Rosy Mary dos Santos Isaias

Species-specific changes in tissue morphogenesis induced by two arthropod leaf gallers in Lantana camara L. (Verbenaceae)

When different cecidogenous species attack the same plant species, each one causes distinct plant tissue reorganisation, and forms typical gall structures. Two Lantana camara L. leaf galls induced by Aceria lantanae (Cook) (Acarina: Eriophyidae) and Schismatodiplosis lantanae (Rubsaamen) (Diptera: Cecidomyiidae) were collected in a subspontaneous population at Rio Grande do Sul, Brazil. A. lantanae crinckle galls were uni- or multi-chambered and contained several mites, caused by several leaf foldings, and consisted of hyperplasic epidermis and parenchyma. S. lantanae induced uni-chambered pouch galls inhabited by one larvae or pupa. This gall consisted predominantly of hypertrophied spongy parenchyma. Our results documented how these herbivores acted in cells with the same initial morphogenetic competence, altering leaf pattern, and inducing their specific extended phenotype.

Illustrated and Annotated Checklist of Brazilian Gall Morphotypes

The analysis on nine inventories on the richness and diversity of galling herbivores in Brazil accounted for 806 gall systems occurring in 443 host-plant species from 74 plant families. This checklist of the Brazilian gall morphotypes proposes seven standardized morphotypes and five additional shapes that group the majority of the three-dimensional shapes reported in literature. Criteria are proposed to standardize the terminology, and a critical analysis is provided aiming to avoid possible inconsistencies in order to generate easily comparable data in future inventories. The morphotypes are herein catalogued in alphabetical order, accompanied by a conceptual definition, an illustration, and examples that best represent the shape. It is proposed that the inventories should present at least the (1) host-plant species, (2) galling herbivore species or its identification to the lowest possible taxonomic level, (3) host-plant galled organ and gall position, (4) gall morphotype, (5) gall color and registration of indumentum when present, (6) gall phenological and developmental data, (7) association with other trophic levels, and (8) additional information, such as dimension, and number of chamber(s).

Do Cecidomyiidae galls of Aspidosperma spruceanum (Apocynaceae) fit the pre-established cytological and histochemical patterns?

Cecidomyiidae galls commonly present a zonation of tissues with lignified cell layers externally limiting a reserve tissue and internally limiting a specialized nutritive tissue next to the larval chamber. The cytological aspects of this specialized tissue indicate high metabolic activity as well as carbohydrate accumulation. In Aspidosperma spruceanum–Cecidomyiidae gall system, ultrastructural and histochemical investigations corroborated this pattern and also revealed the storage of proteins in the nutritive cells. Reactive oxygen species (ROS), callose, and pectin accumulation were related to the feeding activity of the galling herbivore. Phosphorylase, glucose-6-phosphatase, acid phosphatases, invertases, and sucrose synthase activities were detected for the first time, in the Neotropical region, and discussed in relation to gall maintenance and the feeding activity of the Cecidomyiidae.

The influence of light intensity on anatomical structure and pigment contents of Tradescantia pallida (Rose) Hunt. cv. purpurea Boom (Commelinaceae) leaves

The aim of this work was to study the effects of five different light intensities on the anatomical structure and on the pigment contents in leaves of Tradescantia pallida cv. purpurea. Once light intensity became lower, the thickness of leaf lamina and mesophyll were reduced. Adjustments in light-harvesting antenna size were observed: an increase in chlorophyll a + b/carotenoids ratio at low-light growth conditions. There was a strong positive linear correlation between the light intensity values and anthocyanin contents. Hence, T. pallida cv. purpurea acclimation to distinct environmental conditions might be related to its capacity of altering structurally and physiologically its phenotype.

Manipulation of host plant cells and tissues by gall-inducing insects and adaptive strategies used by different feeding guilds

Biologists who study insect-induced plant galls are faced with the overwhelming diversity of plant forms and insect species. A challenge is to find common themes amidst this diversity. We discuss common themes that have emerged from our cytological and histochemical studies of diverse neotropical insect-induced galls. Gall initiation begins with recognition of reactive plant tissues by gall inducers, with subsequent feeding and/or oviposition triggering a cascade of events. Besides, to induce the gall structure insects have to synchronize their life cycle with plant host phenology. We predict that reactive oxygen species (ROS) play a role in gall induction, development and histochemical gradient formation. Controlled levels of ROS mediate the accumulation of (poly)phenols, and phytohormones (such as auxin) at gall sites, which contributes to the new cell developmental pathways and biochemical alterations that lead to gall formation. The classical idea of an insect-induced gall is a chamber lined with a nutritive tissue that is occupied by an insect that directly harvests nutrients from nutritive cells via its mouthparts, which function mechanically and/or as a delivery system for salivary secretions. By studying diverse gall-inducing insects we have discovered that insects with needle-like sucking mouthparts may also induce a nutritive tissue, whose nutrients are indirectly harvested as the gall-inducing insects feeds on adjacent vascular tissues. Activity of carbohydrate-related enzymes across diverse galls corroborates this hypothesis. Our research points to the importance of cytological and histochemical studies for elucidating mechanisms of induced susceptibility and induced resistance.

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.

Reações de defesas químicas e estruturais de Lonchocarpus muehlbergianus Hassl. (Fabaceae) à ação do galhador Euphalerus ostreoides Crawf. (Hemiptera: Psyllidae)

Galhas sao estruturas vegetais induzidas em resposta ao ataque de organismos indutores. Euphalerus ostreoides (Psyllidae) induz galhas sobre a face adaxial de foliolos nas nervuras de segunda ordem de Lonchocarpus muehlbergianus (Fabaceae). Secoes anatomicas foram realizadas e comparados os tecidos de foliolos sadios com os de galhas imaturas e maduras. Testes histoquimicos para deteccao de derivados fenolicos, flavonoides, ligninas, lipidios e amido foram realizados para avaliar o impacto quimico causado pelo galhador. Em termos estruturais, a perda de sinuosidade das celulas epidermicas, a neoformacao de tricomas, de celulas condutoras e de fibras foram os caracteres mais conspicuos observados em decorrencia da inducao das galhas. Destaca-se a hiperplasia e hipetrofia do mesofilo com manutencao da estratificacao, a producao de goticulas lipidicas e amido, flavonas, flavonois e flavanonas nos tecidos das galhas. Contudo, a formacao de cristais de oxonio pela adicao de acido sulfurico somente nos tecidos das galhas foi uma caracteristica marcante. Os resultados sugerem que L. muehlbergianus esta submetida a alto estresse oxidativo induzido pela acao do E. ostreoides. Conclui-se que as alteracoes sao consideradas reacoes de defesa da planta contra herbivoria e mecanismos de adaptacao que em conjunto favorecem o estabelecimento do galhador nos tecidos vegetais.

Cytological and histochemical gradients on two Copaifera langsdorffii Desf. (Fabaceae)—Cecidomyiidae gall systems

Previous ultrastructural and histochemical analysis proposed patterns in the accumulation of substances in galls of Diptera: Cecidomyiidae in some plant species of the temperate region. Similar analyses were done to verify the conservativeness of these patterns in the Neotropical region, where a great number of species of Cecidomyiidae is responsible for a wide diversity of morphotypes. Two gall morphotypes induced by Cecidomyiidae in a unique host plant, Copaifera langsdorffii, were studied. The gradients of carbohydrates and the activity of invertases and acid phosphatases were similar, but the cytological gradients and distribution of proteins evidenced that the sites of the induction as well as the amount of neoformed tissues may be peculiar to each gall system. The production of lipids just in the secretory cavities either in the non-galled or galled tissues indicated a potentiality of the host plant which could not be manipulated by the galling insects. Further, the absence of nucleus in the nutritive tissue, an exclusive feature of the horn-shaped galls, indicates cell death attributed to the feeding habit of the galling herbivore.

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.

Ontogenesis of the leaf and leaf galls induced by Aceria lantanae Cook (Acarina:Eriophyidae) in Lantana camara L. (Verbenaceae)

Aceria lantanae is a phytophagous mite commonly observed inducing galls in Lantana camara leaves. The comparative study of histological and histometric characteristics, during the ontogenesis of leaves and galls, aims to determine which of the healthy tissues morphogenetic events are altered by the galling herbivore. Leaf ontogenetical events of L. camara followed the pattern described in literature. Gall induction causes hyperplasia of epidermis and ground system. At growth and development stage, leaf lamina invagination gives rise to the nymphal chamber, where eriophids reproduce. The cell layer limiting this chamber constitutes the nutritive tissue, where inducers feed, and stimulate cell divisions. At the maturation stage, gall increase in size is followed by an increase in the number of A. lantanae individuals. Gall external covering is characterized by a high density of non-glandular trichomes whose morphotype is particular to the galls. The differentiation of emergencies and neoformation of vascular bundles promotes an increase in the flux of food resources to the inducers. Cell divisions in diverse angles alter the laminar pattern of the leaf firstly related to photosynthesis, and result in verrucous galls which guarantee an adequate microenvironment and nutrition source to A. lantanae colony. At senescent stage, nutritive tissue suberization occurs, indicating the end of the inducers feeding activity. The suberization of nutritive tissue indicates the end of cell cycles, an event that may be related to the death of the deutogyne female, or to the limits imposed by the age of L. camara host leaf.