended with either chitosan, P. fluorescens strain MKB 249, Pseudomonas sp. strain MKB 158, or culture filtrates of these bacteria, the level of disease symptoms on F. culmorum-inoculated stem base tissue (at 12 days post- F. culmorum inoculation) was >/=31% less than the level on F. culmorum-inoculated plants grown in culture medium-amended soil. It seems likely that at least part of the biocontrol activity of these bacteria and chitosan may be due to the induction of systemic disease resistance in host plants. Also, in coinoculation studies, Pseudomonas sp. strain MKB 158 induced the expression of a wheat class III plant peroxidase gene (a pathogenesis-related gene).

Effect of Ecdysterone on Morphological and Physiological Processes in Plants

In order to elucidate the physiological role of phytoecdysteroids in plants, we investigated the effects of exogenous ecdysterone (ECD) and phytohormones (IAA, GA3, and 24-epibrassinolide (EBL)) on the growth of wheat coleoptiles and Arabidopsis thaliana seedlings (wild-type ecotype Columbia (Col) and its det2 mutant), on α-amylase activity in the barley aleurone layer, and on the pigment content in the kidney bean senescent leaves. The range of effective ECD concentrations depended on the type of a reaction to be regulated. The regulation of growth processes was affected by a wide range of ECD concentrations (10–13–10–5 M), whereas some metabolic processes, such as the activation of α-amylase and the retardation of leaf yellowing, by a narrow range, that is, 10–9–10–7 M and 10–9–10–8 M, respectively. We noted the synergetic effect of ECD and IAA on coleoptile elongation, the antagonistic effect of ECD and EBL on coleoptile elongation, as well as the antagonistic action of ECD and GA3 on coleoptile elongation and α-amylase activity. The data obtained demonstrate that ECD is a physiologically active compound. ECD might be supposed to act as a source of sterols or a regulator of IAA and protein synthesis. The effects of this regulator seems to be brought about by its interaction with the EBL and GA3 receptors.

Phytotoxicity of metabolites produced by Pyrenophora semeniperda in liquid culture

Pyrenophora semeniperda was shown to produce heat stable, biologically active metabolites under agitated liquid culture conditions. Using a seedling bioassay it was shown that filtrates harvested from P.�semeniperda cultures had a significant impact on coleoptile length of both wheat and Bromus diandrus, but had no effect on seed germination. The relative toxicity of filtrates derived from several isolates of P. semeniperda and infiltrated into wheat leaves was highly correlated with the virulence of these isolates. A comparison of metabolites harvested from P. semeniperda and Pyrenophora teres grown under the same cultural conditions revealed that P.�teres did not affect wheat coleoptile growth, but affected the coleoptile elongation of B. diandrus, although less than filtrates produced by P. semeniperda. Culture filtrates harvested after 6 days were toxic to wheat and B.�diandrus and toxicity was maximal in filtrates derived from cultures that were 12 days old. Culture filtrates diluted to 1 in 20 produced symptoms in wheat seedlings, but only undiluted or 5 × concentrated filtrates produced symptoms on B.�diandrus seedling leaves. Plants older than first node stage (Z 31) were significantly less sensitive to filtrate than younger plants. A degree of host selectivity to the metabolites was observed since leaves of Gossypium hirsutum, Helianthus annuus, Lablab purpureus and Xanthium occidentale were unaffected by infiltrates.

Homobotcinolide: a biologically active natural homolog of botcinolide from Botrytis cinerea.

A novel natural product exhibiting biological activity was isolated from a strain of Botrytis cinerea that had infected raspberry fruit (Rubus ideaus). Liquid fermentation and bioassay-directed fractionation of the organism yielded a compound with molecular formula C22H38O8 that is trivially named homobotcinolide. It significantly inhibited etiolated wheat coleoptile growth. Greenhouse-grown bean, corn, and tobacco plants were also affected by exogenous application of homobotcinolide, severe chlorosis and necrosis being exhibited in corn. The compound is a polyhydroxylated nonalactone esterified with 4-hydroxy-2-decenoic acid.

Properties and Cost Effective Method for Production of the Antitumor Agent Duclauxin from Sporulating Penicillium herquei

Duclauxin, an antitumor agent, was isolated from sporulating Penicillium herquei (ATCC34665) grown on a medium of peanut hulls supplemented with potato starch solution (termed "Gostar"). The medium was inoculated with a sporulating subculture of P. herquei established on a 2% potato starch slurry supplemented with mineral salts. The P. herquei grew as well on Gostar as on an enriched medium. Duclauxin was isolated in crystalline form from Gostar-grown P. herquei. Comparison of costs of duclauxin obtained from inexpensive Gostar versus costly enriched media indicated that Gostar reduces production expenses. Duclauxin was not effective as an antibiotic against certain species of gram-positive and gram-negative bacteria, fungi, and viruses, but a concentration-dependent inhibition of wheat coleoptile growth was observed. Duclauxin was characterized by melting point, optical rotation, IR and NMR spectroscopy, MS and X-ray diffraction.

Botcinolide: A Biologically Active Natural Product fromBotrytis cinerea

A novel biologically active natural product was isolated from a strain of Botrytis cinerea found on cultivated raspberry fruit (Rubus ideaus) upon fermentation in a liquid medium. Following a bioassay-directed purification process, the final product was an amorphous solid with the molecular formula C20H34O8, and is trivially named botcinolide. It significantly inhibited etiolated wheat coleoptile growth at 10−3 and 10−4 M by 100 and 82% respectively, relative to the controls. Greenhouse-grown bean, corn, and tobacco plants were affected by treating with botcinolide, and exhibited chlorosis and severe necrosis at 10−2 and 10−3 M. The structure is a new hydroxylated nonalactone that is esterified with 4-hydroxy-2-octenoic acid.

In vitro auxin production by Balansia epichloë

Balansia epichloë, a systemic plant pathogen isolated from Sporobolus poiretii, was shown to produce the plant growth regulators 3-indole acetic acid, 3-indole ethanol, 3-indole acetamide and methyl-3-indole carboxylate when grown on a medium containing tryptophan. When grown on a tryptophan deficient medium 3-substituted indole derivatives were not detected. However, extracts of the medium in lower doses increased and in higher doses inhibited the growth of wheat coleoptiles.

THE LEVEL AND DISTRIBUTION OF PHENOLIC PLANT GROWTH INHIBITORS IN YAM TUBERS DURING DORMANCY

SummaryIn this study a possible role for batatasin‐type phenolic growth inhibitors in the control of dormancy and, therefore, the storage life of tubers of Dioscorea alata and D. esculenta, two economically important food yams, was investigated. After extraction, the level of endogenous growth inhibitory phenolics was estimated by a wheat coleoptile growth test and batatasins specifically determined by fluorescence spectroscopy and gas‐liquid chromatography. There was a gradual decrease in growth inhibitory phenolics in tubers of both species during dormancy and in D. alata this closely paralleled a decrease in batatasin content. It was found that batatasin‐type growth inhibitory phenolics accumulated rapidly in developing tubers just prior to the onset of dormancy and were assyrnetrically distributed, being concentrated in the proximal (head) region and in the peripheral zone just beneath the periderm. Gibberellin A3 treatment produced a promotion of the dormant period and a correlative rise in the growth inhibitory phenolic level. Effects of maleic hydrazide and ethylene chlorohydrin are also reported. The results are discussed in terms of the mechanism of dormancy control in these tubers and it is concluded that endogenous batatasin‐type phenolics are involved in this.

Relation of gibberellic acid-induced growth of wheat coleoptiles with indole acetic acid

Summary Gibberellic acid (GA3) induced elongation of wheat coleoptile sections and its relation with endogenous indole acetic acid was studied. Growth promotion by GA was reduced to half when oxidation of endogenous IAA was prevented by pretreatment of the coleoptiles with EDTA or a mixture of chlorogenic acid and 2,2′-dipyridyl. The effect of GA was reduced to ¼ when the endogenous methyleneoxindole (MeOx), an oxidation product of IAA, was made unavailable to GA3 during its action. External application of hydroxymethyloxindole (HMO), earliest oxidation product of IAA, helped GA to regain its full activity even when oxidation of endogenous IAA was inhibited. It is concluded that endogenous IAA, more precisely, its oxidation products, were necessary for GA in exhibiting its growth promoting activity on wheat coleoptile sections.