Cláudia Regina Gontijo Labory

Anatomy and ultrastructure alterations of Leucaena leucocephala (Lam.) inoculated with mycorrhizal fungi in response to arsenic-contaminated soil

Many studies demonstrate the potential application of arbuscular mycorrhizal fungi (AMF) for remediation purposes, but little is known on AMF potential to enhance plant tolerance to arsenic (As) and the mechanisms involved in this process. We carried anatomical and ultrastructural studies to examine this symbiotic association and the characteristics of shoots and roots of Leucaena leucocephala in As-amended soils (35 and 75 mg As dm(-3)). The experiment used 3 AMF isolates from uncontaminated soils: Acaulospora morrowiae, Glomus clarum, and Gigaspora albida; a mixed inoculum derived from combining these 3 isolates (named Mix AMF); and, 3 AMF isolates from As-contaminated areas: A. morrowiae, G. clarum and Paraglomus occultum. Phytotoxicity symptoms due to arsenic contamination appeared during plant growth, especially in treatments without AMF application. Inoculation with G. clarum and the mixture of species (A. morrowiae, G. albida, and G. clarum) resulted in better growth of L. leucocephala in soils with high As concentrations, as well as significant As removal from the soil, showing a potential for using AMF in phytoextraction. Light microscopy (LS), transmission (TEM) and scanning electron microscopies (SEM) studies showed the colonization of the AMF in plant tissues and damage in all treatments, with ultrastructural changes being observed in leaves and roots of L. leucocephala, especially with the addition of 75 mg dm(-3) of As.

Induction and characterization of oil palm (Elaeis guineensis Jacq.) pro-embryogenic masses

Oil palm is one of the most economically valuable oil seed plants, but the expansion of plantations has been limited by availability of seedlings, as the conventional propagation is through seeds, which have low germination rates. One possible solution for the large-scale production is the use of somatic embryogenesis. The aim of this study was evaluate the effects auxins 2,4-D and picloram on the induction of pro-embryogenic masses in E.guineenesis hybrid leaf explants and characterize, regarding embryogenic characteristics, with cytochemical and ultrastructural analysis. Specifically, in vitro plantlets leaves fragments were inoculated in Y3 culture medium supplemented by 2.4-D or picloram at different concentrations (0.0, 1.0, 3.0, 6.0 and 9.0 mg l⁻¹). After 90 days the presence/ absence of cell masses were evaluated. Both growth regulators efficiently induced cellular masses regardless of the concentrations applied. As the cell masses were not homogeneously formed, they were classified according to color and shape into four types: TYPE 1--elongated and translucent, TYPE 2--uneven and translucent, TYPE 3--globular and beige, TYPE 4--globular and white. Based on the anatomical and ultrastructural features, TYPE 2, 3 and 4 cell masses were considered to have the highest embryogenic potential and therefore may be most suited to large-scale vegetative propagation of oil palm.

Applications in environmental bioinorganic: Nutritional and ultrastructural evaluation and calculus of thermodynamic and structural properties of metal-oxalate complexes

Lead (Pb) is known by its toxicity both for animals and plants. In order to evaluate its toxicity, plants of Brachiaria brizantha were cultivated on nutritive solution of Hoagland during 90 days and submitted to different concentrations of Pb. The content of macro and micronutrients was evaluated and there was a reduction on root content of Ca, besides the lowest dosages of Pb had induced an increase of N, S, Mn, Cu, Zn and Fe. The cell ultrastructure of leaves and roots were analyzed by transmission electronic microscopy (TEM). Among the main alterations occurred there were invaginations on cell walls, the presence of crystals on the root cells, accumulation of material on the interior of cells and vacuolar compartmentalization. On the leaves the degradation of chloroplasts was observed, as well as the increase of vacuoles. Structures for the formation of oxalate crystals were proposed through molecular modeling and thermodynamic stability. Calculi suggest the formation of highly stable metal-oxalate complexes.

Cytological characterization of Jatropha curcas callus in different periods of cultivation

The aimed was characterization and determining the time for Jatropha curcas callus subculture. The pattern of J. curcas callus development is sigmoidal with 5 distinct phases, and transplantation should be performed at the end of the deceleration phase (approximately day 28). During callus development, it was observed that at the onset of growth in the exponential phase the cells were internally disorganized; in the linear phase, respiratory metabolism was resumed through reorganization of the first mitochondria; and by the mid-deceleration phase, the cells were entirely active, and several organelles were detected. This organizational status was maintained throughout the stationary phase during which somatic pre-embryos were identified. At the end of the stationary phase, intracellular disruption began, and the cells entered senescence, which characterized the decline phase for the J. curcas calli growth curve.

Essential oils and whole milk in the control of soybean powdery mildew

This research aimed to evaluate the potential of essential oils (EOs) and cows whole milk (CWM) in order to control soybean powdery mildew and to estimate the most effective concentrations of these natural products in reducing the disease severity on soybean plants. Three experiments were carried out: The first experiment evaluated and selected the most effective treatments to reduce the severity of soybean powdery mildew under greenhouse conditions; the second experiment evaluated the effect of CWM and EOs of citronella, lemongrass, eucalyptus, cinnamon and tea tree on the pathogen through the ultrastructure analysis of soybean leaflets infected by Erysiphe diffusa using the scanning electron microscope (SEM) and light microscope (LM) technology. In the third experiment, the most effective products were tested at several concentrations in order to define the most effective concentrations to reduce disease severity under greenhouse conditions. The treatments CWM (100mL L-1) and EOs of citronella, lemongrass and eucalyptus (1.0mL L-1), reduced the disease severity from 67 to 74%. Direct effects from all natural products tested on the structures of E. diffusa were demonstrated through the SEM and LM analysis. Concentrations at 1.5mL L-1 for EOs of citronella, lemongrass and eucalyptus and also at 180mL L-1 for the treatment CWM were the most effective against E. diffusa on soybean.

ALTERAÇÕES ANATÔMICAS EM ESPÉCIE DE GRAMÍNEA CULTIVADA EM SOLO DE ÁREA DE MINERAÇÃO DE ZINCO TRATADO COM MATERIAIS AMENIZANTES

Concentracoes elevadas de elementos-traco em solos podem representar riscos ao ambiente e aos humanos. Diante disso, diversas tecnologias tem sido utilizadas para mitigar estes riscos, sendo a fitorremediacao uma tecnica de baixo custo e ambientalmente correta. Plantas expostas a altas concentracoes de elementos-traco podem vir a apresentar alteracoes anatomicas e ultraestruturais em resposta a fitotoxidez. Materiais amenizantes podem minimizar essas alteracoes, visto que alem de reduzirem a fitodisponibilidade destes elementos, tambem podem melhorar as condicoes do solo. Neste contexto, estudos que utilizam a Microscopia Eletronica para avaliacao destas alteracoes ocorridas em plantas tornam-se de grande valia na avaliacao de possiveis efeitos de estresse para as estruturas celulares internas, bem como para entender possiveis mecanismos de tolerância das especies. A Microscopia Eletronica de Varredura (MEV) tem evoluido na direcao de dar nao apenas informacoes ultraestruturais, mas tambem analiticas das amostras estudadas. Contando ainda com um detector de dispersao de Raios-X, pode-se, atraves da tecnica da Espectroscopia de Energia Dispersiva (EDS), alem de gerar imagens, determinar a composicao quimica do especime em estudo. Objetivou-se com este trabalho evidenciar, por meio de analises qualitativas e quantitativas usando MEV/EDS, possiveis alteracoes anatomicas e ultraestruturais em Andropogon sp. cultivado em solos de areas de mineracao de zinco tratados com materiais amenizantes. O experimento foi conduzido em casa de vegetacao, utilizando-se tres solos, dois materiais amenizantes, 2 doses de cada material amenizante e tres repeticoes. Os amenizantes foram incubados por 60 dias e, apos esse periodo, realizou-se a semeadura de 15 sementes de Andropogon sp., autoctone de uma area de mineracao de zinco localizada em Vazante (MG). Apos o cultivo, amostras de folhas e raizes foram analisadas por MEV/EDS. As plantas apresentaram folhas com desestruturacao do mesofilo, deformacao em celulas epidermicas e em celulas da bainha dos feixes vasculares. As raizes apresentaram as celulas epidermicas, do cortex e da medula deformadas e rompidas, alem de vasos do cilindro vascular rompidos. Foram localizadas, tambem, em celulas epidermicas, feixes vasculares, cortex e medula estruturas diferenciadas e, ou, cristais que continham teores significativos de Zn e Pb. O residuo de carvao foi eficiente como amenizante da fitotoxidez causada por ETs como Zn, Cd e Pb, reduzindo o estresse e, consequentemente, as alteracoes anatomicas nas plantas. Por outro lado, o lodo de esgoto nao apresentou a mesma eficiencia. Andropogon sp. foi capaz de sobreviver as alteracoes atraves de mecanismos de acumulo de Zn e Pb em estruturas e, ou cristais.