Anatomia do eixo vegetativo aéreo de Protium heptaphyllum (Aubl.) Marchand. (Burseraceae) com ênfase no sistema secretor em ambiente com influência das marés
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Data
2017-02-15
Autores
Rodrigues, Maria Ivanilde de Araujo
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Universidade Estadual Paulista (Unesp)
Resumo
Protium heptaphyllum (Aubl.) Marchand é uma espécie arbórea de Burseraceae importante na produção de resina com elevado valor econômico e ecológico bastante utilizada na produção de fármacos, cosméticos, repelentes, inseticidas e incensos. Apresenta grande plasticidade no que se refere aos ambientes de ocorrência, sendo encontrada em áreas com solos inundáveis, argilosos ou arenosos, secos ou úmidos, o que justifica sua ampla utilização em projetos de restauração em áreas inundáveis ou não. No litoral do Maranhão, populações de P. heptaphyllum ocorrem em áreas naturalmente alagáveis pelo pulso das marés e em áreas não-alagáveis. Sabe-se que o alagamento e a salinidade do solo podem influenciar o desenvolvimento das plantas promovendo alterações morfológicas que pode refletir na herbivoria. Entretanto, estudos sobre os aspectos estruturais de seus órgãos vegetativos estão faltando, principalmente no que se refere aos sítios secretores de substâncias bioativas. Diante disso, este trabalho teve como objetivo investigar as características anatômicas em caules e folhas de indivíduos de P. heptaphyllum em ambiente alagável pelas marés e não alagável na restinga maranhense; verificar se a tolerância ao alagamento influencia na herbivoria foliar, analisar e descrever a morfologia, distribuição, as principais classes de compostos produzidos, assim como os estágios iniciais de desenvolvimento dos espaços secretores. Amostras de folhas e caule em estrutura primária e secundária foram processadas segundo técnicas usuais em anatomia vegetal. Dados quantitativos sobre os tecidos/células foliares e caulinares foram obtidos e analisados ao microscópio de luz e submetidos ao teste Tstudent. As porcentagens das áreas foliares consumidas estimadas com auxilio de programa de edição de imagens foram submetidas à ANOVA. As folhas de P. heptaphyllum são hipostomáticas, heterobáricas, mesofilo dorsiventral; o sistema vascular na nervura principal envolto por uma calota de fibras lignificadas. No caule em estrutura primária, cristais de oxalato de cálcio e esclereides são abundantes no córtex externo; uma bainha de fibras gelatinosas delimita externamente o cilindro vascular. No caule em estrutura secundária, a periderme apresenta lenticelas de tamanhos variados; floema desenvolvido e abundância de esclereides em sua porção mais externa; o xilema secundário apresenta elementos de vasos com tilos. Espaços secretores (i.e., canais e cavidades) e idioblastos ocorrem associados ao floema do caule e da nervura principal de folhas; nas nervuras foliares imersas no mesofilo foram encontradas cavidades secretoras. Os espaços secretores constituídos por epitélio unisseriado e lume amplo se originam por processo esquizógeno e se expandem por esquizolisigenia. Canais secretores podem se ramificar e se unir a espaços secretores vizinhos formando uma rede secretora anastomosada. Lipídios, compostos fenólicos, terpenos e polissacarídeos foram detectados através de análises histoquímicas nos espaços secretores e nos idioblastos e podem ser importantes na defesa da planta contra herbívoros e patógenos e na proteção contra fatores abióticos como alta intensidade luminosa e dessecação. No que se refere aos dados quantitativos, indivíduos do ambiente alagável apresentaram maior área ocupada pelos espaços intercelulares no parênquima lacunoso das folhas, sistema secretor mais desenvolvido em folhas e caule e maior porcentagem de vasos agrupados no xilema secundário do caule. As áreas foliares consumidas por herbívoros não variaram entre os indivíduos dos dois ambientes. Os órgãos vegetativos aéreos de P. heptaphyllum da restinga, apresentam de forma geral, um misto de caracteres mesomórficos e xeromórficos. Com base nos resultados encontrados a espécie P. heptaphyllum, apresenta grande plasticidade no que se refere aos ambientes de ocorrência e por ser tolerante ao alagamento podemos recomendá-la em programas de restauração de vegetação em locais sujeitos a inundações.
Protium heptaphyllum (Aubl.) Marchand is a Burseraceae tree important in production of resin with high economic and ecological values, which is widely employed to produce drugs, cosmetics, repellent, insecticides and incenses. This species presents great plasticity concerning the growing environments and it is found in semideciduous forest, cerrado, restinga (“sandy coastal plains”) and riparian forests, in areas with flooding, clay or sandy, dry or wet soils, justifying its using in projects of degraded areas restoration. In Maranhão coast, populations of P. heptaphyllum occur in areas naturally flooded by the tide pulse and in non-flooded areas. It is known that the soil flooding and salinity can influence the plant development causing morphological alterations can reflect in the herbivory. However, studies on the structural features of its vegetative organs are lacking, mainly concerning the sites of production of the bioactive compounds. The objective of this study was to investigate the anatomical characteristics of P. heptaphyllum stems and leaves in tidal floodplain and not flooded in the Maranhão restinga, and if flood tolerance influences foliar herbivory, as well as describe the distribution, morphology, the main classes of compounds produced and the initial stages of development of secretory spaces. Stem and leaf samples were processed according to usual techniques in plant anatomy. Quantitative anatomical data were obtained under light microscope and submitted to T-student test. The percentage of consumed leaf areas were estimated using image editing program and submitted to ANOVA. The leaves of P. heptaphyllum are hipostomatic, heterobaric and present dorsiventral mesophyll; the vascular system in the midrib is surrounded by a sheath of lignified fibers. In the primary stem, calcium oxalate crystals and sclereids are abundant in the outer cortex; a sheath of gelatinous fibers surrounds the vascular cylinder. In the secondary stem, the periderm present lenticels with variable sizes; the phloem is developed and present abundant sclereids in the outer portion; the secondary xylem present vessel members with tylosis. Secretory spaces (i.e., canals and cavities) and idioblasts occur in the phloem of stem and midrib; in the vein immersed in the leaf mesophyll, secretory cavities were observed. The secretory spaces constituted by uniseriate epithelium and wide lumen originate by schyzogenous process and expand by schyzolysigenesis. The secretory canals can branch and fuse with neighboring secretory spaces originating an anastomosing secretory network. Lipids, phenolic compounds, terpenes and polysaccharides were detected by histochemical analysis in secretory spaces and idioblasts and can be important in the plant defense against herbivores and pathogens and in the protection against abiotic factors as high light intensity and desiccation. Concerning the quantitative data, individuals from the floodable environment presented greater area occupied by intercellular spaces in the leaf spongy parenchyma, more developed secretory system in leaves and primary and secondary stems and higher percentage of grouped vessels in the stem secondary xylem. The leaf areas consumed by herbivores did not vary among individuals of the different environments. The aerial vegetative organs of P. heptaphyllum from the restinga present, in a general way, a mixture of mesomorphic and xeromorphic characters. Based on the reduced number of structural characters that presented variations among individuals of P. heptaphyllum from both environments, we can suggest that this species is tolerant to the flooding, emphasizing its importance in programs of vegetation restoration in sites subjected to flooding.
Protium heptaphyllum (Aubl.) Marchand is a Burseraceae tree important in production of resin with high economic and ecological values, which is widely employed to produce drugs, cosmetics, repellent, insecticides and incenses. This species presents great plasticity concerning the growing environments and it is found in semideciduous forest, cerrado, restinga (“sandy coastal plains”) and riparian forests, in areas with flooding, clay or sandy, dry or wet soils, justifying its using in projects of degraded areas restoration. In Maranhão coast, populations of P. heptaphyllum occur in areas naturally flooded by the tide pulse and in non-flooded areas. It is known that the soil flooding and salinity can influence the plant development causing morphological alterations can reflect in the herbivory. However, studies on the structural features of its vegetative organs are lacking, mainly concerning the sites of production of the bioactive compounds. The objective of this study was to investigate the anatomical characteristics of P. heptaphyllum stems and leaves in tidal floodplain and not flooded in the Maranhão restinga, and if flood tolerance influences foliar herbivory, as well as describe the distribution, morphology, the main classes of compounds produced and the initial stages of development of secretory spaces. Stem and leaf samples were processed according to usual techniques in plant anatomy. Quantitative anatomical data were obtained under light microscope and submitted to T-student test. The percentage of consumed leaf areas were estimated using image editing program and submitted to ANOVA. The leaves of P. heptaphyllum are hipostomatic, heterobaric and present dorsiventral mesophyll; the vascular system in the midrib is surrounded by a sheath of lignified fibers. In the primary stem, calcium oxalate crystals and sclereids are abundant in the outer cortex; a sheath of gelatinous fibers surrounds the vascular cylinder. In the secondary stem, the periderm present lenticels with variable sizes; the phloem is developed and present abundant sclereids in the outer portion; the secondary xylem present vessel members with tylosis. Secretory spaces (i.e., canals and cavities) and idioblasts occur in the phloem of stem and midrib; in the vein immersed in the leaf mesophyll, secretory cavities were observed. The secretory spaces constituted by uniseriate epithelium and wide lumen originate by schyzogenous process and expand by schyzolysigenesis. The secretory canals can branch and fuse with neighboring secretory spaces originating an anastomosing secretory network. Lipids, phenolic compounds, terpenes and polysaccharides were detected by histochemical analysis in secretory spaces and idioblasts and can be important in the plant defense against herbivores and pathogens and in the protection against abiotic factors as high light intensity and desiccation. Concerning the quantitative data, individuals from the floodable environment presented greater area occupied by intercellular spaces in the leaf spongy parenchyma, more developed secretory system in leaves and primary and secondary stems and higher percentage of grouped vessels in the stem secondary xylem. The leaf areas consumed by herbivores did not vary among individuals of the different environments. The aerial vegetative organs of P. heptaphyllum from the restinga present, in a general way, a mixture of mesomorphic and xeromorphic characters. Based on the reduced number of structural characters that presented variations among individuals of P. heptaphyllum from both environments, we can suggest that this species is tolerant to the flooding, emphasizing its importance in programs of vegetation restoration in sites subjected to flooding.
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Palavras-chave
Alagamento, Anatomia, Breu-branco, Caule, Estruturas secretoras, Folha, Herbivoria foliar, Anatomy, Flooding, Herbivory, Leaf, Secretory, Structures