Factors Affecting Dalapon Absorption and Translocation in Johnsongrass

The factors affecting the absorption and translocation of ¹⁴C-dalapon (2.2-dichloropropionic acid) in johnsongrass were studied. Johnsongrass [Sorghum halepense (L.) Pers.] was first pot-grown in a greenhouse and then treated and placed in controlled-environment chambers. Absorption of ¹⁴C-dalapon into johnsongrass leaves and subsequent translocation occurred continuously within the plant during a 48-h period after treatment. Gas chromatographic analysis of johnsongrass extracts showed that the dalapon molecule was translocated intact. Absorption and translocation of ¹⁴C-dalapon increased as the droplet volume of the diluent was increased from 0.2 to 5.0 μl per treated spot. At 21 and 32°C, translocation of ¹⁴C-dalapon from a 2-cm treated leaf section into the plant was greater at 100% than at 35% relative humidity. At 38°C, translocation was greater at 35% than at 100% relative humidity. The addition of 0.5% surfactant to the dalapon solution increased translocation under all environmental conditions studied. The addition of 0.1 M KH₂PO₄ to dalapon-surfactant solutions increased ⁴-dalapon translocation under high temperature (38°C), especially at 35% relative humidity.     

Effects of Orally Administered Bovine Lactoferrin on the Faecal Enterobacteriaceae of SPF Mice Fed Milk

Several phytotoxic metabolites, including a novel compound chaetoglobosin O, were isolated from Cylindrocladium floridanum Sobers et Seymore. The structure of chaetoglobosin O, including its absolute configuration, was determined by a spectroscopic analysis and chemical correlation. Purified chaetoglobosins A, C, and O showed potent growth-inhibition activity against alfalfa seedlings.     

Transgenic plants of ramie (Boehmeria nivea Gaud.) obtained by Agrobacterium mediated transformation

A regeneration and transformation protocol for ramie (Boehmeria nivea Gaud.) is presented. Regeneration was obtained from leaf discs placed on solid B-5 medium (Gamborg et al. 1968) containing adequate concentrations of auxin and cytokinin. Co-cultivation of leaf discs with Agrobacterium tumefaciens and subsequent regeneration resulted in transgenic plants as shown by Southern blot and analysis of expression of the GUS-marker gene.     

Deoxyradicinin and 3-epideoxyradicinol production by the sunflower pathogen Alternaria helianthi

The phytotoxic compound deoxyradicinin, a metabolite of Alternaria helianthi, was isolated from naturally infected leaves of sunflower (Helianthus annuus). The production of this toxin in liquid culture together with 3-epideoxyradicinol is discussed. Production of deoxyradicinin by liquid cultures was observed to decrease after successive sub-culture of the fungus on solid medium. All 10 accessions of Helianthus tested were sensitive to deoxyradicinin although some quantitative differences between lines were noted. Evidence is presented for the metabolism of deoxyradicinin by host leaf tissue.     

Constitutive knox1 gene expression in dandelion (Taraxacum officinale, Web.) changes leaf morphology from simple to compound

Seed plants with compound leaves constitute a polyphyletic group, but studies of diverse taxa show that genes of the class 1 KNOTTED-LIKE HOMEOBOX (KNOX1) family are often involved in compound leaf development. This suggests that knox1 genes have been recruited on multiple occasions during angiosperm evolution (Bharathan et al. in Science 296:1858–1860, 2002). In agreement with this, we demonstrate that the simple leaf of dandelion (Taraxacum officinale Web.) can be converted into a compound leaf by the constitutive expression of heterologous knox1 genes. Dandelion is a rosette plant of the family Asteraceae, characterised by simple leaves with deeply lobed margins and endogenous knox1 gene expression. Transgenic dandelion plants constitutively expressing the barley (Hordeum vulgare L.) hooded gene (bkn3, barley knox3) or the related bkn1 gene, developed compound leaves featuring epiphyllous rosettes. We discuss these results in the context of two current models of compound leaf formation.Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users.     

Identification of an allelopathic compound from Ailanthus altissima (Simaroubaceae) and characterization of its herbicidal activity

Aqueous extracts of Ailanthus altissima bark and foliage were previously shown to be toxic to other plants. Using bioassay-directed fractionation, I isolated the phytotoxic compound from A. altissima root bark and identified it to be ailanthone, a quassinoid compound having molecular mass of 376. Ailanthone was highly phytotoxic, with concentrations of 0.7 ml/L causing 50% inhibition of radicle elongation in a standardized bioassay with garden cress (Lepidium sativum) seeds. Ailanthone exhibited potent pre- and postemergence herbicidal activity in greenhouse trials. Postcmergence activity was especially striking; even the lowest application rate (0.5 kg/ha) caused complete mortality of five of the seven plant species tested within 5 d of treatment. In contrast, the highest application rate (8 kg/ha) did not cause any detectable injury to A. altissima seedlings, indicating the presence of a protective mechanism in the producer species to prevent autotoxicity. Ailanthone was rapidly detoxified in field soil as a result of microbial activity. Applications of ailanthone equivalent to 0.5 and 4.0 kg/ha completely lost their phytotoxicity within ≤5 d when incubated in the presence of nonsterile soil. When incubated with sterile soil under identical conditions, however, ailanthone remained highly phytotoxic throughout the 21-d duration of the investigation. The high level of postemergence herbicidal activity in conjunction with its rapid biodegradation in soil suggest ailanthone may have potential for development as a natural-product herbicide.     

L'azione fitotossica dell'Irpexil (acetidrossamoilacetato di metile) sulle piante superiori. Nota prima: Azione brachizzante ed inibizione mitotica

Abstract

The phytotoxic action of Irpexil (Methylacethydroxamoilacetate) on higher plants. 1: action on growth and mitotic inhibition.—The fungal secondary metabolite Irpexil (Methylacethydroxamoilacetate) shows a rather marked inhibiting effect on the growth of mono-and dycotiledons seedlings. Both length and fresh weight of the axial parts are affected, particularly in wheat and pea seedlings. The inhibiting effect is at least partially due to the antimitotic activity of this compound; Irpexil does not seem to interfere at any stage of the mitotic cycle, at least at moderate concentrations (up to 70 ppm).     

Substituent Effect on Photosynthesis of N2-α-Substituted Benzyl-N4-alkyl-2,4-diamino-6-chloro-s-triazines and Their Phytotoxic Property

The influence of substituents on the activities of a series of N²-α-substituted benzyl-N⁴-alkyl-2,4-diamino-6-chloro-s-triazines as inhibitors of photosystem II (PSII) was examined, and the phytotoxic differences between them and atrazine, as to the photosynthesis in leaf disks, mesophyll cells, intact chloroplasts and broken chloroplasts of spinach, and as to seedling-growth, were discussed. The inhibitory activity of the N²-α,α-dimethylbenzyl-N⁴-ethyl derivative (6), which was comparable on that of atrazine, was lower than those of the N²-α-alkylbenzyl analogues (1 ~5). The N⁴-?-alkyl-N²-α- methylbenzyl derivatives, in spite of the carbon length of the alkyl group, exhibited more potent activity than atrazine, but an a α β substitution of the N⁴-n-alkyl group caused a decrease in the activity with a few exceptions. These data may imply that the space of the binding site on PSII surrounding both the N² and N⁴ amino groups is relatively large. The binding between the receptor site and the N⁴ amino group, however, is easily influenced by a slight structural change in an inhibitor. The herbicidal compounds, N²-α-methylbenzyl-A^⁴-ethyl (1), A^²-α,α-dimethylbenzyl-N⁴-1-methylpropyl (30) and N²-α-methylbenzyl-N⁴,N⁴-diethyl (42) derivatives, exhibited potent inhibitory activity in the seedling growth test under dark/light conditions, whereas atrazine was very poor. The inhibitory activity of compound (1) toward photosynthesis was poor with leaf disks, compared to atrazine, whereas, the order of their activities was the reverse for plant preparations such as abaxial epidermis peeled leaf disks, mesophyll cells, intact chloroplasts and broken chloroplasts. It was indicated that a change in the phytotoxic symptom in the whole plant assay would be correlated to the permeability of the compound through the plant membrane(s).     

A Potent Phytotoxic Substance in Aglaia odorata Lour.

Aglaia odorata Lour . (Meliaceae) was found to have very strong allelopathic activity and a bioherbicide PORGANIC^? was developed from its leaf extracts. However, the phytotoxic substances causing the strong allelopathic activity of the plants have not yet been determined. Therefore, we investigated allelopathic properties and phytotoxic substances in A. odorata. Aqueous EtOH extracts of A. odorata leaves inhibited root and shoot growth of garden cress (Lepidum sativum), lettuce (Lactuca sativa), alfalfa (Medicago sativa), timothy (Phleum pratense), ryegrass (Lolium multiflorum), and Echinochloa crus‐galli with the extract concentration‐dependent manner. The extracts were then purified and a major phytotoxic substance with allelopathic activity was isolated and identified by spectral data as rocaglaol. Rocaglaol inhibited the growth of garden cress and E. crus‐galli at concentrations > 0.3 and 0.03 μm , respectively. The concentrations required for 50% inhibition ranged from 0.09 to 2.5 μm . The inhibitory activity of rocaglaol on the weed species, E. crus‐galli, was much greater than that of abscisic acid. These results suggest that rocaglaol may be a major contributor to the allelopathic effect of A. odorata and bioherbicide PORGANIC^?.     

A morphological revision of the genus Herbertus S.Gray (Herbertaceae,Marchantiophyta) in Africa,including the East African islands

Abstract

The genus Herbertus S.Gray in Africa and the East African islands is revised. The division of the genus into two broad species complexes centred on H. dicranus (Tayl.ex Gottsche et al.) Trev. and H. juniperoideus (Sw.) Grolle is confirmed. H. capensis (Steph.) Sim, H. capillaris (Steph.) H. doggeltianus (Steph.) Demaret, H. lobatus (Steph.) Demaret, H. mascarenicus (Steph.) S.Arn., H. mollis (Steph.) Dusén, H. stuhlmannii (Steph.) Demaret and Schisma kilimandjarense Steph. are synonymous with H. dicranus. H. grossevittatus (Steph.) S.Arn. ex Grolle is synonymous with H. juniperoideus. Three new species are described: H. spicatus N.G.Hodgetts sp. nov., which is related to H. juniperoideus and appears close to the neotropical H. pensilis, with long, narrow leaf lobe apices and a sheathing leaf base; H. mauritianus N.G.Hodgetts sp. nov., also related to H. juniperoideus, has fewer basal slime papillae and the vitta bifurcating lower down; and H. pocsii N.G.Hodgetts sp. nov., which is related to H. dicranus but has setaceous leaf lobe apices composed of long, narrow cells. The relationships of the taxa and patterns of distribution, taking account of recent molecular work, are discussed.     

Allelopathic effect of <Emphasis Type="Italic">Nepeta meyeri</Emphasis> Benth. extracts on seed germination and seedling growth of some crop plants

In order to evaluate the allelopathic potential of Nepeta meyeri Benth., the effects of aqueous extracts (0.125, 0.25, 0.5, 1, 2.5 and 5%) prepared from roots and leaves of N. meyeri were studied on the seed germination and seedling growth of several economically important crops (barley, wheat, canola, safflower, and sunflower). Both the root and leaf extracts of N. meyeri caused a general phytotoxic effect on the seed germination and seedling growth of barley and sunflower at all concentrations. However, both the root and leaf extracts significantly increased the seedling growth of wheat, especially at the lower concentrations 0.125, 0.25 and 0.5%, whereas the higher concentrations had a neutral effect. The seed germination and the seedling growth of canola and safflower were also generally improved by both extracts, especially at lower concentrations. However, these advantages were not observed at higher concentrations, at which the extracts mostly had a phytotoxic effect on canola and safflower. The Allelopathic activity of N. meyeri depended on whether the extract was derived from the leaf or root parts of the plant. The maximum allelopathic effect occurred with leaf extracts. The results demonstrate that the aqueous extracts from N. meyeri have allelopathic potential and should be evaluated as an allelopathic species, presenting a risk or advantage to seed germination and seedling growth of crop or weed plants.     

Allelopathic effect of Schinus molle essential oils on wheat germination

Gas chromatography-flame ionisation detection (GC-FID) and gas chromatography–mass spectrometry (GC–MS) analyses of the essential oils of leaves and fruits of the ornamental Shinus molle L. were reported and their allelopathic effect on wheat (Triticum aestivum L.) was evaluated. Qualitative and quantitative differences between fruit and leaf oils were observed. Both oils were rich in monoterpene hydrocarbons and the major constituents were limonene and β-phellendrene (35.9–65.4%), α-phellendrene (24.3–20.1%), myrcene (12.8–7.7%) and α-pinene (5.9–1.7%) for fruits and leaves, respectively. Both essential oils showed a dose-dependent allelopathic activity on wheat germination and radicle elongation with leaf oil being the more phytotoxic.     

Metabolomics approach to investigate phytotoxic effects of Wedelia trilobata leaves,litter and soil

Although release and accumulation of plant metabolites from plant into soil can influence allelopathy, little information is known about metabolite changes that occur in leaf, litter and soil. In this study, seed germination bioassay tests and metabolomics analysis were performed to investigate the phytotoxic effects and metabolic variations (measured as buckets) in the ethanolic extracts of leaf, leaf litter and soil of Wedelia trilobata. Increasing the ethanolic extracts concentration of all extracts significantly inhibited Lactuca sativa germination rate (GR), shoot height (SH) and root length (RL). Soil exerted the strongest inhibition but contained the lowest number of buckets relative to those of leaf and leaf litter extracts. An overlap overview on the metabolome revealed a poor bucket overlap and redundancy among the leaf, leaf litter and soil extracts. Canonical correspondence analysis concluded that the SH of L. sativa was more sensitive to leaf litter extract and the leaf extract exerted a strong influence on the GR and RL of L. sativa. Multivariate analysis suggested that the metabolome of the leaf, leaf litter and soil differ substantially. Finally, putative identification using MS/MS data demonstrated various plant metabolites with phytotoxic effects that can contribute to the allelopathy of W. trilobata.     

Bioactivity studies of oxysporone and several derivatives

Recently oxysporone, a phytotoxic dihydrofuropyranone, was isolated along with two closely related compounds, afritoxinones A and B, from liquid cultures of Diplodia africana, an invasive fungal pathogen of Phoenicean juniper. In this study, eight derivatives were hemisynthesized and assayed for their phytotoxic and antifungal activities in comparison to the parent compound. Each compound was tested on non-host plants and on four destructive plant pathogens such as Athelia rolfsii, Diplodia corticola, Phytophthora cinnamomi and P. plurivora. The results on the phytotoxic activity showed that the dihydrofuropyranone carbon skeleton and both the double bond the hydroxy group of dihydropyran ring appeared to be structural features important in conferring activity. Although the data concerning the antifungal activity did not allow to extract any structure–activity relationships, it should be underlined that the conversion of oxysporone into the corresponding 4-O-benzoyl derivative led to a compound showing a good antifungal activity towards three out of the four organisms tested.     

Inhibition of tomato (Solanum lycopersicum L.) root growth by cyanamide is due to altered cell division, phytohormone balance and expansin gene expression

Cyanamide (CA) has been reported as a natural compound produced by hairy vetch (Vicia villosa Roth.) and it was shown also to be an allelochemical, responsible for strong allelopathic potential in this species. CA phytotoxicity has been demonstrated on various plant species, but to date little is known about its mode of action at cellular level. Treatment of tomato (Solanum lycopersicum L.) roots with CA (1.2 mM) resulted in inhibition of growth accompanied by alterations in cell division, and imbalance of plant hormone (ethylene and auxin) homeostasis. Moreover, the phytotoxic effect of CA was also manifested by modifications in expansin gene expression, especially in expansins responsible for cell wall remodeling after the cytokinesis (LeEXPA9, LeEXPA18). Based on these results the phytotoxic activity of CA on growth of roots of tomato seedlings is likely due to alterations associated with cell division.     

Phytotoxic activity of caulerpenyne from the Mediterranean invasive variety of Caulerpa racemosa: a potential allelochemical

Allelopathy has been postulated as a factor in the colonisation success of Caulerpa racemosa var. cylindracea, an introduced chlorophyte alga which has become invasive in the Mediterranean Sea. In order to reveal their possible phytotoxic activity, secondary metabolites were isolated from a population growing in the Gulf of Naples (Italy) and tested on leaf tissue of the native seagrass Cymodocea nodosa, which often co-occurs with Caulerpa in nature. The seaweed metabolites were identified by ¹H and ¹³C NMR analysis and leaf portions of C. nodosa were exposed to crude diethyl ether extract and purified compounds in the laboratory, under controlled conditions of irradiance and temperature for a period of 144 h. Eventual changes in the photosynthetic performance of the seagrass tissue following the treatment were tested by monitoring its optimal quantum yield with a pulse amplitude modulated (PAM) fluorometer. One of the identified compounds, caulerpenyne, showed a phytotoxic effect, while the other purified metabolites did not reveal any effect at the assayed concentrations. Thus, our results seem to suggest a possible allelopathic activity of caulerpenyne, which may play a role in the successful competition of the invasive C. racemosa var. cylindracea with native macrophytes, such as seagrasses.     

Phytotoxic Metabolites Isolated from Scolecotrichum graminis Fuckel

Two new cercosporins, (+)-isocercosporin (1) and (+)-14-acetylisocercosporin (2), were isolated from culture filtrates of Scolecotrichum graminis Fuckel, which is the causal fungus of a leaf streak disease in orchardgrass. The structure of each was elucidated by spectroscopic analysis, and (+)-isocercosporin (1) is the first isolated enantiomer of known (?)isocercorporin (8b). Compounds 1 and 8b had higher phytotoxic activity than that of (+)-cercosporin (a), an atropisomer of 8b. The results of the bioassay suggest that the phytotoxic activity of cercosporins depends on the relative configuration, and not on the absolute configuration. In addition, three phenol compounds, 1-(2,4-dihydroxy-6-methylphenyl)ethanone (3), isosclerone (4), and fraws-3,4-dihydro-3,4,8-trihydroxy-1(2H)-naphthalenone (5), were isolated as minor components and identified. Compound 3 was isolated for the first time as a natural products.     

A single-base deletion mutation in <Emphasis Type="Italic">SlIAA9</Emphasis> gene causes tomato (<Emphasis Type="Italic">Solanum lycopersicum</Emphasis>) <Emphasis Type="Italic">entire</Emphasis> mutant

The entire (e) locus of tomato (Solanum lycopersicum L.) controls leaf morphology. Dominant E and recessive e allele of the locus produce pinnate compound and complex reduced leaves. Previous research had indicated that SlIAA9, an Aux/IAA gene, was involved in tomato leaf morphology. Down-regulation of SlIAA9 gene by antisense transgenic method decreased the leaf complex of tomato and converted tomato compound leaves to simple leaves. The leaf morphology of these transgenic lines was similar with leaf morphology of tomato entire mutant. In this paper, we report that a single-base deletion mutation in the coding region of SlIAA9 gene results in tomato entire mutant phenotypes.