Antidiarrheal mechanism of Carpolobia lutea leaf fractions in rats

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Ventilation of the giant nests of Atta leaf-cutting ants: does underground circulating air enter the fungus chambers?

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Pineapple Leaf Fibers for Composites and Cellulose

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

PLANT-TO-SEED TRANSMISSION of CURTOBACTERIUM FLACCUMFACIENS pv. FLACCUMACIENS IN A DRY BEAN CULTIVAR

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Épocas de aplicação de nitrogênio para híbridos de mamona no sistema plantio direto em safrinha

The castor bean cultivation has a high demand for nitrogen, in addition, the efficiency of nitrogen fertilization in most cases is low, so that this essential nutrient is provided at the appropriate time. The objective was to study the time nitrogen application in castor bean hybrids under no-till system in off-season. The experiment was carried out in an experimental area located in Botucatu, São Paulo State, Brazil, for two growing off-seasons (2006 and 2007). The experimental design was a randomized block in split plot design, with four replications. The plots were constituted by two castor bean hybrids (Lyra/Savana in 2006 and Lyra/Sara in 2007). Six combination of times out rates (0-0, 0-100, 100-0, 30-70, 70-30, 50-50 kg ha-1 of N) side dressing nitrogen fertilization constituted the subplots. The N source used was ammonium nitrate, applied 20 days after emergence and 40 days after emergence. Measurements were carried out: dry matter production of shoots, nitrate and ammonium leaf, leaf analysis, yield components and nitrogen factor utilization. The highest grain yield was obtained to the hybrid Lyra with nitrogen fertilization. In 2006 the highest nitrogen utilization factor to the hybrid Lyra was obtained with the form 70-30 and in the 2007 with 50-50.

Expressed sequence tags from Atta laevigata and identification of candidate genes for the control of pest leaf-cutting ants.

Leafcutters are the highest evolved within Neotropical ants in the tribe Attini and model systems for studying caste formation, labor division and symbiosis with microorganisms. Some species of leafcutters are agricultural pests controlled by chemicals which affect other animals and accumulate in the environment. Aiming to provide genetic basis for the study of leafcutters and for the development of more specific and environmentally friendly methods for the control of pest leafcutters, we generated expressed sequence tag data from Atta laevigata, one of the pest ants with broad geographic distribution in South America. Results: The analysis of the expressed sequence tags allowed us to characterize 2,006 unique sequences in Atta laevigata. Sixteen of these genes had a high number of transcripts and are likely positively selected for high level of gene expression, being responsible for three basic biological functions: energy conservation through redox reactions in mitochondria; cytoskeleton and muscle structuring; regulation of gene expression and metabolism. Based on leafcutters lifestyle and reports of genes involved in key processes of other social insects, we identified 146 sequences potential targets for controlling pest leafcutters. The targets are responsible for antixenobiosis, development and longevity, immunity, resistance to pathogens, pheromone function, cell signaling, behavior, polysaccharide metabolism and arginine kynase activity. Conclusion: The generation and analysis of expressed sequence tags from Atta laevigata have provided important genetic basis for future studies on the biology of leaf-cutting ants and may contribute to the development of a more specific and environmentally friendly method for the control of agricultural pest leafcutters.

A pest is a pest is a pest? The dilemma of neotropical leaf-cutting ants: Keystone taxa of natural ecosystems

Leaf-cutting ants of the genera Acromyrmex and Atta are considered the principal polyphagous pests of the Neotropics. Although some members of these genera are of economic importance, have a broad geographic distribution, and are extremely good colonizers, others are endemic and closely interact with native ecosystems. Control is generally practiced against any colony, irrespective of its taxonomic status. Indiscriminate control coupled with habitat destruction threatens endemic species with extinction, and, through habitat simplification, favors other pest species. As nests of Atta are large, having several square meters of nest surface, the endemic taxa can be easily used as environmental indicators for natural ecosystems. Likewise, the pest species can be used to detect environmental disturbance. As these ants are keystone species and easily identified by nonspecialists, efforts should be made to integrate these into viable conservation programs.

Changes in sensitivity of the isolated guinea-pig vas deferens induced by a lyophilized Phoradendron latifolium leaf infusion

The effect of a lyophilized mistletoe infusion (LMI) was studied on isolated guinea-pig vas deferens. LMI caused a contraction which was partially blocked by phentolamine but not by atropine. LMI caused a shift to the left of the norepinephrine concentration-effect curve (CEC), an effect which appeared to be blocked by atropine and was absent in animals previously treated with reserpine and α-methyl-para-tyrosine. The increase of the norepinephrine maximal response induced by LMI was not blocked by atropine or pharmacological denervation. LMI caused a shift to the right of the acetylcholine CEC and had no effect on the acetylcholine maximal response. These results suggest that the effects seem to be due mainly to the presence of potassium ion in the LMI; however, the participation of muscarinic agonist(s) of reduced intrinsic activity or some tyramine-like substance could not be ruled out.

Cellulose degradation by Leucocoprinus gongylophorus, the fungus cultured by the leaf-cutting ant Atta sexdens rubropilosa

Leucocoprinus gongylophorus, the fungus cultured by the leaf-cutting ant Atta sexdens rubropilosa, is able to degrade efficiently cellulose, microcrystaline cellulose, carboximethylcellulose, and cellobiose. Analysis of the degradation products indicate that the fungus produce extracellular β-glucosidase, exo- and endo-glucanase. The importance of cellulose degradation to the association of fungus and ant is discussed.

Microbiological changes in the nests of leaf-cutting ants fed on sesame leaves

The number of bacteria and yeasts occurring in the organic matter inside the nests were determined both in colonies of leaf-cutting ants reared on Eucaliptus alba (control) or Sesamum indicum (experimental). Sesame leaves induce imbalance and nests usually die. In control nests the number of bacteria in newer sponge and in older sponge were similar (3.6 x 105 and 1.4 x 105 CFU/g, respectively) whereas in waste deposit the mean reached 7.3 x 107 CFU/g. The most Probable Number (MPN/g) of yeasts were 2.7 x 104, 1.3 x 105/g and 2.2 x 104 for newer sponge, older sponge and waste deposit, respectively. Using material from older sponge for comparison, the number of bacteria and yeasts reared on sesame leaves showed significant differences. The number of bacteria was 3.3 x 107 CFU/g, a value close to that found in waste deposit of normal (control) nests, whereas the number of yeasts was 6.7 x 105/g. These changes in microbial populations due to the effect of sesame leaf uptake could be a significant factor in nest imbalance and mortality when leaf-cutting ants are consuming toxic plants.

Produção de matéria seca de feijoeiros submetidos a diferentes níveis de magnésio em solução nutritiva

The effect of Mg levels in nutrient solution upon root, stem, leaf, fruit and total dry matter production of common bean (Phaseolus vulgaris L. cv. Carioca) was studied. Bean plants were grown in Hoagland & Arnon n. 2 solution modified to obtain 2.4, 24.3, 48.6, 72.9 and 97.2 ppm of Mg. The experimental design was a split-plot factorial replicated three times with five Mg levels and five samplings which were done fortnightly. Results were compared with those observed in plants submitted to a nutrient solution with 48.6 ppm of Mg concentration, considered the ideal Mg content. Only a mild prejudicial effect was observed with Mg excessive levels. Stem, leaves and total dry matter were higher when 2.4 ppm were used, suggesting this level as the concentration chosen for the culture of common bean.

Effect of constituents of the foliar wax of Didymopanax vinosum on the foraging activity of the leaf-cutting ant Atta sexdens rubropilosa

Leaf epicuticular waxes may affect substrate selection by leaf-cutting ants, and host recognition by several phytophagous insects. The influence of the crude epicuticular wax of Didymopanax vinosum E. March. (Araliaceae), and its major constituents lupeol and free primary alcohols, on substrate selection by the leaf-cutting ant Atta sexdens rubropilosa Forel, was investigated. Two ant colonies were used in laboratory bioassays. Corn flakes (zea) were impregnated with chloroform solutions of the substances being tested and fed to the adults. One of the colonies gave results, in most of the tests, not significantly different from the controls. The other colony, however, discriminated against the crude wax, a strong deterrent effect being observed from the first of a series of eight trials. The same colony was able to discriminate against lupeol after the second trial. The fraction of primary n-alcohols (22% C28, 66% C30 and 12% C32) deterred feeding only after the fifth trial. The results demonstrate that some constituents of epicuticular waxes may deter the foraging activity of A. sexdens rubropilosa, depending, however, on the colony under observation. It is suggested that lupeol, of the foliar wax of D. vinosum, is an important deterrent to leaf-cutting ants, although with less pronounced effects than those observed in tests with the crude wax.

Inhibitory effects of jackbean (Canavalia ensiformis L.) leaf residues on germination and vigour of crops and weeds

The effects of jackbean leaf residues incorporated in the soil on germination and seedlings growth of cucumber, radish and some weeds was examined. Trials were carried out under greenhouse conditions to (a) determine the amount of incorporated residue that is inhibitory to two test plants, (b) to determine if decomposition time changes the inhibitory levels of jackbean residues on test plants and (c) to determine the amount of residue that is inhibitory to the weed species. Jackbean leaf residues incorporated in soil at concentration of 2% or higher and allowed to decompose for a period of 0 to 2 weeks before sowing, reduced the initial growth of cucumber and radish and at different concentrations, reduced germination and growth of three weed species. These results suggest the presence of allelopathic components in Jackbean leaves that could affect seed germination and seedling development.

Virulência de isolados Dexanthomonas campestris pv. Phaseoli (Smith) dye em feijoeiro

The objective of this research was to evaluate de reaction of leaves and pods of five cultivars of bean (Phaseolus vulgaris L.) plants to twenty strains of Xanthomonas campestris pv. phaseoli. The strains were inoculated onto leaves in a greenhouse, and onto pods in a growth chamber. The results obtained were analyzed and the strains classified into three groups: low, medium, and high virulence. Most of the strains showed high virulence on leaves of Carioca and Rio Negro cultivars, as opposed to only low to medium virulence on leaves of IAPAR 14, IAPAR 16, and G. N. Nebraska # 1 sel. 27 cultivars. There were, however, individual strains powerful enough to overcome the leaf resistance of IAPAR 14, IAPAR 16, and G. N. Nebraska # 1 sel. 27. With regard to pods, most strains showed high virulence on all bean cultivars, with exception of IAPAR 14 where virulence was at medium level. A correlation between leaf and pod symptoms was found to exist in Carioca, Rio Negro, and IAPAR 14 cultivars. No such correlation was observed in IAPAR 16 and G. N. Nebraska # 1 sel. 27. Comparing strains producing melanine in vitro with those not producing this pigment, no difference was observed with regard to virulence.