Bioactive compounds from the parasitic plant Arceuthobium vaginatum inhibit Haemonchus contortus egg hatching.

The aim of this study was to assess the in vitro ovicidal activity of an ethyl acetate extract from Arceuthobium vaginatum (EtOAc-E) and their subfractions (AvR5-AvR14) against Haemonchus contortus using the egg hatching inhibition (EHI) test. The EtOAc-E and subfractions were tested at 0.12-2.00 and at 0.015-2.0 mg/mL, respectively. Distilled water and methanol (2%) were used as negative controls and Thiabendazole (0.10 mg/mL) as a positive control. Treatments with a dependent effect on concentration were subjected to regression analysis to determine the effective concentrations (EC50 and EC90). The major secondary compounds present in the extract and subfractions were identified by high performance liquid chromatography (HPLC). The EtOAc-E and AvR9 exhibited the best ovicidal effect recording 97.5 and 100% of EHI at 0.25 mg/mL, respectively. The EtOAc-E and AvR9 displayed an EC50= 0.12 and 0.08 mg/mL, respectively. The HPLC analysis in the EtOAc-E and bioactive fractions indicated the presence of a polyphenol, glycosylated flavanones, quercetin glucoside, cinnamates, coumarin, cinnamic acid derivative, ferulic acid, coumarate, naringenin, protocatechuic acid and naringin. Results demonstrated that A. vaginatum extract and fraction is able to inhibit the egg hatch process of H. contortus and could be a viable option for the control of small ruminant haemonchosis.

Highly degenerate plastomes in two hemiparasitic dwarf mistletoes: Arceuthobium chinense and A. pini (Viscaceae).

MAIN CONCLUSION: The leafless and endophytic habitat may significantly relax the selection pressure on photosynthesis, and plastid transcription and translation, causing the loss/pseudogenization of several essential plastid-encoding genes in dwarf mistletoes. Dwarf mistletoes (Arceuthobium spp., Viscaceae) are the most destructive plant parasites to numerous conifer species worldwide. In this study, the plastid genomes (plastomes) of Arceuthobium chinense Lecomte and A. pini Hawksworth and Wiens were sequenced and characterized. Although dwarf mistletoes are hemiparasites capable of photosynthesis, their plastomes were highly degenerated, as indicated by the smallest plastome size, the lowest GC content, and relatively very few intact genes among the Santalales hemiparasites. Unexpectedly, several essential housekeeping genes (rpoA, rpoB, rpoC1, and rpoC2) and some core photosynthetic genes (psbZ and petL), as well as the rpl33 gene, that is indispensable for plants under stress conditions, were deleted or pseudogenized in the Arceuthobium plastomes. Our data suggest that the leafless and endophytic habit, which heavily relies on the coniferous hosts for nutrients and carbon requirement, may largely relax the selection pressure on photosynthesis, as well as plastid transcription and translation, thus resulting in the loss/pseudogenization of such essential plastid-encoding genes in dwarf mistletoes. Therefore, the higher level of plastome degradation in Arceuthobium species than other Santalales hemiparasites is likely correlated with the evolution of leafless and endophytic habit. A higher degree of plastome degradation in Arceuthobium. These findings provide new insights into the plastome degeneration associated with parasitism in Santalales and deepen our understanding of the biology of dwarf mistletoes.

Inflorescence evolution in Santalales: integrating morphological characters and molecular phylogenetics.

PREMISE OF THE STUDY: The sandalwood order (Santalales) includes members that present a diverse array of inflorescence types, some of which are unique among angiosperms. This diversity presents not only interpretational challenges but also opportunities to test fundamental concepts in plant morphology. Here we used modern phylogenetic approaches to address the evolution of inflorescences in the sandalwood order. METHODS: Phylogenetic analyses of two nuclear and three chloroplast genes were conducted on representatives of 146 of the 163 genera in the order. A matrix was constructed that scored nine characters dealing with inflorescences. One character, "trios", that encompasses any grouping of three flowers (i.e., both dichasia and triads) was optimized on samples of the posterior distribution of trees from the Bayesian analysis using BayesTraits. Three nodes were examined: the most recent common ancestors of (A) all ingroup members, (B) Loranthaceae, and (C) Opiliaceae, Santalaceae s.l., and Viscaceae. KEY RESULTS: The phylogenetic analysis resulted in many fully resolved nodes across Santalales with strong support for 18 clades previously named as families. The trios character was not supported for nodes A and C, whereas it was supported for node B where this partial inflorescence type is best described as a triad. CONCLUSIONS: Essentially every major inflorescence type can be found in Santalales; however, the dichasium, a type of partial inflorescence, is rarely seen and is not plesiomorphic for the order. In the family Erythropalaceae, inflorescences are mostly in small, axillary fascicles or cymes. Successive families show both cymose and racemose types and compound systems (e.g., thyrses). Inflorescences in Amphorogynaceae and Viscaceae are not dichasial and in general are difficult to compare to "standard" inflorescences.

Dwarf mistletoe infection in jack pine alters growth-defense relationships.

Trees utilize a combination of chemical and anatomical defenses against a myriad of attacking organisms. However, persistent pathogen infection that alters resource acquisition may impact growth and defense relationships, which could have consequences for tree resistance. We characterized systemic chemical and anatomical changes in jack pine (Pinus banksiana) in response to infection by the parasitic plant dwarf mistletoe (Arceuthobium americanum) and identified how the growth-defense relationship is altered due to infection severity. Our study found that the growth and defense relationship in jack pine was altered due to infection and that chemical defenses in the phloem received a relatively higher priority than radial growth and anatomical defenses. Chemical defenses in the phloem had a non-linear relationship with infection severity with increasing concentrations of monoterpenes in trees with moderate infection and decreasing concentrations at high infection. In contrast, both radial growth and vertical resin duct production decreased with increasing infection severity. While constitutive resin duct counts and many monoterpene compound concentrations were positively correlated, this relationship was not maintained in infected trees. Furthermore, radial growth and basal area increment was positively correlated with resin duct production and monoterpene concentration in non-infected trees but had fewer relationships in severely infected trees. We conclude that while both chemical and anatomical defenses may be used as indicators for potential resistance to biotic stress in pines, changes in resource allocation patterns between these defenses after infection will likely have consequences on tree resistance to subsequent biotic attacks.

Behavioral Evidence for Host Transitions in Plant, Plant Parasite, and Insect Interactions.

Specialized herbivorous insects have the ability to transition between host plant taxa, and considering the co-evolutionary history between plants and the organisms utilizing them is important to understanding plant insect interactions. We investigated the role of a pine tree parasite, dwarf mistletoe (Arceuthobium spp.) M. Bieb. Santalales: Viscaceae, in mediating interactions between Neophasia (Lepidoptera: Pieridae) butterflies and pine trees, the butterflies' larval hosts. Mistletoe is considered the butterflies' ancestral host, and the evolutionary transition to pine may have occurred recently. In Arizona, United States, we studied six sites in pine forest habitats: three in Neophasia menapia (Felder and R. Felder, 1859) habitat and three in Neophasia terlooii Behr, 1869 habitat. Each site contained six stands of trees that varied in mistletoe infection severity. Butterfly behavior was observed and ranked at each stand. Volatile compounds were collected from trees at each site and analyzed using gas chromatography-mass spectroscopy. Female butterflies landed on or patrolled around pine trees (i.e., interacted) more than males, and N. terlooii interacted more with pine trees than N. menapia. Both butterfly species interacted more with tree stands harboring greater mistletoe infection, and N. terlooii interacted more with heavily infected tree stands than did N. menapia. The influence of mistletoe on Neophasia behavior may be mediated by differences in tree volatiles resulting from mistletoe infection. Volatile profiles significantly differed between infected and uninfected pine trees. The role of mistletoe in mediating butterfly interactions with pines has implications for conservation biology and forest management, and highlights the importance of understanding an organism's niche in an evolutionary context.

Conocimiento local del género Arceuthobium en un área natural protegida del centro de México / Local knowledge of Arceuthobium genus in a natural protected area of the centre of Mexico

El género Arceuthobium (muérdago enano) es una de las principales plagas en los bosques templados de México, con antecedentes de uso medicinal y forrajero. El objetivo de este trabajo fue documentar el conocimiento local sobre los usos del muérdago enano en el Área Natural Protegida Nevado de Toluca, México, bajo las perspectivas emic y etic, a través de la etnobotánica. Mediante entrevistas se identificó que ambas especies (A. vaginatum y A. globosum) son conocidas como muérdago y forman parte de la flora del bosque; sin embargo, los entrevistados desconocen los efectos negativos dentro de los ecosistemas forestales de esta plaga. Destacan los usos lúdicos, como juguete y tinta, y los medicinales para el tratamiento de afecciones respiratorias y del sistema nervioso, siendo éste el primer registro para dicho género localmente. Se requieren estudios que validen el conocimiento local para su inclusión en programas locales de manejo de plagas forestales.

Arceuthobium (dwarf mistletoe) genus is one of the main pests in temperate forests of Mexico, with records of medicinal and forage uses. The objective of this work was to document local knowledge regarding uses of dwarf mistletoe in the Natural Protected Area Nevado de Toluca, Mexico, under emic and etic perspectives, through ethnobotany. Throughout interviews it was identified that both species (A. vaginatum and A. globosum) are known as mistletoe and they are part of flora in forest, however, interviewees are not aware of negative effects within forest ecosystems of this pest. It stands out ludic uses as a toy and ink, and medicinal ones for treatment of respiratory diseases and nervous system, being this the first record for such genus locally. Studies are required to validate the local knowledge for its inclusion in local programmes for management of forest pests.

Use of GC/MS to identify chemical constituents and cytotoxic activity of the leaves of Phoradendron mucronatum and Phoradendron microphyllum (Viscaceae).

Phoradendron mucronatum and P. microphyllum are plants that found in tropical and subtropical areas, used in traditional medicine and popularly known as mistle-thrush. The aim of this study was to identify the chemical constituents of different leaf extracts from P. mucronatum and P. microphyllum and assess cytotoxic activity against strains from a human tumour cells. Extracts obtained with hexane, dichloromethane, chloroform and ethyl acetate from the leaves were analysed by gas chromatography coupled with mass spectrometry (GC-MS) and the cytotoxicity was assessed by the MTT method (bromide (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide)). The tested human tumour cells were NCI-H292 (human pulmonar mucoepidermoid carcinoma), MCF-7 (human breast adenocarcinoma) and HEp-2 (epidermoid carcinoma of the larynx). Analysis by GC/MS of the extracts from leaves of P. microphyllum and P. mucronatum detected 51 different compounds, such as alkaloids, diterpenes, triterpenes, sterols, alcohols, aldehydes, fatty acids and hydrocarbons. In the cytotoxic evaluation, hexane and ethyl acetate extracts from the leaves P. microphyllum inhibited cell growth of NCI-H292 strains (72.97%) and HEp-2 (87.53%), respectively. The extracts of P. mucronatum species showed an inhibitory effect towards NCI-H292 (83.19%/hexane), MCF-7 (88.69%/dichloromethane) and HEp-2 (93.40%/hexane). The extracts showed cytotoxic activity against the tested strains, especially the P. mucronatum, which presented the highest percentages of inhibition of cell growth.

Use of GC/MS to identify chemical constituents and cytotoxic activity of the leaves of Phoradendron mucronatum and Phoradendron microphyllum (Viscaceae)

ABSTRACT Phoradendron mucronatum and P. microphyllum are plants that found in tropical and subtropical areas, used in traditional medicine and popularly known as mistle-thrush. The aim of this study was to identify the chemical constituents of different leaf extracts from P. mucronatum and P. microphyllum and assess cytotoxic activity against strains from a human tumour cells. Extracts obtained with hexane, dichloromethane, chloroform and ethyl acetate from the leaves were analysed by gas chromatography coupled with mass spectrometry (GC-MS) and the cytotoxicity was assessed by the MTT method (bromide (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide)). The tested human tumour cells were NCI-H292 (human pulmonar mucoepidermoid carcinoma), MCF-7 (human breast adenocarcinoma) and HEp-2 (epidermoid carcinoma of the larynx). Analysis by GC/MS of the extracts from leaves of P. microphyllum and P. mucronatum detected 51 different compounds, such as alkaloids, diterpenes, triterpenes, sterols, alcohols, aldehydes, fatty acids and hydrocarbons. In the cytotoxic evaluation, hexane and ethyl acetate extracts from the leaves P. microphyllum inhibited cell growth of NCI-H292 strains (72.97%) and HEp-2 (87.53%), respectively. The extracts of P. mucronatum species showed an inhibitory effect towards NCI-H292 (83.19%/hexane), MCF-7 (88.69%/dichloromethane) and HEp-2 (93.40%/hexane). The extracts showed cytotoxic activity against the tested strains, especially the P. mucronatum, which presented the highest percentages of inhibition of cell growth.

Diverse early dwarf mistletoes (Arceuthobium), ecological keystones of the Eocene Baltic amber biota.

PREMISE OF THE STUDY: Extant dwarf mistletoes (Arceuthobium M. Bieb., Viscaceae) are hemiparasites with complex roles in nature. They are one of the most severe pests in northern hemisphere conifer forests, but they also enhance the structural complexity and species diversity of the forests. Here, we describe the first pre-Miocene macrofossils of dwarf mistletoes. The fossils from Eocene Baltic amber provide new insights into the morphological evolution of the Arceuthobium lineage and its paleobiogeography. METHODS: The amber inclusions were investigated with light microscopy and compared with extant Viscaceae and to historic descriptions of lost Baltic amber fossils with affinities to Viscaceae. KEY RESULTS: Six fossil species of the Arceuthobium lineage, A. johnianum comb. nov., A. mengeanum comb. nov., A. conwentzii sp. nov., A. groehnii sp. nov., A. viscoides comb. nov. and A. obovatum sp. nov., occurred in source forests of Baltic amber, representing the oldest macrofossil evidence of dwarf mistletoes. They share morphological features of their bracts, internodes, fruits, and stomata with extant Arceuthobium. Differences from extant dwarf mistletoes, such as the perianth merosity, the nonfusion of squamate bracts and presence of oblanceolate expanded leaves, indicate their affiliation to an ancient lineage of the genus. CONCLUSIONS: The occurrence of six species of dwarf mistletoes in a single amber deposit suggests Arceuthobium was a keystone taxon of the Baltic amber source area. As in extant conifer forests, they probably influenced the structural complexity of the forest, not only leading to more open woodlands but also increasing species diversity, at least at a microhabitat scale.

Comparative inflorescence development in selected Andean Santalales.

PREMISE OF THE STUDY: Loranthaceae, Santalaceae, and Viscaceae are the most diversified hemiparasitic families of Santalales in the Andes. Their partial inflorescences (PIs) vary from solitary flowers, or dichasia in most Santalales, to congested floral groups along articles in most Viscaceae. The atypical articled inflorescences in Phoradendreae (Viscaceae), a phylogenetic novelty restricted to this tribe, have been variously described as racemes, spikes, fascicles, or as intercalary inflorescences, but no developmental studies have been performed to compare them with the construction of PIs across Santalales. METHODS: We used standard light microscopy and scanning electron microscopy to record the inflorescence development in members of Phoradendreae (Viscaceae) in comparison to those in species of Aetanthus, Gaiadendron, Oryctanthus, Passovia, and Peristethium (Loranthaceae) and Antidaphne (Santalaceae). KEY RESULTS: Morphological and developmental comparisons as well as optimization onto a phylogenetic framework indicate that individual inflorescences in Santalales are indeterminate and are formed by axillary cymose PIs. The latter correspond to dichasia, either simple, compound, or variously reduced by abortion of lateral flowers, abortion of the terminal flower, or loss of bracteoles. CONCLUSIONS: Dichasia are plesiomorphic in Santalales. These results favor the interpretation that inflorescences in Phoradendreae are formed by the fusion of serial dichasia (=floral rows) with the main inflorescence axis via syndesmy. We compared this interpretation with the competing one based on the co-occurrence of collateral and serial floral buds.

High-resolution transcript profiling reveals shoot abscission process of spruce dwarf mistletoe Arceuthobium sichuanense in response to ethephon.

Arceuthobium (dwarf mistletoes) are hemiparasites that may cause great damage to infected trees belonging to Pinaceae and Cupressaceae. Currently, dwarf mistletoe control involves the use of the ethylene-producing product ethephon (ETH), which acts by inducing dwarf mistletoe shoot abscission. However, the process by which ETH functions is mostly unknown. Therefore, the transcriptome of the ETH-exposed plants was compared to non-exposed controls to identify genes associated with the response to ethephon. In this study, the reference transcriptome was contained 120,316 annotated unigenes, with a total of 21,764 ETH-responsive differentially expressed unigenes were identified. These ETH-associated genes clustered into 20 distinctly expressed pattern groups, providing a view of molecular events with good spatial and temporal resolution. As expected, the greatest number of unigenes with changed expression were observed at the onset of abscission, suggesting induction by ethylene. ETH also affected genes associated with shoot abscission processes including hormone biosynthesis and signaling, cell wall hydrolysis and modification, lipid transference, and more. The comprehensive transcriptome data set provides a wealth of genomic resources for dwarf mistletoe communities and contributes to a better understanding of the molecular regulatory mechanism of ethylene-caused shoots abscission.

Population structure of a vector-borne plant parasite.

Parasites are among the most diverse groups of life on Earth, yet complex natural histories often preclude studies of their speciation processes. The biology of parasitic plants facilitates in situ collection of data on both genetic structure and the mechanisms responsible for that structure. Here, we studied the role of mating, dispersal and establishment in host race formation of a parasitic plant. We investigated the population genetics of a vector-borne desert mistletoe (Phoradendron californicum) across two legume host tree species (Senegalia greggii and Prosopis velutina) in the Sonoran desert using microsatellites. Consistent with host race formation, we found strong host-associated genetic structure in sympatry, little genetic variation due to geographic site and weak isolation by distance. We hypothesize that genetic differentiation results from differences in the timing of mistletoe flowering by host species, as we found initial flowering date of individual mistletoes correlated with genetic ancestry. Hybrids with intermediate ancestry were detected genetically. Individuals likely resulting from recent, successful establishment events following dispersal between the host species were detected at frequencies similar to hybrids between host races. Therefore, barriers to gene flow between the host races may have been stronger at mating than at dispersal. We also found higher inbreeding and within-host individual relatedness values for mistletoes on the more rare and isolated host species (S. greggii). Our study spanned spatial scales to address how interactions with both vectors and hosts influence parasitic plant structure with implications for parasite virulence evolution and speciation.

Anti-Inflammatory Properties of Flavone di-C-Glycosides as Active Principles of Camellia Mistletoe, Korthalsella japonica

The chemical components and biological activity of Camellia mistletoe, Korthalsella japonica (Loranthaceae) are relatively unknown compared to other mistletoe species. Therefore, we investigated the phytochemical properties and biological activity of this parasitic plant to provide essential preliminary scientific evidence to support and encourage its further pharmaceutical research and development. The major plant components were chromatographically isolated using high-performance liquid chromatography and their structures were elucidated using tandem mass spectrometry and nuclear magnetic resonance anlysis. Furthermore, the anti-inflammatory activity of the 70% ethanol extract of K. japonica (KJ) and its isolated components was evaluated using a nitric oxide (NO) assay and western blot analysis for inducible NO synthase (iNOS) and cyclooxygenase (COX)-2. Three flavone di-C-glycosides, lucenin-2, vicenin-2, and stellarin-2 were identified as major components of KJ, for the first time. KJ significantly inhibited NO production and reduced iNOS and COX-2 expression in lipopolysaccharide-stimulated RAW 264.7 cells at 100 μg/mL while similar activity were observed with isolated flavone C-glycosides. In conclusion, KJ has a simple secondary metabolite profiles including flavone di-C-glycosides as major components and has a strong potential for further research and development as a source of therapeutic anti-inflammatory agents.

Solvent effects on phytochemical constituent profiles and antioxidant activities, using four different extraction formulations for analysis of Bucida buceras L. and Phoradendron californicum.

BACKGROUND: The present investigation evaluated 4 different solvent compositions for their relative capacity to extract total phenolic and total flavonoid (TF) components of the leaves, trunks, and stems of Bucida buceras L. (Combretaceae), and the stems of Phoradendron californicum (Viscaceae), plus mesquite and oak species endemic to the Southwestern United States, northern Mexico, and tropical regions of Central and South America, as well as to profile the composition of these plant materials and to measure their antioxidant capacity. METHODS: The total phenolic content of plant material used in the present investigation was measured using the Folin-Ciocalteau assay. Total flavonoids were assayed by AlCl3 and 2,4-dinitrophenylhydrazin colorimetry. Nitroblue tetrazolium was utilized for scavenging of superoxide anion, and in vitro antioxidant activity was evaluated using the 2, 2-diphenyl-1-picrylhydrazyl and Ferric Reducing/Antioxidant Power assays. RESULTS: Phytochemical screening of each plant extract evaluated revealed the following major results: (1) No evidence of alkaloids for each of the extraction phases tested was detected in the hexanic, ethanolic, or aqueous phases of Bucida buceras and Phoradendron californicum (oak and mesquite); (2) Analysis of the hexane phase of B. buceras and P. californicum (mesquite) extracts revealed the presence of carotenes, triterpenes/steroids, and lactonic groups; (3) Analysis of the ethanol and aqueous extraction phases for both plants revealed the presence of a diverse range of compounds, including tripterpenes/steroids, lactonics groups, saponins, phenols/tannins, amines and/or amino acids, and flavonoids/anthocyanins; and (4) The highest total phenolic and flavonoid content were observed in P. californicum (oak): 523.886 ± 51.457 µg GAE/mg extract and 409.651 ± 23.091 µg/mg of extract for methanol and aqueous fractions, respectively. The highest flavonoid content was 237.273 ± 21.250 µg PNE/mg extract in the acetone extract of Bucida buceras stems; while the flavonol content (260.685 ± 23.031 µg CE/mg extract) was higher in the ethanol extract of P. californicum (oak). The acetone extract of B. buceras trunk extract showed the highest levels of DPPH radical-scavenging activity (IC50 = 4.136 ± 0.446 µg/mL) and reducing power (4928.392 ± 281.427 µM AAE/mg extract). The highest superoxide radical scavenging activity (IC50) was 55.249 ± 9.829 µg/mL, observed in acetone extracts of B. buceras leaves. CONCLUSIONS: The results of the present investigation demonstrated the effects of extraction solvent on phenolic and flavonoid content yield-and antioxidant activities by Bucida buceras and Phoradendron californicum. The present investigation further revealed that Bucida buceras exhibited optimal antioxidant capacity when acetone was used as extraction solvent; and the highest yield of phenols and flavonoids were obtained from the P. californicum oak, using methanol and aqueous solvents, respectively.

Mechanistic Evidence of Viscum schimperi (Viscaceae) Antihyperglycemic Activity: From a Bioactivity-guided Approach to Comprehensive Metabolite Profiling.

Diabetes mellitus is possibly the world's largest growing metabolic disorder. Effective treatment of diabetes is increasingly dependent on active constituents of medicinal plants capable of controlling hyperglycemia as well as its secondary complications. Viscum schimperi Engl. is a plant growing in Saudi Arabia and known for its antidiabetic activity. The potential antidiabetic activity of its methanol extract as well as its chloroform, n-butanol, and the remaining water fractions was evaluated in streptozotocin-induced diabetic rats at two dose levels. The antidiabetic activity was assessed through the determination of fasting blood glucose level, insulin levels, area under the curve (AUC) in oral glucose tolerance test, glucose absorption in isolated rat gut assay, and glucose uptake by psoas muscle. Moreover, large-scale untargeted metabolite profiling of methanol extract was performed via UPLC-PDA and qTOF-MS (ultra-performance liquid chromatography photodiode array detection and quadrupole time-of-flight mass spectrometry) respectively, to explore its chemical composition and standardization of its extract. Multivariate statistical analysis including principal component analysis and orthogonal projection to latent structures discriminant analysis was used to determine bioactives in its fractions. In conclusion, oleanane triterpenes and O-caffeoyl quinic acid conjugates were the major compounds that might account for antihyperglycemic effect of the plant.

Morfoanatomia foliar de phoradendron obtusissimum(miq ) eichler (viscaceae), "ka'a votyre'y", utilizado con fines medicinales en una comunidad de Colonia Independencia, Paraguay / Leaf morphoanatomy of Phoradendron obtusissimum(Miq) Eichler (V iscaceae), "ka'avotyre'y", used for medicinal purposes in a community of Colonia Independencia, Paraguay

Resumen: El "ka'avotyre'y", Phoradendron obtusissimum (V iscaceae), es una especie empleada con fines medicinales en Paraguay para tratar enfermedades hepáticas. El presente trabajo se desarrolló dentro del marco del proyecto "Conservación, fortalecimiento y uso sostenible de la flora de Itá Azul y San Gervasio, Colonia Independencia, Reserva de Recursos Manejados Ybytyruzu, Paraguay" y tuvo por objetivo describir la morfoanatomía de P . obtusissimum. Los caracteres diferenciales son: estomas paracíticos en ambas epidermis, índice estomático en epidermis adaxial (5,71)-6,62-(8,33) y en epidermis abaxial (6,45)-1 1,20-(14,29); presencia de drusas en todo el mesófilo. Se presentan así elementos de diagnóstico útiles a la hora de identificar a la especie estudiada. Palabras clave: Phoradendron obtusissimum, morfoanatomía, planta medicinal.

Alteraciones anatómicas en epidermis de hojas infectadas de Phoradendron bathyoryctum Eichler (Viscaceae) / Anatomical alterations in epidermis of infected leaves of Phoradendron bathyoryctum Eichler (Viscaceae)

Phoradendron bathyoryctum Eichler (Viscaceae) es una planta hemiparásita que crece en la República Argentina sobre varias especies arbóreas. Se utiliza en medicina popular de la misma manera que el muérdago europeo (Viscum album L. ­Viscaceae­), para disminuir la presión arterial. Los muérdagos, a veces, pueden ser susceptibles de epiparasitismo, o también sufrir el ataque de diferentes agentes fitopatógenos. El objetivo de este estudio es analizar los cambios anatómicos que se producen en las hojas de Ph. bathyoryctum cuando son afectadas por algún agente infeccioso. Se colectaron ejemplares sanos e infectados, los últimos, con lesiones foliares superficiales. Se realizaron técnicas de raspado, diafanizado y obtención de epidermis en las hojas de los ejemplares. También se practicaron reacciones histoquímicas. En las hojas infectadas se observó una destrucción progresiva de los estomas y cambios en el resto de los tejidos epidérmico y subepidérmico, que dieron como resultado la formación de estructuras visibles macroscópicamente, y semejantes a lenticelas foliares. De acuerdo con las observaciones realizadas y por comparación con la bibliografía consultada, se supone que el daño foliar se inicia en el estoma donde se producen cambios estructurales hasta su destrucción, la modificación de las células adyacentes y la formación de lesiones superficiales en las hojas infectadas. En cuanto al agente, si bien no se pudo determinar en esta oportunidad, podría asociarse a algún tipo de virus. Se sugiere realizar futuros estudios para confirmar si los virus son los causantes de las lesiones. (AU)

Impacts of dwarf mistletoe on the physiology of host Tsuga heterophylla trees as recorded in tree-ring C and O stable isotopes.

Dwarf mistletoes, obligate, parasitic plants with diminutive aerial shoots, have long-term effects on host tree water relations, hydraulic architecture and photosynthetic gas exchange and can eventually induce tree death. To investigate the long-term (1886-2010) impacts of dwarf mistletoe on the growth and gas exchange characteristics of host western hemlock, we compared the diameter growth and tree-ring cellulose stable carbon (C) and oxygen (O) isotope ratios (δ(13)Ccell, δ(18)Ocell) of heavily infected and uninfected trees. The relative basal area growth of infected trees was significantly greater than that of uninfected trees in 1886-90, but declined more rapidly in infected than uninfected trees through time and became significantly lower in infected than uninfected trees in 2006-10. Infected trees had significantly lower δ(13)Ccell and δ(18)Ocell than uninfected trees. Differences in δ(18)Ocell between infected and uninfected trees were unexpected given that stomatal conductance and environmental variables that were expected to influence the δ(18)O values of leaf water were similar for both groups. However, estimates of mesophyll conductance (gm) were significantly lower and estimates of effective path length for water movement (L) were significantly higher in leaves of infected trees, consistent with their lower values of δ(18)Ocell. This study reconstructs the long-term physiological responses of western hemlock to dwarf mistletoe infection. The long-term diameter growth and δ(13)Ccell trajectories suggested that infected trees were growing faster than uninfected trees prior to becoming infected and subsequently declined in growth and leaf-level photosynthetic capacity compared with uninfected trees as the dwarf mistletoe infection became severe. This study further points to limitations of the dual-isotope approach for identifying sources of variation in δ(13)Ccell and indicates that changes in leaf internal properties such as gm and L that affect δ(18)Ocell must be considered.

An antibody against a conserved C-terminal consensus motif from plant alternative oxidase (AOX) isoforms 1 and 2 label plastids in the explosive dwarf mistletoe (Arceuthobium americanum, Santalaceae) fruit exocarp.

Dwarf mistletoes, genus Arceuthobium (Santalaceae), are parasitic angiosperms that spread their seeds by an explosive process. As gentle heating triggers discharge in the lab, we wondered if thermogenesis (endogenous heat production) is associated with dispersal. Thermogenesis occurs in many plants and is enabled by mitochondrial alternative oxidase (AOX) activity. The purpose of this study was to probe Arceuthobium americanum fruit (including seed tissues) collected over a 10-week period with an anti-AOX antibody/gold-labeled secondary antibody to determine if AOX could be localized in situ, and if so, quantitatively assess whether label distribution changed during development; immunochemical results were evaluated with Western blotting. No label could be detected in the mitochondria of any fruit or seed tissue, but was observed in fruit exocarp plastids of samples collected in the last 2 weeks of study; plastids collected in week 10 had significantly more label than week 9 (p = 0.002). Western blotting of whole fruit and mitochondrial proteins revealed a signal at 30-36 kD, suggestive of AOX, while blots of whole fruit (but not mitochondrial fraction) proteins showed a second band at 40-45 kD, in agreement with plastid terminal oxidases (PTOXs). AOX enzymes are likely present in the A. americanum fruit, even though they were not labeled in mitochondria. The results strongly indicate that the anti-AOX antibody was labeling PTOX in plastids, probably at a C-terminal region conserved in both enzymes. PTOX in plastids may be involved in fruit ripening, although a role for PTOX in thermogenesis cannot be eliminated.

Impact of eastern dwarf mistletoe (Arceuthobium pusillum) on host white spruce (Picea glauca) development, growth and performance across multiple scales.

Infection by eastern dwarf mistletoe (Arceuthobium pusillum) modifies needle and branch morphology and hastens white spruce (Picea glauca) mortality. We examined potential causal mechanisms and assessed the impacts of infection-induced alterations to host development and performance across scales ranging from needle hormone contents to bole expansion. Needles on infected branches (IBs) possessed higher total cytokinin (CK) and lower abscisic acid contents than needles on uninfected branches (UBs). IBs exhibited greater xylem growth than same-aged UBs, which is consistent with the promotive effect of CKs on vascular differentiation and organ sink strength. Elevated CK content may also explain the dense secondary and tertiary branching observed at the site of infection, i.e. the formation of 'witches' brooms' with significantly lower light capture efficiencies. Observed hormone perturbations were consistent with higher rates of transpiration, lower water use efficiencies (WUEs) and more negative needle carbon isotope ratios observed for IBs. Observed reductions in needle size allowed IBs to compensate for reduced hydraulic conductivity. Severe infections resulted in dramatically decreased diameter growth of the bole. It seems likely that the modifications to host hormone contents by eastern dwarf mistletoe infection led white spruce trees to dedicate a disproportionate fraction of their photoassimilate and other resources to self-shaded branches with low WUE. This would have decreased the potential for fixed carbon accumulation, generating a decline in the whole-tree resource pool. As mistletoe infections grew in size and the number of IBs increased, this burden was manifested as increasingly greater reductions in bole growth.