Aerial and terrestrial root habits influence the composition of the cell walls of Vanilla phaeantha (Orchidaceae).

In response to the restrictions imposed by their epiphytic habit, orchids have developed structural traits that allow greater efficiency in water uptake and use, such as a complex adventitious root system with velamen. The composition of cell wall of this specialized epidermis can be altered according to the substrate to which it is fixed, influencing wall permeability, absorption, and storage of water in roots. The current study aimed to evaluate the cell wall composition of adventitious roots of Vanilla phaeantha (Orchidaceae) that grow attached to the phorophyte, fixed in the soil, or hung free. Immunocytochemical analyses were used to determine the protein, hemicellulose, and pectin composition of the cell walls of aerial and terrestrial roots. We observed that pectins are present in the different tissues of the aerial roots, while in the terrestrial roots, they are concentrated in the cortical parenchyma. The deposition of xyloglucans, extensins, and arabinogalactans was greater in the epidermis of the free side of the roots attached to the phorophyte. The strong labeling of pectins in aerial roots may be related to the influx of water and nutrients, which are generally scarce in this environment. The arrangement of hemicelluloses and proteins with the pectins may be associated with increased cell rigidity and sustainability, a feature of interest for the aerial roots. In summary, the habit of roots can interfere with the non-cellulosic composition of the cell walls of V. phaeantha, possibly related to changes in cell functionality.

Effect of seasonality on the leaf phenology and physiology of Byrsonima species (Malpighiaceae)

Introduction: Defined seasonality in savanna species can stimulate physiological responses that maximize photosynthetic metabolism and productivity. However, those physiological responses are also linked to the phenological status of the whole plant, including leaf phenophases. Objective: To study how physiological traits influence phenophase timing among congeneric and co-occurring savanna species. Methods: We evaluated the leaf phenology and physiological traits of populations of Byrsonima intermedia, B. coccolobifolia, and B. verbascifolia. Physiological measurements were performed at the onset of the dry and rainy seasons and again late in the season. Results: B. intermedia and B. coccolobifolia were classified as brevideciduous and B. verbascifolia as evergreen. The maximum quantum yield for B. intermedia and B. coccolobifolia were lowest during the dry season. At the onset of the dry period, the highest chloroplastidic pigment levels were observed, which decreased as the season advanced, total chlorophyll/carotenoid ratios were lowest, and carotenoid contents were highest. We detected low starch content values at the start of the rainy season, coinciding with the resumption of plant growth. Two months into this season, the leaves were at their peak structural and functional maturity, with high water-soluble polysaccharide values and photosynthetic rates, and were storing large amounts of starch. Conclusions: Physiological and leaf phenological strategies of the Byrsonima species were related to drought resistance and acclimatization to the seasonality of savanna water resources. The oscillations of the parameters quantified during the year indicated a strong relationship with water seasonality and with the phenological status of the leaves.

Introducción: La marcada estacionalidad en las especies de sabana puede estimular respuestas fisiológicas que maximicen el metabolismo fotosintético y la productividad. Sin embargo, esas respuestas fisiológicas están vinculadas al estado fenológico de toda la planta, incluidas las fenofases de las hojas. Objetivo: Estudiar cómo los rasgos fisiológicos influyen en el tiempo de la fenofase entre especies de sabana congenéricas y concurrentes. Métodos: Evaluamos la fenología y características fisiológicas de poblaciones de Byrsonima intermedia, B. coccolobifolia y B. verbascifolia. Las mediciones fisiológicas se realizaron al inicio de la estación seca y lluviosa, y de nuevo al final de la estación. Resultados: B. intermedia y B. coccolobifolia se clasificaron como brevicaducifolias y B. verbascifolia como perennifolias. El rendimiento cuántico máximo para B. intermedia y B. coccolobifolia fueron más bajos durante la época seca. Al inicio del período seco, se observaron niveles de pigmentos cloroplastídicos más altos, aunque los niveles de clorofila disminuyeron a medida que avanzaba la estación seca, las proporciones clorofila/carotenoides totales fueron más bajas y los contenidos de carotenoides más altos. Detectamos valores bajos de contenido de almidón al inicio de la época lluviosa, que coincide con la reanudación del crecimiento de la planta. A dos meses de esta época, las hojas estaban en su máxima madurez estructural y funcional, con altos valores de polisacáridos solubles en agua y tasas fotosintéticas, y almacenaban grandes cantidades de almidón. Conclusiones: Las estrategias fisiológicas y fenológicas de las hojas de las especies de Byrsonima estaban relacionadas con la resistencia a la sequía y la aclimatación a la estacionalidad de los recursos hídricos de la sabana. Las oscilaciones de los parámetros cuantificados durante el año indicaron una fuerte relación con la estacionalidad hídrica y con los estados fenológicos de las hojas.

Structural plasticity in roots of the hemiepiphyte Vanilla phaeantha Rchb.f. (Orchidaceae): a relationship between environment and function.

The aerial environment appears to structurally modify roots, which frequently show specializations for absorbing water and nutrients. Among those specializations are the velamen, a multiseriate epidermis generally composed of dead mature cells, and greater degrees of lignification in the endodermis, exodermis, and pith. Vanilla phaeantha is a hemiepiphyte used here as a model of study to determine which root characteristics demonstrate the most plasticity in response to aerial and terrestrial environments. It produces roots growing under three conditions: (1) aerial and free, growing from the highest branches towards the ground; (2) aerial roots attached to the phorophyte; and (3) terrestrial. Samples taken 3 cm from the apices were used to prepare histological slides. The tissues and other anatomical structures were measured and histochemically characterized. The most plastic characteristics were the external periclinal thicknesses of the exodermis and the total area occupied by the aerenchyma lacunae. The free roots were the longest, did not evidence root hairs, and had the largest number of the aerenchyma lacunae; they also evidenced greater thicknesses of the exodermis in contact with the epidermis walls that helped maintain their shapes. Terrestrial roots had root hairs around the entire circumference and intense infestations of mycorrhiza, indicating their involvement in nutrient acquisition. The adhering roots evidenced free regions similar to those of aerial roots, as well as adhering regions showed characteristics similar to terrestrial roots (with root hairs and mycorrhiza infestations).

Pseudophacopteron longicaudatum (Hemiptera) induces intralaminar leaf galls on Aspidosperma tomentosum (Apocynaceae): a qualitative and quantitative structural overview.

The structural complexity of galls depends on species-specific interaction driven by the galling taxa. However, the host plant and environment stressors can impose limits on gall developmental patterns and impact the establishment of gall morphology. Herein, we employed qualitative and quantitative approaches in order to elucidate how cell divisions, elongation patterns, and tissue organization are determinant for the development of intralaminar gall morphology induced by Pseudophacopteron longicaudatum Malenovský, Burckhardt, Queiroz, Isaias & Oliveira (Hemiptera: Psylloidea: Phacopteronidae) on leaves of Aspidosperma tomentosum Mart. (Apocynaceae). In addition, we aimed to determine which anatomical process can discriminate the stages of gall development, plus, examine the histochemical and cytological profiles of the galls. The differentiated structures, mainly abaxial epidermis and spongy parenchyma, are associated with gall closure, with hyperplastic events concentrated in the young phase of the galls. Thus, epidermis and spongy parenchyma hypertrophy and are responsible for the determination of the nymphal chamber formation and gall shape. The mature galls do not differentiate into a typical nutritive cells and do not develop a histochemical gradient in their tissues. The cytological features of galls such as plastoglobules and multivesicular bodies are related to ROS scavenging mechanisms due the high oxidative stress.

Chemical composition of cell walls in velamentous roots of epiphytic Orchidaceae.

The chemical composition of the cell walls strongly affects water permeability and storage in root tissues. Since epiphytic orchids live in a habitat with a highly fluctuating water supply, the root cell walls are functionally important. In the present study, we used histochemistry and immunocytochemistry techniques in order to determine the composition of the cell walls of root tissues of 18 epiphytic species belonging to seven subtribes across the Orchidaceae. The impregnation of lignin in the velamen cells reinforces its function as mechanical support and can facilitate apoplastic flow. Pectins, as well cellulose and lignins, are also essential for the stability and mechanical support of velamen cells. The exodermis and endodermis possess a suberinized lamella and often lignified walls that function as selective barriers to apoplastic flow. Various cortical parenchyma secondary wall thickenings, including phi, reticulated, and uniform, prevent the cortex from collapsing during periods of desiccation. The presence of highly methyl-esterified pectins in the cortical parenchyma facilitates the formation of gels, causing wall loosening and increased porosity, which contributes to water storage and solute transport between cells. Finally, cells with lipid or lignin impregnation in the cortical parenchyma could increase the water flow towards the stele.

Structural, histochemical and photosynthetic profiles of galls induced by Eugeniamyia dispar (Diptera: Cecidomyiidae) on the leaves of Eugenia uniflora (Myrtaceae) / Perfiles estructurales, histoquímicos y fotosintéticos de las agallas inducidas por Eugeniamyia dispar (Diptera: Cecidomyiidae) en las hojas de Eugenia uniflora (Myrtaceae)

Abstract Gall-inducing insects manipulate the structural, histochemical and physiological profiles of host-plant tissues to develop galls. We evaluated galls induced by Eugeniamyia dispar on the leaves of Eugenia uniflora in an attempt to answer the following questions: (i) How does this gall-inducing insect change the structural and histochemical profiles of the host-plant organ? (ii) Despite structural changes, can gall tissues maintain photosynthetic activity? Starch, proteins, reducing sugars and reactive oxygen species were detected mainly in the nutritive tissue surrounding the larval chamber. Despite structural changes, the galls induced by E. dispar on E. uniflora retain chlorophyllous tissue, although its amount and photosynthetic activity are less than that of non-galled leaves. This reduced photosynthetic activity, in association with the presence of large intercellular spaces, could improve gas diffusion and, consequently, avoid hypoxia and hypercarbia in gall tissue.(AU)

Resumen Los insectos que inducen las agallas manipulan los perfiles estructurales, histoquímicos y fisiológicos de los tejidos de la planta hospedera para su desarrollo. Nosotros evaluamos las agallas inducidas por Eugeniamyia dispar en las hojas de Eugenia uniflora en un intento de responder las siguientes preguntas: (i) ¿Cómo este insecto inductor de agallas cambia los perfiles estructurales e histoquímicos en el órgano de la planta hospedera? (ii) A pesar de las modificaciones estructurales, ¿pueden los tejidos de la agalla mantener la actividad fotosintética? El almidón, las proteínas, los azúcares reductores y las especies reactivas de oxígeno se detectaron principalmente en la capa de tejido nutritivo que rodea a la cavidad larval. A pesar de las modificaciones estructurales, las agallas inducidas por E. dispar en E. uniflora retienen su tejido clorofílico, aunque su cantidad y actividad fotosintética son menores que en las hojas no agalladas. Esta actividad fotosintética reducida, asociado a la presencia de grandes espacios intercelulares, pueden mejorar la difusión de gases y, en consecuencia, evitar la hipoxia y la hipercapnia en los tejidos de las agallas.(AU)

Sink Status and Photosynthetic Rate of the Leaflet Galls Induced by Bystracoccus mataybae (Eriococcidae) on Matayba guianensis (Sapindaceae).

The galling insect Bystracoccus mataybae (Eriococcidae) induces green and intralaminar galls on leaflets of Matayba guianensis (Sapindaceae), and promotes a high oxidative stress in host plant tissues. This biotic stress is assumed by the histochemical detection of hydrogen peroxide, a reactive oxygen species (ROS), whose production alters gall physiology. Thus, we hypothesize that high levels of nutrients are accumulated during gall development in response to a local maintenance of photosynthesis and to the galling insect activity. Moreover, the maintenance of low levels of photosynthesis may guarantee O2 production and CO2 consumption, as well as may avoid hypoxia and hypercarbia in gall tissues. To access the photosynthesis performance, the distribution of chlorophyllous tissues and the photochemical and carboxylation rates in gall tissues were analyzed. In addition, histochemical tests for hydrogen peroxide and phenolic derivatives were performed to confirm the biotic stress, and set the possible sites where stress dissipation occurs. The contents of sugars and nitrogen were evaluated to quantify the gall sink. Currently, we assume that the homeostasis in gall tissues is ruptured by the oxidative stress promoted by the galling insect activity. Thus, to supply the demands of gall metabolism, the levels of water-soluble polysaccharides and starch increase in gall tissues. The low values of maximum quantum efficiency of PSII (Fv/Fm) indicate a low photosynthetic performance in gall tissues. In addition, the decrease of PSII operating efficiency, (F'm-F')/F'm, and Rfd (instantaneous fluorescence decline ratio in light, to measure tissue vitality) demonstrate that the tissues of B. mataybae galls are more susceptible to damage caused by stressors than the non-galled tissues. Thus, the high oxidative stress in gall developmental sites is dissipated not only by the accumulation of phenolic derivatives in the protoplast, but also of lignins in the walls of neoformed sclereids.

The imbalance of redox homeostasis in arthropod-induced plant galls: Mechanisms of stress generation and dissipation.

BACKGROUND: Galls have specialized tissues for the protection and nutrition of the inducers, and these tissues have been studied from the developmental and histochemical perspectives. Recently, the role of oxidative stress in galls has been tested histochemically through detection of H2O2 in gall tissues. SCOPE OF REVIEW: Developmental processes and cytological events are revisited from the perspective of the redox-potential balance in both the apoplast and symplast, especially concerning the accumulation of reactive oxygen species (ROS). MAJOR CONCLUSIONS: The redox potential is imbalanced differently in the apoplast and symplast at gall sites, with the apoplast having lower antioxidant-buffering capacity than the symplast. The strategies to recover redox-potential homeostasis involve the dissipation of ROS by scavenging molecules, such as phenolics, flavonoid derivatives, tocopherol, and enzyme systems. GENERAL SIGNIFICANCE: Insect galls are good models to test developmental hypotheses. Although the exact mechanisms of gall induction and development have not been elucidated at the biochemical and biophysical levels, modulation of the redox potential is involved in the crucial steps of gall initiation and establishment. This article is part of a Special Issue entitled Redox regulation of differentiation and de-differentiation.

Desempenho fotossintético de folhas jovens e maduras de Vochysia cinnamomea (Vochysiaceae) em áreas de cerrado rupestre intactas e pós-queimada / Photosynthetic performance of young and mature leaves of Vochysia cinnamomea (Vochysiaceae) at intact and after fire areas of cerrado rupestre

O fogo exerce um papel importante como modelador dos ecossistemas de diversas formações vegetais, especialmente o Cerrado. Sua ação induz a brotação em diversas espécies, muitas vezes formando folhas mais vigorosas e fisiologicamente mais ativas. Nesse contexto, o presente trabalho investigou o desempenho fotossintético de folhas jovens e maduras de Vochysia cinnamomea Pohl (Vochysiaceae) em resposta à ação do fogo natural sobre uma área de cerrado rupestre da Serra da Canastra, Minas Gerais, comparando-se; (1) folhas jovens de área queimada e não queimada e (2) folhas jovens e maduras de um mesmo indivíduo. Foram analisadas folhas maduras de indivíduos de área não queimada cuja brotação ocorreu anterior à queimada, e folhas jovens de indivíduos de áreas queimadas e não queimadas cuja brotação ocorreu após a passagem do fogo. Foram coletados e analisados dados relativos às taxas fotossintéticas, rendimento quântico potencial e efetivo, taxa relativa de transporte de elétrons, assimilação líquida de CO2, condutância estomática, transpiração e teores de clorofila. Não houve diferenças significativas entre as folhas jovens da área queimada e da área não queimada em relação aos processos fisiológicos testados. Desta forma não há nenhum tipo de resposta rápida em relação à passagem do fogo. Entretanto, foram encontradas diferenças significativas quando comparadas folhas jovens e maduras. É fato que folhas jovens de V. cinnamomea são estruturalmente distintas de folhas maduras, são mais suculentas e pilosas enquanto as folhas maduras são mais coriáceas, glabras e com cutícula evidente. Estas diferenças estruturais e os estágios fisiológicos de maturação distintos se refletem nas características fisiológicas estudadas nestas folhas que, quando maduras apresentam-se com menor grau de fotoinibição, maior teor de clorofilas e maior assimilação líquida de CO2.

Post-fire effect plays an important role as a modulator of plant ecosystems, especially of the Cerrado. It induces leaf sprouting in several species, often forming vigorous and more physiologically active leaves. In the present study it was investigated the photosynthetic performance of young and mature leaves of Vochysia cinnamomea Pohl (Vochysiaceae) in response to the fire action in a "cerrado rupestre" area of Serra da Canasta, Minas Gerais, comparing; (1) young leaves from fired and intact area, and (2) young and mature leaves from the same plant. Mature leaves from intact area plants which leaf sprouting occurred before fire action in the adjacent area, and young leaves from intact and fired area which leaf sprouting occurred after fire action were analyzed. Data were collected and analyzed on photosynthetic rates, potential and effective quantum yield, electron transport rate, CO2 assimilation, stomatal conductance, transpiration and chlorophyll contents. There were no significant differences between the young leaves of the burned and unburned area in relation to physiological parameters tested. Thus there is no kind of quick response in relation to fire effects. However, significant differences between young and mature leaves were found. Young leaves are structurally distinct of the mature leaves, been more succulent and pilous while mature leaves are more coriaceous, glabrous and with thicked cuticle. The structural differences between young and mature leaves are reflected in distinct physiological performance. Mature leaves present lower degree of photoinhibition, higher pigment content and CO2 assimilation.

Nitric oxide increases tolerance responses to moderate water deficit in leaves of Phaseolus vulgaris and Vigna unguiculata bean species.

Drought stress is one of the most intensively studied and widespread constraints, and nitric oxide (NO) is a key signaling molecule involved in the mediation of abiotic stresses in plants. We demonstrated that a sprayed solution of NO from donor sodium nitroprusside increased drought stress tolerance responses in both sensitive (Phaseolus vulgaris) and tolerant (Vigna unguiculata) beans. In intact plants subjected to halting irrigation, NO increased the leaf relative water content and stomatal conductance in both species. After cutting leaf discs and washing them, NO induced increased electrolyte leakage, which was more evident in the tolerant species. These leaf discs were then subjected to different water deficits, simulating moderate and severe drought stress conditions through polyethylene glycol solutions. NO supplied at moderate drought stress revealed a reduced membrane injury index in sensitive species. In hydrated discs and at this level of water deficit, NO increased the electron transport rate in both species, and a reduction of these rates was observed at severe stress levels. Taken together, it can be shown that NO has an effective role in ameliorating drought stress effects, activating tolerance responses at moderate water deficit levels and in both bean species which present differential drought tolerance.

Burkholderia dolosa phenotypic variation during the decline in lung function of a cystic fibrosis patient during 5.5 years of chronic colonization.

Although rarely isolated from cystic fibrosis (CF) patients, Burkholderia dolosa is associated with accelerated lung function decline. During 18 years of epidemiological surveillance in the major Portuguese CF centre in Lisbon, only one patient was infected with B. dolosa. Pulmonary deterioration, associated with the evolution of forced expiratory volume in 1 s, occurred during 5.5 years of colonization with this B. dolosa clone (with the new sequence type ST-668). Transient co-colonization with Burkholderia cenocepacia and other bacterial and fungal pathogens occurred, but B. dolosa prevailed until the patient's death. The systematic assessment of relevant phenotypes for the sequential clonal isolates examined in this retrospective study (14 of B. dolosa and four of B. cenocepacia) showed that they were variants, although in general no isolation time-dependent pattern of alteration was identified. However, the first B. dolosa isolate retrieved was more susceptible to gentamicin, imipenem and tobramycin, and exhibited a higher swarming motility compared with most of the isolates obtained during the later stages of disease progression and antimicrobial therapy.

Synchronism between Aspidosperma macrocarpon Apocynaceae resources allocation and the establishment of the gall inducer Pseudophacopteron sp. Hemiptera: Psylloidea / Sincronismo de Aspidosperma macrocarpon Apocynaceae entre la asignación de recursos y el establecimiento del inductor de agallas Pseudophacopteron sp. Hemiptera: Psylloidea

The joint interpretation of phenology and nutritional metabolism provides important data on plant tissues reactivity and the period of gall induction. A population of Aspidosperma macrocarpon Apocynaceae with leaf galls induced by a Pseudophacopteron sp. Psylloidea was studied in Goiás state, Brazil. Assuming the morphological similarity between host leaves and intralaminar galls, a gradient from non-galled leaves towards galls should be generated, establishing a morpho-physiological continuum. The phenology, infestation of galls, and the carbohydrate and nitrogen contents were monthly evaluated in 10-20 individuals, from September 2009 to September 2010. Our objective was to analyze the nutritional status and the establishment of a physiological continuum between the galls and the non-galled leaves of A. macrocarpon. The period of leaf flushing coincided with the highest levels of nitrogen allocated to the new leaves, and to the lowest levels of carbohydrates. The nutrients were previously consumed by the growing leaves, by the time of gall induction. The levels of carbohydrates were higher in galls than in non-galled leaves in time-based analyses, which indicateed their potential sink functionality. The leaves were infested in October, galls developed along the year, and gall senescence took place from March to September, together with host leaves. This first senescent leaves caused insect mortality. The higher availability of nutrients at the moment of gall induction was demonstrated and seems to be important not only for the establishment of the galling insect but also for the responsiveness of the host plant tissues.

La interpretación conjunta de la fenología y el metabolismo nutricional proporciona datos importantes sobre la reacción de tejidos vegetales y el período de inducción de agallas. En el estado de Goiás, Brasil se estudió una población de Aspidosperma macrocarpon Apocynaceae con agallas foliares inducidas por un Pseudophacopteron sp. Psylloidea. Suponiendo que la similitud morfológica entre las hojas del hospedero y las agallas intralaminares genera un gradiente de hojas sin agallas hacia hojas con agallas, se establece un continuo morfo-fisiológico. La fenología, la infestación de las agallas y el contenido de carbohidratos y nitrógeno se evaluaron mensualmente en 10-20 individuos, de septiembre 2009 a septiembre 2010. El objetivo fue analizar el estado nutricional y el establecimiento de un continuo fisiológico entre las hojas que producen agallas y las hojas sin agallas de A. macrocarpon. El período de emergencia de hojas coincidió con los niveles más altos de nitrógeno en las hojas nuevas, y los niveles más bajos de carbohidratos.Los nutrientes se consumieron previamente por las hojas en crecimiento, en el momento de inducción de las agallas. Los niveles de carbohidratos fueron más altos en las hojas con agallas que en aquellas sin agallas, en análisis basados en tiempo, lo que indica su ciclo de funcionalidad potencial. Las hojas hospederas se infestaron en octubre, el desarrollo y la senescencia de las agallas se llevó a cabo entre marzo y septiembre, en las hojas hospederas. Estas primeras hojas senescentes causaron mortalidad de insectos. Hay mayor disponibilidad de nutrientes en el momento de la inducción de las agallas y parece ser importante no sólo para el establecimiento del insecto que produce agallas, sino también para la capacidad de respuesta de los tejidos de la planta hospedera.

Structural adaptations of two sympatric epiphytic orchids (Orchidaceae) to a cloudy forest environment in rocky outcrops of Southeast Brazil.

The survival of plants in epiphytic environments depends on vegetative adaptations capable to defraud different stresses. Based on the structural diversity of the Orchidaceae, the current study has the objective of relating the anatomical structure of Dichaea cogniauxiana and Epidendrum secundum with the distinct environments where they live. It was expected that, despite structural similarities as strategies for resource acquisition, some peculiar variations related to the distinct light microenvironments (inside or in the edge of the nebular forest, near to "campo rupestre" area) might be found. Leaves and roots of both species were collected in a nebular forest located at a "campo rupestre" area at Serra da Piedade, Brazil), in January and February 2005. D. cogniauxiana is adhered to trunks, in sites with high atmospheric humidity and shaded, while E. secundum is located at the edge of the nebular forest, in more luminous sites. The leaves of E. secundum had thicker cuticle and higher number of stomata per area than those of D. cogniauxiana, characteristics coherent with their distinct pattern of exhibition to sun light. The suprastomatic chambers formed by the thicker cuticle may function as a barrier of resistance to water evaporation. The succulence of the leaves of E. secundum propitiates organic acids storage at night, and the storage of starch may be involved in PEP-carboxylase metabolism, both propitiating CAM mechanism. Roots with larger number of cell layers of the velamen, and specialized thick walled cortical cells (both in E. secundum) help water absorption and indicate better adaptation to an environment with intense solar radiation and a probable higher water deficit. The remarkable cell wall thickening of E. secundum exodermis can confer more efficient protection against the excess of transpiration at the border of the nebular forest. On the other hand, besides D. cogniauxiana be epiphyte, it is in a low position - in a shaded environment and with high relative humidity. Its thin thickened velamen permits the entrance of the low available light, and photosynthesis, producing oxygen and helping to avoid hypoxia condition. As features registered for D. cogniauxiana and E. secundum roots, we can depict the velamen, distinct exodermis and endodermis, and specialized thick walled cortical cells as characteristic of epiphytic plants.

Synchronism between Aspidosperma macrocarpon (Apocynaceae) resources allocation and the establishment of the gall inducer Pseudophacopteron sp. (Hemiptera: Psylloidea).

The joint interpretation of phenology and nutritional metabolism provides important data on plant tissues reactivity and the period of gall induction. A population of Aspidosperma macrocarpon (Apocynaceae) with leaf galls induced by a Pseudophacopteron sp. (Psylloidea) was studied in Goiás state, Brazil. Assuming the morphological similarity between host leaves and intralaminar galls, a gradient from non-galled leaves towards galls should be generated, establishing a morpho-physiological continuum. The phenology, infestation of galls, and the carbohydrate and nitrogen contents were monthly evaluated in 10-20 individuals, from September 2009 to September 2010. Our objective was to analyze the nutritional status and the establishment of a physiological continuum between the galls and the non-galled leaves of A. macrocarpon. The period of leaf flushing coincided with the highest levels of nitrogen allocated to the new leaves, and to the lowest levels of carbohydrates. The nutrients were previously consumed by the growing leaves, by the time of gall induction. The levels of carbohydrates were higher in galls than in non-galled leaves in time-based analyses, which indicateed their potential sink functionality. The leaves were infested in October, galls developed along the year, and gall senescence took place from March to September, together with host leaves. This first senescent leaves caused insect mortality. The higher availability of nutrients at the moment of gall induction was demonstrated and seems to be important not only for the establishment of the galling insect but also for the responsiveness of the host plant tissues.

Is the oxidative stress caused by Aspidosperma spp. galls capable of altering leaf photosynthesis?

The generation of ROS (reactive oxygen species) in plant galls may induce the degradation of the membrane systems of a plant cell and increase the number of plastoglobules. This numerical increase has been related to the prevention of damage to the thylakoid systems, and to the maintenance of photosynthesis rates. To investigate this hypothesis in gall systems, a comparative study of the ultrastructure of chloroplasts in non-galled leaves and in leaf galls of A. australe and A. spruceanum was conducted. Also, the pigment composition and the photosynthetic performance as estimated by chlorophyll fluorescence measurements were evaluated. The ultrastructural analyses revealed an increase in the number and size of plastoglobules in galls of both species studied. The levels of total chlorophylls and carotenoids were lower in galls than in non-galled tissues. The chlorophyll a/b ratio did not differ between the non-galled tissues and both kinds of galls. The values of maximum electron transport rate (ETR(MAX)) were similar for all the samples. The occurrence of numerous large plastoglobules in the galled tissues seemed to be related to oxidative stress and to the recovery of the thylakoid membrane systems. The maintenance of the ETR(MAX) values indicated the existence of an efficient strategy to maintain similar photosynthetic rates in galled and non-galled tissues.

Genomic expression analysis reveals strategies of Burkholderia cenocepacia to adapt to cystic fibrosis patients' airways and antimicrobial therapy.

Pulmonary colonization of cystic fibrosis (CF) patients with Burkholderia cenocepacia or other bacteria of the Burkholderia cepacia complex (Bcc) is associated with worse prognosis and increased risk of death. During colonization, the bacteria may evolve under the stressing selection pressures exerted in the CF lung, in particular, those resulting from challenges of the host immune defenses, antimicrobial therapy, nutrient availability and oxygen limitation. Understanding the adaptive mechanisms that promote successful colonization and long-term survival of B. cenocepacia in the CF lung is essential for an improved therapeutic outcome of chronic infections. To get mechanistic insights into these adaptive strategies a transcriptomic analysis, based on DNA microarrays, was explored in this study. The genomic expression levels in two clonal variants isolated during long-term colonization of a CF patient who died from the cepacia syndrome were compared. One of the isolates examined, IST439, is the first B. cenocepacia isolate retrieved from the patient and the other isolate, IST4113, was obtained three years later and is more resistant to different classes of antimicrobials. Approximately 1000 genes were found to be differently expressed in the two clonal variants reflecting a marked reprogramming of genomic expression. The up-regulated genes in IST4113 include those involved in translation, iron uptake (in particular, in ornibactin biosynthesis), efflux of drugs and in adhesion to epithelial lung tissue and to mucin. Alterations related with adaptation to the nutritional environment of the CF lung and to an oxygen-limited environment are also suggested to be a key feature of transcriptional reprogramming occurring during long-term colonization, antibiotic therapy and the progression of the disease.

Comparative anatomy of the absorption roots of terrestrial and epiphytic orchids

The present study compared roots of terrestrial and epiphytic Orchidaceae, analyzing the anatomical characteristics from an ecological point of view. The material was collected at three different sites in Minas Gerais / Brazil and was fixed in FAA. Transverse sections were obtained by freehand sections or from material previously embedded in Paraplast® or Historesin®. The prominent characteristics of the epiphytic group were: significant smaller perimeter, epidermis with 3 or more cell layers, U-thickened exodermal cell walls, O-thickened endodermal cell walls, and a low ratio between the caliber and the number of protoxylem arches. The terrestrial group presented simple or multiseriate epidermis, and exodermis and endodermis with typical Casparian strips. The anatomical characteristics should have evolved with several adaptations to distinct environments during evolutionary process.

O presente trabalho comparou raízes de Orchidaceae epífitas e terrestres, analisando as características sob um ponto de vista ecológico. O material foi coletado em três diferentes regiões de Minas Gerais/Brasil e fixado em FAA. Cortes transversais foram obtidos à mão livre ou em material infiltrado em Paraplast ou Historresina. As principais características do grupo epifítico foram: perímetro significativamente menor, epiderme com 3 ou mais camadas celulares, exoderme com espessamento em U, endoderme com espessamento em O e uma baixa razão entre o calibre e o número de pólos de protoxilema. O grupo terrestre apresentou epiderme simples ou bisseriada e exoderme e endoderme com estrias de Caspary. As características anatômicas podem estar envolvidas com diferentes adaptações aos distintos ambientes durante o processo evolutivo.