ABSTRACT Philodendron is the only genus of Araceae in which resin release occurs in the inflorescence. The resinous secretion adheres to the smooth body surface of the pollinating scarab beetles and allows attachment of pollen grains, making its transport possible. In order to understand the process of resin synthesis and release to the external environment, we used structural, ultrastructural and histochemical analyses at different stages of development of the inflorescences of Philodendron adamantinum. Two types of secretory canals were observed in the spathe: small caliber canals near the abaxial face, and larger caliber canals in the adaxial region. Only the latter canals release secretion into the external environment. The secretory epithelium in these canals is formed by a layer of cuneiform cells, and exhibits secretory activity throughout the development of the spathe. Resin exudation is a peculiar characteristic of these canals and appears to result from pressure exerted by the secretory epithelium and by structural modifications in the wall of cells adjacent to the epidermis, which allow the formation of a separation zone whereby the resin is released. The observed synchrony between anther dehiscence and resin exudation of P. adamantinum enhances the role of this secretion in the pollination process.

ABSTRACT In many glandular structures, departure from the cell is only one step in the process of exudate release to the plant surface. Here the set of events that lead nectar to the external environment is presented and discussed mainly for stomata-free nectaries. After being synthesized, the nectar or some of its component needs to be released to the environment where it performs its functions. Nectar precursors derived from cell metabolism need to cross several barriers, such as the cell membrane and cell wall, in order to become nectar. Then the nectar must cross the cuticle or pass through stomata in order to be offered to plant mutualists. Release through stomata is a simple mechanism, but the ways by which nectar crosses the cuticle is still controversial. Hydrophilic pathways in the cuticle and repetitive cycles of rupture or cuticle detachment are the main routes for nectar release in stomata-free nectaries. In addition to nectar, there are other exogenous secretions that must leave the protoplast and reach the plant surface to perform their function. The ways by which nectar is released discussed herein are likely relevant to understanding the release of other hydrophilic products of the secretory process of plants.

Connarus suberosus es una especie típica del bioma Cerrado brasileño, y sus inflorescencias junto con los ramos vegetativos jóvenes están densamente cubiertos por tricomas dendríticas. El objetivo de este estudio es presentar la ocurrencia de un tricoma glandular sin descripción previa para esta especie. La localización, origen y estructura de estos tricomas se observó mediante microscopia óptica, así como electrónica de transmisión y de barrido. Los tricomas glandulares (TGs) se producen en los órganos vegetativos y reproductivos, en sus fases jóvenes. Los TGs consisten en un pedúnculo uniseriado y multicelular, cuyas células contienen compuestos fenólicos, así como un sitio en el cual las células glandulares acumulan compuestos pécticos, almidón y lípidos. La acumulación de aceite en el citosol es impresionante, pues ocupa una gran parte del volumen celular. La porción glandular presenta células con paredes delgadas, un denso citoplasma y un núcleo grande con nucleolo visible. El citoplasma contiene gran cantidad de mitocondrias, plástidos y dictiosomas. El almidón presente en los plástidos se hidroliza durante la fase de síntesis, de tal modo que reduce la densidad del estroma plastidial. Algunos plástidos se fusionan con las vacuolas, además hay pruebas de la conversión de los plástidos en vacuolas. Durante las etapas finales de la actividad de los TGs, se observó un oscurecimiento del protoplasma en algunas de las células glandulares lo que sugiere la existencia de la muerte celular programada; después de lo anterior, los TGs se convierten en caducas. Por lo tanto la aparición de TGs en las superficies expuestas de los órganos en desarrollo en C. suberosus y la naturaleza química de los productos de reserva sugieren que estas estructuras son cuerpos alimenticios. Hay evidencias sobre el papel de estos tricomas en las interacciones planta-hormiga, especialmente en el bioma Cerrado.

Connarus suberosus is a typical species of the Brazilian Cerrado biome, and its inflorescences and young vegetative branches are densely covered by dendritic trichomes. The objective of this study was to report the occurrence of a previously undescribed glandular trichome of this species. The localization, origin and structure of these trichomes were investigated under light, transmission and scanning electron microscopy. Collections were made throughout the year, from five adult specimens of Connarus suberosus near Botucatu, São Paulo, Brazil, including vegetative and reproductive apices, leaves and fruits in different developmental stages, as well as floral buds and flowers at anthesis. Glandular trichomes (GTs) occurred on vegetative and reproductive organs during their juvenile stages. The GTs consisted of a uniseriate, multicellular peduncle, whose cells contain phenolic compounds, as well as a multicellular glandular portion that accumulates lipids. The glandular cell has thin wall, dense cytoplasm (with many mitochondria, plastids and dictyosomes), and a large nucleus with a visible nucleolus. The starch present in the plastids was hydrolyzed during the synthesis phase, reducing the density of the plastid stroma. Some plastids were fused to vacuoles, and some evidence suggested the conversion of plastids into vacuoles. During the final activity stages of the GTs, a darkening of the protoplasm was observed in some of the glandular cells, as a programmed cell death; afterwards, became caducous. The GTs in C. suberosus had a temporal restriction, being limited to the juvenile phase of the organs. Their presence on the exposed surfaces of developing organs and the chemical nature of the reserve products, suggest that these structures are food bodies. Field observations and detailed studies of plant-environment interactions, as well as chemical analysis of the reserve compounds, are still necessary to confirm the role of these GTs as feeding rewards.

El género Hymenaea se caracteriza por una gran diversidad de estructuras secretoras, pero no hay informes de coléteres. El objetivo de este estudio es informar de su existencia en el género, y describir el origen y estructura de los coléteres en Hymenaea stigonocarpa Mart. ex Hayne. Procesamos muestras del ápice de brotes según los métodos generales para microscopio óptico, microscopio electrónico de barrido y microscopio electrónico de transmisión. Los coléteres están predominantemente en la parte adaxial de las estípulas, ocupando la base en una estrecha franja desde la vena media hasta mitad de la longitud de la estípula. En la parte abaxial, se concentran en la base y se restringen a los márgenes. Los coléteres surgen del protoderma; son alargados y en forma de bastoncillo. Sus cuerpos no poseen estratificación; sus células superficiales difieren de las internas solamente por la posición y la presencia de cutícula. Las células de los coléteres poseen paredes delgadas, citoplasma denso, núcleos grandes, muchas mitocondrias, retículo endoplasmático rugoso, y abundantes dictiosomas. Las pruebas histoquímicas con rojo ruteno mostraron compuestos pécticos en el citosol. En H. stigonocarpa, la distribución de los coléteres es compatible con la hipótesis de que protegen el ápice del brote. En esta especie, la protección es reforzada por la envoltura formada por los pares de la estípula.

The genus Hymenaea is characterized by a great diversity of secretory structures, but there are no reports of colleters yet. The objectives of this study are to report the occurrence and describe the origin and structure of colleters in Hymenaea stigonocarpa Mart. ex Hayne. Shoot apex samples were collected, fixed, and processed for light microscopy, scanning electron microscopy, and transmission electron microscopy as per usual methods. Colleters occur predominantly on the stipule’s adaxial side. These structures are found at the base on a narrow strip, corresponding to the median vein up to half the length of the stipule. When present on the abaxial side, they are concentrated at the base and restricted to the margins. Colleters develop from the protoderm; they are elongate and club-shaped. Their body has no stratification; their surface cells differ from the inner cells only in position and presence of cuticle. Colleter cells have thin walls, dense cytoplasm, large nuclei, many mitochondria, rough endoplasmic reticulum, and abundant dictyosomes. Histochemical tests with Ruthenium red showed pectic compounds in the cytosol. In H. stigonocarpa, colleter arrangement is compatible with the hypothesis that they protect shoot apex. In this species, protection is reinforced by the sheath formed by the stipule pairs. Rev. Biol. Trop. 54 (3): 943-950. Epub 2006 Sept. 29.

O jatobá-do-cerrado (Hymenaea stigonocarpa Mart. ex Hayne) apresenta nectários extraflorais (NEFs), os quais são descritos pela primeira vez no gênero. Neste trabalho foram estudadas a distribuição, ontogênese, estrutura e ultra-estrutura dos nectários extraflorais (NEFs). Amostras de folhas em várias fases de desenvolvimento foram coletadas, fixadas e processadas para estudos em microscopia de luz e eletrônica de transmissão e varredura, segundo técnicas convencionais. Testes histoquímicos foram empregados para determinar a natureza química da secreção. Os NEFs estão distribuídos por todo o limbo, sendo mais concentrados nos terços basal e médio de cada folíolo. Estes nectários são embutidos no mesofilo, apresentam tecido secretor envolvido por uma endoderme e são vascularizados por xilema e floema. A atividade secretora dos NEFs é limitada à fase juvenil da folha. Nas folhas mais velhas, os NEFs tornam-se não funcionais. O tecido secretor dos NEFs é formado a partir da protoderme, enquanto a endoderme tem origem no meristema fundamental. No tecido secretor de nectários funcionais as células apresentam citoplasma denso, núcleo volumoso, mitocôndrias, plastídios com sistema de membranas pouco desenvolvido, gotas de óleo dispersas no citosol, dictiossomos e segmentos de retículo endoplasmático liso. A secreção é liberada por meio de rupturas cuticulares e apresenta polissacarídeos e lipídios.

Hymenaea stigonocarpa Mart. ex Hayne, known as "jatobá-do-cerrado" has extrafloral nectaries (EFNs), which are reported for the first time in Hymenaea genus. In this research the origin, distribution, structure, and ultrastructure of the EFNs were studied. Samples of leaflets at different developmental stages were collected, fixed and processed by standard methods for analyses at light and electronic microscopes; histochemical tests were employed to determine the nature of secretion products. EFNs are distributed all over leaf blade, more concentrated on the basal and medial thirds of each leaflet. These nectaries are embedded in the mesophyll, show secretory tissue surrounded by an endodermis, and are vascularized by xylem and phloem. EFN secretory activity was exclusively observed in young leaves. The protoderm origins the EFN secretory tissue, the ground meristem originates the endodermis and the procambium originates the vascular tissues. Secretory cells of functional EFNs showed dense cytoplasm, large nucleus, mitochondria, plastids with a poorly developed membrane system, oil drops scattered in the cytosol, dictyosome, and smooth endoplasmic reticulum segments. Secretion was released by cuticle rupture and contains polysaccharides and lipids.

O objetivo do presente estudo foi avaliar os efeitos da fumagina na anatomia e a atividade fotoquímica em folhas de mogno (Swietenia macrophylla King., Meliaceae). Folhas com e sem fumagina desenvolvidas na sombra foram comparadas com as de folhas de sol, para verificar as diferenças em parâmetros fotoquímicos utilizando-se medidas de fluorescência. As amostras de folhas destinadas a estudos anatômicos foram processadas segundo técnicas convencionais. A intensidade de bloqueio da radiação densidade de fótons fotossinteticamente ativos (DFFA) pela fumagina e seu efeito sobre a atividade fotoquímica foram avaliados. As folhas de sol têm mesofilo espesso e parênquima paliçádico unisseriado enquanto nas folhas de sombra o mesofilo é delgado, independentemente da presença ou não de fumagina. O rendimento quântico efetivo (deltaF/Fm') e a taxa aparente de transporte de elétrons (ETR) das folhas de sol foram superiores às das folhas de sombra. Os valores de ETR sugerem que, nas plantas crescidas na sombra, a saturação da atividade fotoquímica ocorre em menores valores de DFFA. Observaram-se menores valores de deltaF/Fm' nas folhas com fumagina e, conseqüentemente menores valores de ETR. A presença de fumagina promoveu bloqueio de 40% na luz incidente e, conseqüentemente, presume-se um decréscimo adicional nos valores de ETR. Pelos dados, verifica-se que a presença de fumagina não promoveu danos diretos nas folhas, mas reduz a capacidade fotoquímica por diminuir a disponibilidade de luz.

The aim of present study was to evaluate the effects of the sooty mold on anatomy and photochemical activity of mahogany (Swietenia macrophylla) leaves. The photochemical features of shade-developed leaves with or without sooty mold were compared to those of sun leaves using chlorophyll a fluorescence measurements. Leaf anatomy was also evaluated using conventional techniques. The degree of blockage of the photosynthetic active photon flux density (PPFD) by sooty mold and its effect on photochemistry were evaluated. Sun leaves showed thick mesophyll with palisade parenchyma disposed in a uniseriate layer, whereas shade leaves showed narrow mesophyll, independently of sooty mold presence. The effective quantum yield (deltaF/Fm') and the apparent electron transport rate (ETR) of sun leaves were higher than those of shade leaves. The values of ETR suggested that photochemistry saturation occurred at lower PPFD in shade-grown plants. Lower values of the deltaF/Fm' and, consequently, lower values of ETR were observed in leaves with sooty mold. A reduction of 40% of the incident light was seen due to physical blockage by sooty mold which is presumably responsible for an additional decrease of ETR values. Our data indicated that sooty mold did not directly damage the leaf, but reduce leaf photochemistry capacity, by decreasing light availability.

Com o objetivo de estudar a relação entre cristais de oxalato de cálcio e floema, fragmentos de folhas de Peltodon radicans foram fixados e processados, segundo métodos usuais, para estudos ao microscópio de luz e eletrônico de transmissão. Observou-se que os cristais ocorrem nas células da bainha do feixe, lateralmente em relação ao floema. Células intermediárias estabelecem conexão entre elemento crivado e células da bainha, portadoras de cristais, com crescimento intrusivo entre estas. Íons cálcio são abundantes no citoplasma das células da bainha que contém cristais de oxalato de cálcio. Nas células intermediárias a detecção ultra-citoquímica de cálcio também apresentou resultados positivos, enquanto nos elementos crivados a presença deste íon não foi constatada. Há, portanto, um gradiente crescente de concentração de cálcio dos elementos crivados para as células da bainha. Assim, formulamos a hipótese de que a formação de cristais de oxalato de cálcio tem, em P. radicans, o objetivo de controlar os níveis de cálcio citossólico nos elementos crivados.

With the objective of studying the connection between calcium oxalate crystals formation and the phloem, fragments of leaves of Peltodon radicans Pohl (Lamiaceae) were fixed and processed, for light and electron-transmission microscopes. It was observed that the crystals occurred in the cells of the bundle sheath, juxtaposed in relation to the phloem. Intermediary cells established a connection between the sieve element and crystal-bearing sheath cells. Calcium was present abundantly in the cytoplasm of sheath cells as calcium oxalate crystals. The presence of calcium was also detected in the intermediary cells, but in the sieve elements it was not detected. There was, therefore, an increasing concentration gradient of calcium in the sieve elements from sheath cells. Thus, we hypothesized that the formation of calcium oxalate crystals regulates calcium levels in the sieve elements.

As espécies de Tradescantia colonizam uma ampla faixa de ambientes, desde aqueles completamente expostos a luz até aqueles caracteristicamente sombreados. Suas estratégias adaptativas e eficiência como invasoras de culturas estão provavelmente associadas a sua adaptação a intensidades luminosas distintas. Este trabalho mostra os efeitos de cinco diferentes intensidades luminosas na estrutura anatômica e no teor de pigmentos em folhas de Tradescantia pallida. As espessuras da lâmina foliar e do mesofilo foram alteradas, tornando-se mais delgadas à medida que a intensidade luminosa diminuiu. Observou-se um ajuste nos pigmentos fotossintéticos caracterizado por aumentos na razão clorofilas/carotenóides sob condições de baixa intensidade luminosa. Houve uma forte correlação linear positiva entre os valores de intensidade luminosa e teores de antocianinas. Deste modo, pode-se concluir que a aclimatação da espécie aos diferentes habitats está relacionada a alterações estruturais e fotossintéticas.

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.

Nectários extraflorais (NEFs) são estruturalmente variáveis e de ampla ocorrência entre as angiospermas. A ocorrência dos NEFs nas folhas de Pterodon polygalaeflorus Benth. e Pterodon pubescens Benth. (Fabaceae: Papilionoideae) foi detectada em espécimes adultas, durante a produção de novas gemas e flores. Os objetivos deste estudo foram registrar a ocorrência de NEFs em P. pubescens e P. polygalaeflorus, e fornecer dados comparativos sobre a estrutura anatômica destas estruturas. Os NEFs ocorrem na raque e estão localizados sob a inserção de cada peciólulo. Cada nectário consiste de uma pequena elevação cuja porção apical é fortemente invaginada, resultando em uma depressão (o pólo secretor), característica comum a ambas as espécies. Tricomas tectores unicelulares ocorrem ao longo da raque, sendo menos numerosos em P. polygalaeflorus, enquanto em P. pubescens eles cobrem todo o NEF. O tecido secretor consiste de células parenquimáticas com citoplasma denso. O néctar alcança a superfície dos NEFs pela ruptura da fina cutícula que cobre o pólo secretor, uma vez que ambas as espécies não apresentam estômatos ou qualquer outra interrupção da epiderme neste local. A diferença básica entre as duas espécies, em relação aos NEFs, é a densidade da pubescência, que é sempre maior em P. pubescens. Modificações estruturais e de dimensões podem ser observadas até mesmo entre os nectários basais e apicais de uma mesma raque, e portanto tais modificações não apresentam valor taxonômico.

Extrafloral nectaries (EFNs) are structurally variable and widely spread among the angiosperms. The occurrence of EFNs in leaves of Pterodon polygalaeflorus Benth. and Pterodon pubescens Benth. (Fabaceae: Papilionoideae) were detected in adult specimens, at the time of production of new buds and flowers. The goals of the present study are to register the occurrence of the EFNs in P. pubescens and P. polygalaeflorus, and provide comparative data on the anatomical structures. The EFNs occur in the rachis and are located under the insertion of each petiolule. Each nectary consists of a small elevation whose apical portion is deeply invaginated, resulting in a depression (secretory pole), a common characteristic of both species. Unicellular, nonglandular trichomes occur along the rachis, being less numerous in P. polygalaeflorus while in P. pubescens they cover the EFNs. The secretory tissue consists of parenchyma cells with dense cytoplasm compactly arranged. The nectar reaches the surface of the EFNs by rupturing the thin cuticle which covers the secretory pole, since both species lack stomata or any other interruption at the epidermis. The basic difference between the two species, in relation to the EFNs, is the density of the pubescence, which is always greater in P. pubescens. Structural and dimensional modifications may be observed, even between basal and apical nectaries in the same rachis, so it does not constitute a taxonomical tool.