Marinês Ferreira Pires

Mecanismos anatômicos e fisiológicos de plantas de aguapé para a tolerância à contaminação por Arsênio

This work aimed to evaluate the anatomical and physiological characteristics of Eichhornia crassipes in response to arsenic stress. Plants of E. crassipes were grown in Hoagland hydroponic nutritive solution under greenhouse conditions at five arsenic levels: 0.0, 0.25, 0.50, 1.0 and 2.0 mg L-1 during 20 days. The plants showed an increase in photosynthetic rate, stomatal conductance, transpiration and Ci/Ca rate, as well as in the activity of all the enzymes in the antioxidant system, with higher activity in the leaves than in the roots, in all the treatments with arsenic. The anatomical characteristics observed on the leaves of the plants under higher arsenic levels showed an increase in stomatal density, stomatal index and spongy parenchyma thickness. Root anatomy showed no toxic evidences at any arsenic level; changes in the xylem and phloem characteristics were exhibited by the roots in the arsenic treatments, but no damage was caused to its structure and function. Thus, stress caused by arsenic intoxication at the levels tested, is not evident on E. crassipes plants, and the mechanisms of tolerance of E. crassipes are associated to anatomical and physiological changes.

Lead tolerance of water hyacinth (Eichhornia crassipes Mart. - Pontederiaceae) as defined by anatomical and physiological traits

This study aimed at verifying the lead tolerance of water hyacinth and at looking at consequent anatomical and physiological modifications. Water hyacinth plants were grown on nutrient solutions with five different lead concentrations: 0.00, 0.50, 1.00, 2.00 and 4.00 mg L-1 by 20 days. Photosynthesis, transpiration, stomatal conductance and the Ci/Ca rate were measured at the end of 15 days of experiment. At the end of the experiment, the anatomical modifications in the roots and leaves, and the activity of antioxidant system enzymes, were evaluated. Photosynthetic and Ci/Ca rates were both increased under all lead treatments. Leaf anatomy did not exhibit any evidence of toxicity effects, but showed modifications of the stomata and in the thickness of the palisade and spongy parenchyma in the presence of lead. Likewise, root anatomy did not exhibit any toxicity effects, but the xylem and phloem exhibited favorable modifications as well as increased apoplastic barriers. All antioxidant system enzymes exhibited increased activity in the leaves, and some modifications in roots, in the presence of lead. It is likely, therefore, that water hyacinth tolerance to lead is related to anatomical and physiological modifications such as increased photosynthesis and enhanced anatomical capacity for CO2 assimilation and water conductance.

Etileno e peróxido de hidrogênio na formação de aerênquima em milho tolerante a alagamento intermitente

O objetivo deste trabalho foi avaliar o papel do etileno e do peroxido de hidrogenio (H2O2) na formacao do aerenquima em ciclos de selecao genetica da cultivar de milho BRS 4154, sob alagamento. Plantas dos ciclos C1 e C18 foram submetidas a alagamento por 7 dias, com coleta das raizes aos 0 (controle, sem alagamento), 1 e 7 dias. Foram analisados: a expressao genica das enzimas ACC sintase (ACS), ACC oxidase (ACO), dismutase do superoxido (SOD) e peroxidase do ascorbato (APX); a producao de etileno e o conteudo de H2O2; a atividade da enzima ACO; e a proporcao de aerenquima no cortex. Nao houve expressao de ACS e ACO. Houve variacao na atividade de ACO e na producao de etileno. A expressao da SOD foi maior em plantas C1 e a da APX, em C18, com reducao aos 7 dias. O conteudo de H2O2 nao diferiu entre os tratamentos. A proporcao de aerenquima aumentou com o tempo, tendo sido maior em plantas C18 e relacionada a taxa de formacao do aerenquima. O tempo de alagamento e o nivel de tolerância do ciclo de selecao influenciam a producao do etileno. A expressao da APX indica maior producao de H2O2 no inicio do alagamento.

MICROMORFOMETRIA FOLIAR DE Schinus molle L. (ANARCADIACEAE) EM DIFERENTES ALTURAS NA COPA

A caracterizacao foliar em arvores e essencial para a sua identificacao e utilizacao, bem como para se compreender as suas relacoes com o ambiente. Neste trabalho, objetivou-se o estudo da anatomia dos foliolos e das caracteristicas biometricas das folhas de S. molle em diferentes alturas na copa, em funcao das modificacoes ambientais e fisiologicas promovidas. As folhas foram coletadas em tres diferentes alturas na copa: base, meio e alto da copa em uma populacao cultivada de S. molle. Para as analises anatomicas, as folhas foram fixadas em FAA e armazenadas em etanol sendo, posteriormente, submetidas a seccoes paradermicas e transversais. As lâminas foram fotomicrografadas e as imagens analisadas no software UTHSCSA-Imagetool. Para as analises biometricas foram avaliadas a area, comprimento, largura, massa seca foliares, bem como a area foliar especifica. Os foliolos possuem epiderme unisseriada, estomatos anomociticos e ciclociticos, mesofilo isobilateral e camada subepidermica em ambas as faces da epiderme. Canais secretores e colenquima foram observados na nervura central e bordo dos foliolos. Ocorreram modificacoes nas espessuras da cuticula e do mesofilo, no sistema vascular, espessura do floema e na densidade estomatica de acordo com a altura em que os foliolos se encontram na copa das arvores. As folhas foram menores e demonstram reduzida area foliar para as partes mais altas da copa. A anatomia foliar de S. molle e diferente de outras especies do genero Schinus e demonstra modificacoes sob as diferentes condicoes ambientais e fisiologicas promovidas pelas diferentes alturas na copa.

Growth Curve and Development of the Internal Calli Structure of Eucalyptus camaldulensis Dehn

The objective of this work was to elucidate the growth curve of Eucalyptus camaldulensis Dehn. calli analyzing their anatomical modifications. A sigmoid aspect of the growth curve of the calli fresh matter was observed, with five different phases (lag, exponential, linear, deceleration and decline). In the lag phase, the highest growth percentage 87%, was observed, which reduced during the evaluation period to 17% in the linear phase. As for the anatomical analyses, cellular multiplications was observed during the lag and exponential phases and increase in cell size during the linear phase, promoting the calli volume growth and the establishment of the globular conformation.

Anatomical and physiological modifications in water hyacinth under cadmium contamination

The pollution of water bodies with heavy metals is generating increasing concern worldwide, and among those heavy metals, cadmium is one of the most toxic elements released into the environment. The present study aimed to evaluate the anatomical and physiological modifications adopted by the water hyacinth ( Eichhornia crassipes ) under cadmium contamination. The plants were grown in Hoagland solution in a greenhouse at five cadmium levels: 0.00, 3.5, 7.0, 14.0, and 28.0 μM. The net photosynthesis, stomatal conductance, transpiration rate, Ci/Ca ratio, antioxidant system enzymes activity, and anatomical traits in plant roots and leaves were evaluated. The plants exhibited increased photosynthesis, stomatal conductance, transpiration, and Ci/Ca ratios in all treatments containing cadmium. Antioxidant system enzymes displayed increased activity in the roots and leaves of plants treated with cadmium. Plants exhibited higher stomatal density and spongy parenchyma thickness under Cd contamination. The anatomical traits of the roots exhibited no evidence of toxicity or improved vascular system traits. Thus, Eichhornia crassipes demonstrated an ability to tolerate Cd by adopting changes in the anatomy, gas exchange and antioxidant system.

MICROMORFOMETRIA FOLIAR DE PALICOUREA RIGIDA KUNTH. (RUBIACEAE) EM AMBIENTE DE CERRADO E CAMPO RUPESTRE

The objective of this work was to evaluate qualitative and quantitative leaf anatomical traits of Palicourea rigida Kunth. (Rubiaceae) species occurring in the Brazilian Cerrado and Campo Rupestre ecosystems. Anatomical analysis was performed in fresh or fixed leaves processed with usual plant microtechnique. Leaves showed uniseriate epidermis in petiole and leaf blade which contains uniseriate nonglandular tricomes (tector type) occurring only over the vascular bundles. Likewise, paracytic stomata were found only in abaxial side of the leaf surface. The mesophyll contains uniseriate palisade parenchyma and multiseriate spongy parenchyma (nine layers) which showed cells with different morphology and size. Crystal idoblasts of different types were observed in both the petiole and leaf blade. Collateral vascular bundles were found both in the petiole and leaf blade. Leaf venation type was pinnate, campylodromous or brochydodromous. The micromorphometric analysis showed significant differences from plants of different environments for all leaf characteristics and Cerrado plants showed higher means for all evaluated traits. Therefore, the influence of environments may had modulated morphological responses in P. rigida, since no difference was found in the type or distribution of leaf tissues in Cerrado or Campo Rupestre.

Óleo essencial de Chenopodium ambrosioides L.: estruturas secretoras, atividade antibacteriana e antioxidante

The aim of this study was to evaluate the antibacterial and antioxidant activities of essential oil from Chenopodium ambrosioides L. and to determine its secretory structures. The essential oil was extracted through the hydrodistillation technique using a modified Clevenger apparatus (2 hours) and chemically characterized by GC/MS and GC-FID. The antioxidant activity was determined by monitoring the reduction of 2,2-diphenyl-1-picrylhydrazyl (DPPH) and by the oxidation of the β-carotene/linoleic acid system. The evaluation of antibacterial activity was performed by the agar cavity diffusion technique using the microorganisms Staphylococcus aureus, Listeria monocytogenes, Escherichia coli and Salmonella Cholerasuis. The characterization of trichomes was accomplished by Scanning Electron Microscopy (SEM) and histochemical tests with Nadi and Sudan IV reagents. The antioxidant activity demonstrated by the β-carotene/acid linoleic test, with IC50 = 455.7 μg mL. This oil also presented antibacterial activity for both Gram-negative and Gram-positive bacteria. The minimal inhibitory concentration ranged 62.5 to 250 μL mL. The presence of terpenes in the glandular trichomes was observed, suggesting that the essential oil is secreted by these structures.