Navegando por Autor "Araújo, João Marcos de"
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Item Anatomy of the floral, bract, and foliar nectaries of Triumfetta semitriloba (Tiliaceae)(Canadian Journal of Botany, 2005) Meira, Renata Maria Strozi Alves; Azevedo, Aristéa Alves; Araújo, João Marcos de; Silva, Kellen Lagares Ferreira; Leitão, Carlos André Espolador; Collevatti, Rosane GarciaTriumfetta semitriloba Jacq. (Tiliaceae) is a tropical weedy species with floral nectaries and glands located at the margins of the leaves. The objectives of this work were to describe the anatomy of these secretory structures and to analyze their exudates. Sucrose, glucose, and fructose were identified in the product released by these secretory structures, characterizing them as nectaries. The nectaries of T. semitriloba are of a specialized type; a secretory epidermis comprised of pluricellular and multiserial nectariferous trichomes covers a nectariferous parenchyma, vascularized by phloem and xylem. A mass of phenolic compounds occurs in the head cells of the nectariferous trichomes of the foliar and bract nectaries; however, it is absent in trichomes of the floral nectary. The leaf and bract nectaries differed from those from flowers in their length and diameter. Structural features of the nectaries of T. semitriloba are typical of other taxa of the Malvales.Item Effects of simulated acid rain on the foliar micromorphology and anatomy of tree tropical species(Environmental and Experimental Botany, 2006-12) Sant’Anna-Santos, Bruno Francisco; Silva, Luzimar Campos da; Azevedo, Aristéa Alves; Araújo, João Marcos de; Alves, Ericka Figueiredo; Silva, Eldo Antônio Monteiro da; Aguiar, RosaneIn order to correlate sintomatology with anatomical alterations caused by acid rain in leaves of tropical species, seedlings and saplings of Spondias dulcis Forst. F., Mimosa artemisiana Heringer and Paula and Gallesia integrifolia (Spreng.) Harms were exposed to simulated low-pH acid rain (pH 3.0). Control plants were submitted only to rain with distilled water (pH 6.0). The plants were exposed daily to the acid rain for 20 min for 10 consecutive days. Necrotic spots on the leaf blade occurred and most of the injuries onset on the epidermis in all species studied. S. dulcis displayed epicuticular wax erosion and rupture of epidermis. The abaxial surface of M. artemisiana was colonized by a mass of fungi hyphae and stomatal outer ledge rupture occurred. Some epidermal cells of G. integrifolia showed appearance similar to plasmolysis. The plants accumulated phenolic compounds in necrotic areas. Afterwards, leaves presented injuries in the mesophyll and collapsed completely. Cells surrounding the injured areas accumulated starch grains in S. dulcis. M. artemisiana showed more drastic symptom intensity in response to acidic rain. S. dulcis displayed visual symptoms similar to G. integrifolia, however, anatomical alterations were more severe.Item Rheological and physicochemical studies on emulsions formulated with chitosan previously dispersed in aqueous solutions of lactic acid(Food Biophysics, 2017-01-18) Soares, Lucas de Souza; Faria, Janaína Teles de; Amorim, Matheus Lopes; Araújo, João Marcos de; Minim, Luis Antonio; Coimbra, Jane Sélia dos Reis; Teixeira, Alvaro Vianna Novaes de Carvalho; Oliveira, Eduardo Basílio deChitosan, a natural, cationic polysaccharide, may be a hydrocolloid strategic to formulate acidic food products, as it can act as both bio-functional and technofunctional constituent. Typically, acetic acid is used to disperse chitosan in aqueous media, but the use of this acid is limited in food formulations due to its flavor. In this study, chitosan was firstly dispersed (0.1% m/V) in lactic acid aqueous solutions (pH 3.0, 3.5 or 4.0), and then evaluated regarding its thickener and emulsion stabilizer properties. O/W emulsions were prepared and characterized in terms of rheological properties, droplets average diameters and droplets ζ-potential. Emulsions containing chitosan were 3 times more viscous than controls without chitosan, and presented storage modulus (G’) higher than loss modulus (G”). Furthermore, they displayed two different populations of droplets (average diameters of 44 and 365 nm) and positive ζ-potential values (+50 mV). Droplets average diameters and ζ-potential did not present significant changes (p > 0.05) after storage at 25 °C during 7 days. This study showed that i) food organic acids other than acetic acetic acid can be used to disperse chitosan for technological purposes, and ii) chitosan dispersed at very low concentrations (0.1 m/V %) had relevant effects on rheological and physicochemical aspects of food-grade emulsions.Item Utilização de parâmetros morfoanatômicos na análise da fitotoxidez do flúor em folhas de Magnolia ovata (A. St.-Hil.) Spreng. (Magnoliaceae)(Revista Árvore, 2007-03-29) Sant'Anna-Santos, Bruno Francisco; Duque-Brasil, Reinaldo; Azevedo, Aristéa Alves; Silveira, Alice de Souza; Araújo, João Marcos de; Aguiar, RosaneCom os objetivos de avaliar o grau de suscetibilidade e caracterizar as injúrias na morfoanatomia de folhas de Magnolia ovata, mudas foram submetidas à chuva simulada com flúor (10 µg.ml-1 de F-) por 10 dias consecutivos. No tratamento controle, utilizou-se apenas água deionizada. Folhas foram coletadas para quantificação de flúor na matéria seca e fixadas para análises em microscopia de luz e eletrônica de varredura. As folhas apicais apresentaram pequena porcentagem de necroses intervenais e marginais em uma ou ambas as faces e maior acúmulo de flúor, em relação ao controle, quando comparadas com as folhas da porção basal. A análise micromorfológica das folhas aparentemente sadias indicou alterações nas paredes periclinais externas da epiderme e formação de concavidades, além de cristas estomáticas danificadas, erosão de ceras epicuticulares e presença de esporos e hifas de fungos. A caracterização estrutural das injúrias evidenciou retração de protoplasto das células epidérmicas, colapso das células do mesofilo e da epiderme e acúmulo de compostos fenólicos em células das regiões necrosadas. As alterações micromorfológicas das folhas ocorreram antes que sintomas fossem observados, o que comprova a importância da micromorfologia na diagnose precoce da injúria. As plantas de M. ovata apresentaram poucos sintomas visuais em resposta ao flúor, entretanto as alterações morfoanatômicas indicam que essa espécie possui potencial para ser utilizada como bioindicadora.