Morphology of the megaspore Lagenoisporites magnus (Chi and Hills 1976) Candilier et al. (1982), from the Carboniferous (lower Mississippian: mid-upper Tournaisian) of Bolivia.

The morphology and structure of megaspores assigned to Lagenoisporites magnus from the Toregua Formation, Retama Group, mid-upper Tournaisian of Bolivia were studied. The analysis was performed with light, fluorescence and scanning electron microscopy. Megaspores were laterally compressed and presented a spherical body with a proximal gula, of the hologula type. Gula had verrucae ornamentation and the spore body presented complex processes consisting of a bulbous base and an internally partitioned projection with sharp apex. In addition to this main ornamentation, perforations were present throughout the spore surface. Megaspores showed well marked curvaturae perfectae due to the abrupt transition existing between the gula ornamentation and the spore body processes. These megaspores were assigned to heterosporous arborescent lycopsids of the Lepidocarpaceae family, as in section view, exospore structure presented a three-dimensional network of fused elements. Likewise, due to a similarity found between sporoderm and Isoetes L. structure, it is evident that megaspores structure has remained intact inside the heterosporous lycopsids. Therefore; the L. magnus structure not only would confirm its affinity with the Lycophyta fossils but also with the living ones.

Cellular and Morpho-histological Foundations of In Vitro Plant Regeneration.

In vitro plant regeneration systems have turned into invaluable tools to plant biotechnology. Despite being poorly understood, the molecular mechanisms underlying the control of both morphogenetic pathways, de novo organogenesis and somatic embryogenesis, have been supported by recent findings involving proteome-, metabolome-, and transcriptome-based profiles. Notwithstanding, the integration of molecular data with structural aspects has been an important strategy of study attempting to elucidate the basis of the cell competence acquisition to further follow commitment and determination to specific a particular in vitro regeneration pathway. In that sense, morpho-histological tools have allowed to recognize cellular markers and patterns of gene expression at cellular level and this way have collaborated in the identification of the cell types with high regenerative capacity. This chapter ties together up those fundamental and important microscopy techniques that help to elucidate that regeneration occurs, most of the time, from epidermis or subepidermal cells and from the procambial cells (pericycle and vascular parenchyma). Important findings are discussed toward ultrastructural differences observed in the nuclear organization among pluripotent and totipotent cells, implying that regeneration occurs from two cellular mechanisms based on cellular reprogramming or reactivation.

Morphology and ultrastructure of megaspores and microspores of Isoetes sehnemii Fuchs (Lycophyta).

The morphology and wall ultrastructure of megaspores and microspores of Isoetes sehnemii that grows in Brazil were analyzed as part of the study of the Isoetaceae present in Southern South America. The observations were performed with light, scanning and transmission electron microscopes. The megaspores are trilete, 350-450microm in equatorial diameter. The surface is reticulate. In section, the sporoderm is 100microm thick including the ornamentation. The wall is composed of a siliceous perispore, which consists of short fused flatten, elements forming a three-dimensional mesh. The exospore has two zones of different structure. The endospore is fibrillar. The microspores are monolete, 21-27microm in equatorial diameter. The sporoderm is composed of a sporopollinic rugulate perispore. A space between the paraexospore and the exospore is evident. The exospore is compact. The endospore is fibrillar. The ultrastructural analysis akes hoologies evident concerning structure and organization of the layers belo the perispore in both spore types. A possible similarity and stability in the ultrustructure of the present spores and fossils could be also inferred. In addition, there would be a correlation among the plant habitat, the spore ornamentation and the geographic distribution.

Isoetes pedersenii, a new species from Southern South America.

The name Isoetes pedersenii H.P. Fuchs (Lycophyta), a species known only from the Mburucuyá National Park, Corrientes, Argentina, is validated. Observations were carried out on herbarium material with stereoscopic, light and scanning electron microscopes. The species is described and typified. A diagnosis and discussion about its distribution and its relationship with the morphology of other species of Isoetes are provided.

Morphology and ultrastructure of megaspores and microspores of Isoetes sehnemii Fuchs (Lycophyta)

The morphology and wall ultrastructure of megaspores and microspores of Isoetes sehnemii that grows in Brazil were analyzed as part of the study of the Isoetaceae present in Southern South America. The observations were performed with light, scanning and transmission electron microscopes. The megaspores are trilete, 350-450μm in equatorial diameter. The surface is reticulate. In section, the sporoderm is 100μm thick including the ornamentation. The wall is composed of a siliceous perispore, which consists of short fused flatten, elements forming a three-dimensional mesh. The exospore has two zones of different structure. The endospore is fibrillar. The microspores are monolete, 21-27μm in equatorial diameter. The sporoderm is composed of a sporopollinic rugulate perispore. A space between the paraexospore and the exospore is evident. The exospore is compact. The endospore is fibrillar. The ultrastructural analysis akes hoologies evident concerning structure and organization of the layers belo the perispore in both spore types. A possible similarity and stability in the ultrustructure of the present spores and fossils could be also inferred. In addition, there would be a correlation among the plant habitat, the spore ornamentation and the geographic distribution.

A morfologia e a ultraestrutura da parede de megasporos e microspores de Isoetes sehnemii que crescem no Brasil foram analisados como parte do estudo de Isoetaceae presente no sul da América do Sul. As observações foram realizadas com microscopias de luz e eletrônicas de transmissão e varredura. Os megasporos são triletes com 350-450μm de diâmetro equatorial. A superfície é reticulada. Em secção o esporoderma possui 100μm de espessura incluindo ornamentação. A parede é composta de um perisporo silicoso que consiste de elementos fusionados curtos e achatados formando uma rede tridimensional. O exosporo tem duas zonas com diferentes estruturas. O endosporo é fibrilar. Os microsporos são monoletes, 21-27μm de diâmetro equatorial. A esporoderme é composta por um perisporo esporopolínico rugulado. Um espaço entre o para-exosporo e o exosporo é evidente. O exosporo é compacto. O endosporo é fibrilar. A análise ultraestrutural torna evidente homologias relativas a estrutura e organização das camadas abaixo do perisporo em ambos os tipos de esporos. Uma possível similaridade e estabilidade na ultraestrutura do presente esporo e fósseis pode também ser inferida. Além disso, haveria uma correlação entre o habitat da planta, a ornamentação do esporo e a distribuição geográfica.

Isoetes pedersenii, a new species from Southern South America

The name Isoetes pedersenii H.P. Fuchs (Lycophyta), a species known only from the Mburucuyá National Park, Corrientes, Argentina, is validated. Observations were carried out on herbarium material with stereoscopic, light and scanning electron microscopes. The species is described and typified. A diagnosis and discussion about its distribution and its relationship with the morphology of other species of Isoetes are provided.

O nome Isoetes pedersenii H.P. Fuchs (Lycophyta) foi validado para a espécie identificada apenas no Parque Nacional de Mburucuyá, em Corrientes na Argentina. Material preservado em herbário foi avaliado com microscópios estereoscó pico, de luz branca e eletrônico de varredura. A espécie foi descrita e tipificada. Um diagnóstico e uma discussão sobre a distribuição e relação com a morfologia de outras espécies de Isoetes são relatados.

Eleocharis R.Br. (Cyperaceae) no Estado do Rio de Janeiro, Brasil / Eleocharis R. Br. (Cyperaceae) in Rio de Janeiro State, Brasil

Foi realizado o levantamento das espécies de Eleocharis (Cyperaceae) no Estado do Rio de Janeiro - Brasil, a partir de exsicatas depositadas nos principais herbários do Estado (FCAB, GUA, HB, HUNI, R, RB, RBR, RFA, RUSU), assim como coletadas em excursões a ecossistemas aquáticos na área de estudo, entre novembro de 1998 a setembro de 2003. O gênero Eleocharis está representado no Estado do Rio de Janeiro por 19 espécies: Eleocharis acutangula (Roxb.) Schult., E. debilis Kunth, E. elongata Chapm., E. equisetoides (Elliott) Torr., E. filiculmis Kunth, E. flavescens (Poir.) Urb., E. geniculata (L.) Roem. & Schult., E. interstincta (Vahl) Roem. & Schult., E. maculosa (Vahl) Roem. & Schult., E. minarum Boeck.*, E. minima Kunth, E. montana (Kunth) Roem. & Schult., E. mutata (L.) Roem. & Schult., E. nana Kunth, E. pachystyla (C. Wright) C. B. Clarke*, E. radicans (Poir.) Kunth*, E. sellowiana Kunth, E. squamigera Svenson e E. subarticulata (Nees) Boeck (*espécies raras no Estado do Rio de Janeiro). São apresentadas chave de identificação, descrições, ilustrações, informações adicionais de natureza ecológica e distribuição geográfica das espécies de Eleocharis do Estado do Rio de Janeiro.

A floristic inventory of the species of Eleocharis (Cyperaceae) from Rio de Janeiro State - Brazil was made. This research included material from most important Herbaria of Rio de Janeiro (FCAB, GUA, HB, HUNI, R, RB, RBR, RFA, RUSU) as well as plants collected during expeditions to aquatic ecosystems of Rio de Janeiro, between November 1998 and September 2003. The genus Eleocharis is represented in the area by 19 species: Eleocharis acutangula (Roxb.) Schult., E. debilis Kunth, E. elongata Chapm., E. equisetoides (Elliott) Torr., E. filiculmis Kunth, E. flavescens (Poir.) Urb., E. geniculata (L.) Roem. & Schult., E. interstincta (Vahl) Roem. & Schult., E. maculosa (Vahl) Roem. & Schult., E. minarum Boeck.*, E. minima Kunth, E. montana (Kunth) Roem. & Schult., E. mutata (L.) Roem. & Schult., E. nana Kunth, E. pachystyla (C. Wright) C. B. Clarke*, E. radicans (Poir.) Kunth*, E. sellowiana Kunth, E. squamigera Svenson, and E. subarticulata (Nees) Boeck. (*species rare in Rio de Janeiro state). A key of identification, descriptions of species, illustrations, and notes on ecological features and geographical distribution are presented.

Plant growth inhibitory activity of p-hydroxyacetophenones and tremetones from Chilean endemic Baccharis species and some analogous: a comparative study.

Plant growth inhibitory effects of acetophenones 1-6, tremetones 7-12, and MeOH and CH(2)Cl(2) extracts from the aerial parts of Baccharis linnearis, Baccharis magellanica, and Baccharis umbelliformis collected in Chile were assayed as growth inhibitory activity in ranges of 10-500 microM and 0.1-150 ppm, respectively. The effects on seedling growth, germination, and respiration of ryegrass, lettuce, green tomato, and red clover weedy target species were measured. In addition to the inhibitory activity on bleaching of crocin induced by alkoxyl radicals, these compounds also demonstrated scavenging properties toward 2,2-diphenyl-1-picrylhydrazyl in thin-layer chromatography autographic and spectrophotometric assays. In addition, acetophenones and tremetones also showed inhibition of H(+) uptake and oxygen uptake respiration in isolated chloroplasts and mitochondria, respectively. Our results indicate that 1, 4, 7-12, and CH(2)Cl(2) extracts interfere with the dicot preemergence properties, mainly energy metabolism of the seeds at the level of respiration. These compounds appear to have selective effects on the radicle more than shoot growth of dicot seeds. Also, the levels of radicle inhibition obtained with some compounds on Physalis ixocarpa and Trifolium pratense are totally comparable to those of ovatifolin, a known natural growth inhibitor. This behavior might be responsible for its plant growth inhibitory properties and its possible role as an allelopathic agent.

Lacandonia granules are present in Ginkgo biloba cell nuclei.

Lacandonia schismatica is a rare flowering plant with the sex organs spatially inverted. Several aspects of its cell biology are now known. Interestingly, within the cell nucleus, the chromatin is reticulated and it is associated to a novel structure named Lacandonia granules, a very abundant ribonucleoprotein particle showing similarities to perichromatin and Balbiani ring granules, which are involved in nuclear mRNA metabolism. To see whether these particles are present in other plants, we study the nucleus of Ginkgo biloba, a non-flowering plant. Light, electron and atomic force microscopy show that the cell nuclei of G. biloba are reticulated. Ultrastructural analysis showed that in the nucleoplasm, abundant intranuclear particles 32 nm in diameter are present. The EDTA regressive staining suggested that they contain RNA. Ultrastructural in situ hybridization confirmed the presence of RNA in these particles. Therefore, we conclude that the nuclei of G. biloba are reticulated and contain Lacandonia granules. We suggest that these particles may also be present in other plants.

The laticifer system of Chamaesyce thymifolia: a closed host environment for plant trypanosomatids.

Specimens of Chamaesyce thymifolia (Euphorbiaceae) infected and uninfected by Phytomonas sp., a parasite of the Trypanosomatidae family, were anatomically and ultrastructurally analyzed with special emphasis on the laticifer system. C. thymifolia presents branched non-articulated laticifers and was heavily infected by Phytomonas sp. in all collection sites. Infection was often observed in the initial stages inside the vacuole, when the latex particles could be seen. In intermediary stages of laticifer differentiation, Phytomonas sp. were found free in the cytoplasm, inside small vacuoles or in the central vacuole. In differentiated laticifers that had only the plasma membrane, Phytomonas sp. were free in the latex and close to the cell membrane. Infected and uninfected plants showed identical anatomy and ultrastructure and the starch grain numbers in the latex were not reduced in the presence of this flagellate. Biochemical analysis of the latex of infected and uninfected plants presented similar levels of protein, carbohydrate and beta-1,3-glucanase, suggesting that this species is not pathogenic for the host. Besides, all infected plants complete its life cycle. Plants infected with Phytomonas presented occasionally virus like particles and bacteria inside the laticifer tubes.

The laticifer system of Chamaesyce thymifolia: a closed host environment for plant trypanosomatids

Specimens of Chamaesyce thymifolia (Euphorbiaceae) infected and uninfected by Phytomonas sp., a parasite of the Trypanosomatidae family, were anatomically and ultrastructurally analyzed with special emphasis on the laticifer system. C. thymifolia presents branched non-articulated laticifers and was heavily infected by Phytomonas sp. in all collection sites. Infection was often observed in the initial stages inside the vacuole, when the latex particles could be seen. In intermediary stages of laticifer differentiation, Phytomonas sp. were found free in the cytoplasm, inside small vacuoles or in the central vacuole. In differentiated laticifers that had only the plasma membrane, Phytomonas sp. were free in the latex and close to the cell membrane. Infected and uninfected plants showed identical anatomy and ultrastructure and the starch grain numbers in the latex were not reduced in the presence of this flagellate. Biochemical analysis of the latex of infected and uninfected plants presented similar levels of protein, carbohydrate and beta-1,3-glucanase, suggesting that this species is not pathogenic for the host. Besides, all infected plants complete its life cycle. Plants infected with Phytomonas presented occasionally virus like particles and bacteria inside the laticifer tubes.(AU)

New evidence that Lacandonia granules are ultrastructurally related to perichromatin and Balbiani ring granules.

Lacandonia granules are abundant non-typical extranucleolar ribonucleoprotein particles found in the nucleus of Lacandonia schismatica, a rare plant showing spatial inversion of sex organs. In the present study, changes in the number of Lacandonia granules during flower development, and the presence of SR proteins and poly(A)+ RNA in the nuclei of L. schismatica were analyzed by electron microscopy, immunoelectron microscopy and ultrastructural in situ hybridization. Our results show an important reduction in the number of Lacandonia granules in the nuclei of cells of opened (post-anthesis) in relation to unopened (pre-anthesis) flowers, where granules are very abundant. The SR family of splicing factors and poly(A)+ RNA are present in both perichromatin fibers and Lacandonia granules. The developmental behavior, the presence of SR proteins, recently involved in post-splicing events, poly(A)+ RNA and the reported absence of snRNPs splicing factors in Lacandonia granules, suggest that these particles are involved in postranscriptional events as storage and/or transport of mRNAs. A similar situation is present in other nuclear RNP as perichromatin granules present in mammals and Balbiani ring granules of salivary glands of Chironomus. Based on similarities in morphological, developmental behavior, immunocytochemistry and in situ hybridization results, we conclude that Lacandonia, perichromatin and Balbiani ring granules may be also functionally similar structures.

Softening of plant specimens (Equisetaceae) to improve the preparation of paraffin sections.

A method is presented for softening the hard tissues of stem and strobile of Equisetum giganteum allowing the preparation of representative histological slides suitable for teaching and research. Segments of aerial portions of the Equisetum giganteum shoot system were fixed with formaldehyde:ethanol:acetic acid (5:10:5) for 24 hr at room temperature, washed in distilled water and immersed in a mixture of 5% hydrofluoric acid and 0.5% sulfuric acid for 1 hr at room temperature. Hydrofluoric acid has a higher affinity for silica components, and the sulfuric acid acts as a catalyst favoring the separation of calcium silcates. This simple, inexpensive and rapid method allows paraffin sections to be prepared while preserving the topographic microanatomy by decreasing technical artifacts produced by conventional softeners, and preserving PAS-positive polysaccharides.

Chromoplast formation during tomato fruit ripening. No evidence for plastid DNA methylation.

Ripening of tomato fruits involves differentiation of chloroplasts into non-photosynthetic chromoplasts. Plastid DNAs isolated either from green leaf chloroplasts or mature red fruit chromoplasts were compared by restriction endonuclease and DNA/DNA hybridization analyses. The same restriction and gene maps were obtained for both types of DNAs, illustrating the lack of major recombinational events during chromoplast formation. Several enzymes were used that discriminate the presence of methylated bases in their target sequences (Pst I, Pvu II, Sal I, Mbo I/Sau 3AI, Msp I/Hpa II, Bst NI/Eco RII). Plastid DNA fragments generated by these enzymes were hybridized against DNA probes encompassing about 85% of the tobacco chloroplast genome. These probes represented genes that follow very different expression behaviors in response to plastid development. Extensive restriction and hybridization analyses failed to reveal any difference between the chloroplast and chromoplast genomes, indicating that no developmentally related DNA methylation was detected by these methods. The results presented here do not support the hypothesis that selective DNA methylation of the chromoplast genome might play a major role in the transcriptional control of gene expression in these non-photosynthetic plastids.

Subcellular distribution of enzymes of mono- and sesquiterpene biosynthesis in plant tissues.

The biosynthesis of mono- and sesquiterpene precursors and components of essential oils, has been studied isolating enzyme systems from soluble fractions. Improved methods for preparing homogenates from plant tissues, together with a knowledge of its ultrastructure, have allowed to determine that most of the processes of biosynthesis of terpenes, are associated to membranous organelles. The results obtained by different groups are discussed, in order to give an overview of the subcellular distribution of enzymes and specialized organelles, that participate in the biosynthetic processes mentioned above.

Epicuticular wax and water stress in Eragrostis curvala cultivars: I. Morphology and distribution

Se estudió la ultraestructura de la superficie foliar en seis cultivares de pasto llorón, Eragrostis curvula (Schrader) Nees, de diferente grado de tolerancia a la sequía. Mediante microscopía eletrónica de barrido se observó que los cultivares más tolerantes a dicho factor ambiental poseen una capa cerosa apicuticular abaxial más gruesa y compleja que los susceptibles. Por gravimetría se determinó también que en estos cultivares más tolerantes la cantidad total de cera es mayor. Se discute la relación entre la cantidad y distribución de la cera epicuticular y la resistencia a la sequía en esta especie

Epicuticular wax and water stress in Eragrostis curvula cultivars: II. Effect of water stress on the quantity and morphology of epicuticular wax

Se estudió el efecto del déficit hídrico sobre la cantidad, morfología y distribución de la cera epicuticular en dos cultivares de pasto llorón de diferente grado de tolerancia a la sequía. Mediante gravimetría y microscopía electrónica de barrido se encontró que la cantidad de cera epicuticular foliar aumentó luego que las plantas fueron sometidas a un régimen de sequía. Sin embargo, el contenido de cera epicuticular en plantas normalmente regadas de este cultivar es menor que en aquellas pertenecientes al cv. Don Eduardo, más resistentes al estrés hídrico. También se observó un cambio en la morfología de los cristales de cera en tal situación