Elder Antônio Sousa Paiva

Composition and quality of tomato fruit cultivated in nutrient solutions containing different calcium concentrations

Abstract The effect of different calcium (Ca) doses in the nutrient solution used to cultivate tomato plants on the nutrient and carotene levels of tomato (Lycopersicon esculentum Mill. Cv. Jumbo) fruit was studied. The experiment was conducted in a greenhouse hydroponically using a modified Hoagland solution containing different Ca concentrations (0.2, 2.5, 5.0, 10.0, 15.0, and 20.0 mmol L‐1). The experiment was conducted in a fully randomized design with three replications. The fruits of the second and third clusters were picked after full ripening and analyzed for their Ca, magnesium (Mg), potassium (K), lycopene, and total carotene levels. Calcium levels in the fruit increased with increasing Ca concentrations in the nutrient solution, reaching a maximum value of 0.17 dag kg‐1 at a Ca nutrient solution concentration of 19.79 mmol L‐1. In the 0.2 mmol Ca L‐1 treatment, the plants died without reaching fructification. The fruits of the plants treated with 2.5 mmol L‐1 Ca showed blossom‐end rot although ...

Ontogênese, anatomia e ultra-estrutura dos nectários extraflorais de Hymenaea stigonocarpa Mart. ex Hayne (Fabaceae - Caesalpinioideae)

O jatoba-do-cerrado (Hymenaea stigonocarpa Mart. ex Hayne) apresenta nectarios extraflorais (NEFs), os quais sao descritos pela primeira vez no genero. Neste trabalho foram estudadas a distribuicao, ontogenese, estrutura e ultra-estrutura dos nectarios extraflorais (NEFs). Amostras de folhas em varias fases de desenvolvimento foram coletadas, fixadas e processadas para estudos em microscopia de luz e eletronica de transmissao e varredura, segundo tecnicas convencionais. Testes histoquimicos foram empregados para determinar a natureza quimica da secrecao. Os NEFs estao distribuidos por todo o limbo, sendo mais concentrados nos tercos basal e medio de cada foliolo. Estes nectarios sao embutidos no mesofilo, apresentam tecido secretor envolvido por uma endoderme e sao vascularizados por xilema e floema. A atividade secretora dos NEFs e limitada a fase juvenil da folha. Nas folhas mais velhas, os NEFs tornam-se nao funcionais. O tecido secretor dos NEFs e formado a partir da protoderme, enquanto a endoderme tem origem no meristema fundamental. No tecido secretor de nectarios funcionais as celulas apresentam citoplasma denso, nucleo volumoso, mitocondrias, plastidios com sistema de membranas pouco desenvolvido, gotas de oleo dispersas no citosol, dictiossomos e segmentos de reticulo endoplasmatico liso. A secrecao e liberada por meio de rupturas cuticulares e apresenta polissacarideos e lipidios.

Large Plant Samples: How to Process for GMA Embedding?

It is often necessary to process large plant samples for light microscopy studies, but due to structural characteristics of plant tissues, especially intercellular spaces, large vacuoles, and phenolic substances, results are often unsatisfactory. When large samples are embedded in glycol methacrylate (GMA), their core may not polymerize, remaining soft and moist and making it difficult to cut microtome sections. This situation has been erroneously interpreted as the result of poor infiltration, when the soft core of these samples is actually the result of incomplete polymerization. While GMA is in fact present inside samples, unsatisfactory polymerization results from rapid external polymerization that does not allow sufficient hardener to reach the sample core, while the relatively large volume of GMA inside the tissue block also dilutes the hardener. In this chapter we propose a new method for processing large plant specimens that avoids these problems by: (1) slowing the polymerization process through cooling in order to permit the penetration of hardener into the sample core and (2) increasing the hardener:GMA ratio to aid polymerization of the sample core.

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.

Morphological and histological characterization of the osmophores and nectaries of four species of Acianthera (Orchidaceae: Pleurothallidinae)

Nectar and floral odor are frequently associated with the presence and maintenance of specialized pollination systems in Orchidaceae. We studied flowers of four Acianthera species, a genus of myophilous orchids belonging to the largest fly-pollinated orchid group Pleurothallidinae, in order to characterize the secretory structures related to their pollination mechanism. Flowers at anthesis were sampled to detect volatile compounds and nectar; samples were fixed for light microscopy and scanning and transmission electron microscopy. The labellum presents epidermal cells and the first mesophyll layer involved with secretory processes. Cellular characteristics of these regions associated with the occurrence of sugars allowed us to recognize them as nectaries. Some portions of the sepals also shown to be involved with secretory processes and the presence of nitrogenated volatile compounds characterize them as osmophores. The production of nectar in these species makes the occurrence of sapromyophily questionable, even though these flowers present characteristics of this floral syndrome. The presence of osmophores on the sepals reinforces that this localization is common among the Pleurothallidinae, whilst they occur in a different region (labelum) in the other major fly-pollinated orchid group (Bulbophyllum).

Occurrence, structure and functional aspects of the colleters of Copaifera langsdorffii Desf. (Fabaceae, Caesalpinioideae).

Reports concerning colleters in Fabaceae have been scarce, mainly in the Caesalpinioideae subfamily. The present work reports the occurrence, structure, and functional aspects of the colleters of Copaifera langsdorffii. Shoot apices and developing leaves were fixed and processed for examination by light and electron microscopy. Secretion samples were studied to determine their chemical nature and physical properties. The colleters are clavate and occur on the adaxial face of the stipules, petiole and rachis. The secretory stage of the colleters occurs during the leaf expansion, after which these structures turn brown and senesce. The secretion is composed of highly hygroscopic acidic polysaccharides and lipids. The colleters are composed of cells with thin walls, large nuclei, and dense cytoplasm with dictyosomes, mitochondria, plastids and the endoplasmic reticulum. Analyses of the secretion, placement, and functional aspects of the colleters present in C. langsdorffii indicate that these structures help protect young leaves from desiccation.

Ultrastructure and post-floral secretion of the pericarpial nectaries of Erythrina speciosa (Fabaceae).

BACKGROUND AND AIMS The occurrence of nectaries in fruits is restricted to a minority of plant families and consistent reports of their occurrence are not found associated with Fabaceae, mainly showing cellular details. The present study aims to describe the anatomical organization and ultrastructure of the pericarpial nectaries (PNs) in Erythrina speciosa, a bird-pollinated species, discussing functional aspects of these unusual structures. METHODS Samples of floral buds, ovaries of flowers at anthesis and fruits at several developmental stages were fixed and processed by the usual methods for studies using light, and scanning and transmission electron microscopy. Nectar samples collected by filter paper wicks were subjected to chemical analysis using thin-layer chromatography. KEY RESULTS The PNs are distributed in isolation on the exocarp. Each PN is represented by a single hyaline trichome that consists of a basal cell at epidermal level, stalk cell(s) and a small secretory multicellular head. The apical stalk cell shows inner periclinal and anticlinal walls impregnated by lipids and lignin and has dense cytoplasm with a prevalence of mitochondria and endoplasmic reticulum. The secretory cells show voluminous nuclei and dense cytoplasm, which predominantly has dictyosomes, rough endoplasmic reticulum, plastids, mitochondria and free ribosomes. At the secretory stage the periplasmic space is prominent and contains secretion residues. Tests for sugar indicate the presence of non-reducing sugars in the secretory cells. Nectar samples from PNs contained sucrose, glucose and fructose. CONCLUSIONS The secretory stage of these PNs extends until fruit maturation and evidence suggests that the energetic source of nectar production is based on pericarp photosynthesis. Patrolling ants were seen foraging on fruits during all stages of fruit development, which suggests that the PNs mediate a symbiotic relationship between ants and plant, similar to the common role of many extrafloral nectaries.

Role of intermediary cells in Peltodon radicans (Lamiaceae) in the transfer of calcium and formation of calcium oxalate crystals

Com o objetivo de estudar a relacao entre cristais de oxalato de calcio e floema, fragmentos de folhas de Peltodon radicans foram fixados e processados, segundo metodos usuais, para estudos ao microscopio de luz e eletronico de transmissao. Observou-se que os cristais ocorrem nas celulas da bainha do feixe, lateralmente em relacao ao floema. Celulas intermediarias estabelecem conexao entre elemento crivado e celulas da bainha, portadoras de cristais, com crescimento intrusivo entre estas. Ions calcio sao abundantes no citoplasma das celulas da bainha que contem cristais de oxalato de calcio. Nas celulas intermediarias a deteccao ultra-citoquimica de calcio tambem apresentou resultados positivos, enquanto nos elementos crivados a presenca deste ion nao foi constatada. Ha, portanto, um gradiente crescente de concentracao de calcio dos elementos crivados para as celulas da bainha. Assim, formulamos a hipotese de que a formacao de cristais de oxalato de calcio tem, em P. radicans, o objetivo de controlar os niveis de calcio citossolico nos elementos crivados.

Occurrence of blossom‐end rot in tomato as a function of calcium dose in the nutrient solution and air relative humidity

Abstract The effects of different calcium (Ca) concentrations in the nutrient solution and of air relative humidity (RH) on the Ca levels and on the incidence of blossom‐end rot in tomato fruit cv. Jumbo were studied. The experiment was conducted in a greenhouse under hydroponic conditions using a modified Hoagland solution containing different Ca concentrations (0.2, 2.5, 5.0, 10.0, 15.0, and 20.0 mm L‐1) which represented the different treatments. The trial was conducted in a fully randomized design with three replications, with Ca doses representing the plots and environments with high and low RH the subplots. The fruits of the second and third clusters were used, with two fruits per cluster, one maintained at high (90±5%) and the other at low (40±5%) RH. The fruits were picked after full ripening. A greater Ca accumulation was observed in fruits submitted to low RH with this accumulation occurring at all Ca levels in the solution. In the treatment with 100 mg Ca L‐1, the plants died and did not reach ...

Colleters in Caryocar brasiliense (Caryocaraceae) ontogenesis, ultrastructure and secretion

Colleters are widely distributed and have been reported in several taxa. However, the only report of colleters in the Caryocaraceae family is in Caryocar brasiliense. This study purports to describe the distribution, structure and ultrastructure of colleters in C. brasiliense. Vegetative shoot apices with stipules in different stages of development were collected, fixed, and processed by light, transmission and scanning electron microscopy. Colleters occur on the stipule adaxial face and are differentiated on younger stipules, remaining functional until senescence. Stipules are deciduous, falling before the beginning of leaf expansion. Colleter secretion is abundant, filling all the space delimited by the stipule. Colleter origin is mixed, involving the protoderm and ground meristem. In this species, colleters are finger-shaped, consisting of a column of non-secretory central cells and a secretory epithelium whose cells are arranged in palisades. Secretory epithelium cells show dense cytoplasm, rough endoplasmic reticulum (RER) segments, free ribosomes, mitochondria, and abundant well developed dictyosomes. The colleters central cell shows a flocculated cytoplasm and developed vacuole. These cells have a small lobated nucleus with an inconspicuous nucleolus. Mitochondria and RER stand out in the organelles. There is evidence of granulocrine secretion and colleter involvement with protection of the apical meristem and leaves in the initial stages of development.