Terezinha Rangel Camara

Antimicrobial action of the essential oil of Lippia gracilis Schauer

Avaliou-se a atividade antimicrobiana do oleo essencial (OE) de Lippia gracilis Schauer sobre fungos contaminantes de laboratorios de cultura de tecidos vegetais e bacterias endofiticas de heliconias. Discos de micelio dos fungos Geotrichum candidum; Trichoderma viride; Torula herbarum; Paecillomyces sp.; Aspergillus nidulans; Fusicoccum sp.; A. flavus; P. aeruginens; Curvularia lunata e A. niger, foram inoculados em meio BDA com oleo (0; 420; 440; 460; 480 e 500 µL L-1). O percentual de inibicao em 420 µL L-1 foi de 100% para todos os fungos exceto paraC. lunata and A. niger, o qual foi de 95.58% and 89.40% respectivamente. Em outro experimento, suspensao das especies Salmonela choleraceuis-diarizonae, Enterobacter asburiae, Bacillus thuringiensis, B. pumilus, Klebsiella pneumoniae, E. hormaechei, Bacillus pumilus, B. cereus, B. pumilus foi individualmente adicionada ao meio NYDA, que foi vertido em placas de Petri e, apos solidificado, perfurado e preenchido com agua ou oleo (420 µL L-1). Avaliou-se o diâmetro do halo de inibicao. Avaliou-se tambem, a inibicao em meio liquido. K. pneumoniae foi a especie bacteriana menos sensivel e E. hormaechei foi a mais sensivel.

Polyamine and free amino acid variations in NaCL-treated embryogenic maize callus from sensitive and resistant cultivars

Summary The effect of different NaCl concentrations on maize embryogenic calluses derived from immature embryo cultures of a) the salt-sensitive inbred line W64Ao2, b) the resistant hybrid Arizona 8601 and c) the 0.4% NaCl pre-adapted W64Ao2 (WpA) calluses was studied. The effect of salt stress on growth as well as on polyamine (putrescine, spermidine and spermine) and amino acid contents of the treated calluses was determined. Enzymatic activities of the polyamine biosynthetic enzymes arginine and ornithine decarboxylase were also analyzed. A significant decrease in the growth of calluses in relation to increased salt concentrations and to the tolerance of the callus was observed. Embryogenic Arizona calluses showed the lowest growth inhibition and W64Ao2 calluses the highest inhibition after 60 days of culture in saline medium. WpA calluses showed an intermediate response. At high-salt concentrations (1.2–2.0%), calluses showed a significant increase in total polyamine content, especially caused by a rise in putrescine. This increase was proportionally higher for Arizona and WpA than for W64 calluses. Whereas the spermidine content of Arizona calluses was augmented with salt, a spermidine decrease was observed for W64 from 0.8 % NaCl. Arginine decarboxylase activity increased from 1.2 to 2.0 % NaCl for Arizona calluses, while in W64 calluses this increase was lower than in Arizona up to 2.0 %. With respect to free amino acid contents, the levels of free proline, which represent 50 % of the total free amino acid content, decreased with increasing salt in the medium. The highest amino acid increases were observed for arginine, alanine, glutamine, glutamic acid and y-aminobutyric acid. Arginine decarboxylase activity showed significant increments in relation to salt stress, which may be related to putrescine and some amino acid variations. Relationships between all the analyzed parameters and the polyamine synthesis and degradation processes under stress conditions are discussed.

Geração e desintoxicação enzimática de espécies reativas de oxigênio em plantas

The biotic and abiotic stress conditions imposed on plants induces overproduction of reactive oxygen species (ROS), which can cause damage to cellular structures and even lead to the death of the plant. The biochemical and physiological responses of higher plants to oxidative stress includes an efficient antioxidant defense system, which involves the activity of the enzymes superoxide dismutase, catalase, ascorbate peroxidase, peroxiredoxines, among others, in addition to non-enzymatic metabolites, which, together, work on eliminating the ROS and in reducing oxidative damage. This review will address the main production sites of ROS and the action of some enzymes of antioxidative defense system in plants.

Estresse salino em duas variedades de cana-de-açúcar: enzimas do sistema antioxidativo e fluorescência da clorofila

Brazil is seen as being the largest producer of sugarcane (Saccharum officinarum L.) and of mastering all stages in the production of sugar and ethanol. Currently this production is being expanded into the semi-arid regions of Brazil, where there are soil-types prone to salinity. This study aimed to evaluate the response to salinity in two sugarcane genotypes, RB867515 and RB863129. Salinity caused an increase in chlorophyll fluorescence and a reduction of chlorophyll concentration in both varieties. The reduction of chlorophyll however was higher in RB867515. In this same type, an increase in the activity of ascorbate peroxidase (APX) and catalase (CAT) was observed, while in genotype RB863129 there was a reduction in the activity of these two enzymes. These results show that RB867515 has a mechanism which better protects the plant against damage to the photochemical system and the action of reactive oxygen species, particularly H 2 O 2 .

In vitro selection of salt tolerant 'Nanicão' banana buds.

This work aims to evaluate the effect of NaCl and to make selections of banana cv. Nanicao (AAA) in vitro. Buds were grown on MS medium with 2.5 mg L-1 BAP and supplemented with different NaCl concentrations (0; 20; 40; 60; 80; 100 and 120 mM), for 60 days (Phase I). Survivor buds were transferred to salt-free media and grown for 30 days (Phase II). Afterwards they were submitted to MS media containing 80 or 100 mM NaCl, during 90 days (Phase III). One hundred buds were selected from the last phase and then, placed on NaCl-free medium supplemented with 0.5 mg L-1 NAA and 1.0 mg L-1 BAP for rooting. All buds died when submitted to 120 mM NaCl. Plant regeneration was highly inhibited by all NaCl concentrations. On the other hand, concentrations from 20 to 80 mM NaCl increased bud number and length. Buds were selected from treatments with 80 and 100 mM NaCl, and 80 plants were regenerated in media without NaCl. Rooting was not affected by saline pre-treatment.

Efeito do estresse salino em genótipos tetraplóides de bananeira

This study evaluated 12 banana genotypes with respect to salt tolerance during initial growth, the most sensitive stage of the phenological cycle. Plants were grown for 21 days under 100 mM NaCl or under a control treatment without NaCl. Biometrical parameters and mineral contents in plant tissue were evaluated. Six genotypes (Calipso, FHIA-02, PA 42-44, Bucaneiro, FHIA-03 and PV 42-142) out of 12 considered in this study showed toxicity symptoms induced by saline treatment. The PA 42-44 genotype was pointed out as the most sensitive one because it showed the highest Na+ contents in both leaf blade and roots and rizome, besides a 18.5% reduction of dry matter production. The high Na+ contents found for PA 42-44 tissues suggest a low efficacy to extrude and to prevent the Na+ translocation to leaf blade. On the other hand, the Preciosa genotype showed both the lowest Na+ contents and the smallest reduction for dry matter production (0.2%) as well as a low Na+/K+ ratio indicating a salt tolerance strategy by Na+ extrusion.

Efeito do estresse salino e da prolina exógena em calos de milho

This work aimed at evaluating the effect of different NaCl concentrations (0, 68, 137 and 205 mM) in two maize (Zea mays L.) genotypes (W64Ao2 and Arizona 8601) callus cultures in N6 medium, supplemented or not with 6.0 mM proline. Treatments consisted of the combinations of the four NaCl levels with the two-proline levels under 4x2 factorial. Treatments were maintained for 60 days with subcultures at 20 days each. Relative growth rate, endogenous free putrescine, spermine, spermidine, proline and others amino acids were evaluated at the end of the experimental period. Proline addition improved callus growth in both genotypes in the control treatment and reduced deleterious effects in the highest salt level (250mM NaCl). W64Ao2 callus growth rate was higher than in the Arizona 8601 probably due, in part, to the higher proline accumulation and the maintenance of polyamine metabolism in those calluses.

RESPOSTA DE GENÓTIPOS DE MILHO AO ESTRESSE SALINO EM CONDIÇÕES HIDROPÔNICAS

Four maize (Zea mays L.) genotypes, Jatina C3 anao, BR-201, V-190 and LW-1, grown under hidroponic conditions, were evaluated for their tolerance to saline stress imposed by three salt levels (0, 50 and 100 mM NaCl). Plants submitted to 100 mM NaCl for 29 days had 50% lower dry matter production and 75% reduced leaf area, as compared to the control (0 mM NaCl) plants. Among the four genotypes studied, LW-1, a pure line, produced the least dry matter and leaf area. The increase salt levels in solution decreased the growth rate of both shoot and root in all genotypes. Roots had the largest sodium concentration and also showed the largest decrease in the relative growth rate, demonstrading the negative effect of sodium accumulation. The number and size of the stomata were not affected by saline stress.

Cultivo in vitro de ápices caulinares de abacaxizeiro para limpeza clonal em relação à fusariose

The object of this study was to find a nutricional means for the cultivation of the shoot tips of Perola pineapples, in order to free them of infections caused by Fusarium subglutinas. The first step was to remove healthy shoot tips from healthy crowns under aseptic conditions and inoculate nine different cultivation media with or whithout traces of BAP, GA3 and AIA. The levels of necrosis in the plants were studied after 30,45 and 60 days. Selected shoot tips removed from the plants contaminated with F. subglutinans were inoculated to check their viability as pathogen-free clones. The results revealed the influence of the cultivation media in the regeneration of plants and the viability of clonal cleansing of infected plants. It was also noted that 100% of the regenerated plants remained pathogen-free.

Hiperidricidade: uma desordem metabólica

The hyperhydricity, formerly called vitrification, is considered a physiological, biochemistry and morfologic disorder due to abnormal accumulation of water inside the cells and tissues. Plants grown in vitro are undoubtedly under continuous stress condition which results in metabolic changes characteristic of oxidative stress. Anatomically plants or shoots affected often become swollen, with pale green, translucent sheets, glass-like, low relative number of cells / cell area and hipolignification. Physiological changes occur in major metabolic pathways including photosynthesis, respiration and transpiration resulting in reduced efficiency of these metabolic pathways. Morphological, physiological and biochemical disorders are triggered by physical factors related to the environment of cultivation vessels and consistency of the culture medium or by chemical factors such as culture medium components, especially the growth regulators in high concentrations. The hyperhydricity occurs at various levels of severity, reaching result in irreversible loss of morphogenic capacity and the establishment of a state of neoplastic cells, however, in most cases hyperhydricity is considered reversible. This review focuses on the current knowledge about the phenomenon of hyperhydricity addressing morphological, physiological, biochemical, and reversibility of the process.