Federal University of Roraima

About: Federal University of Roraima is a based out in . It is known for research contribution in the topics: Population & Thermogravimetry. The organization has 981 authors who have published 1218 publications receiving 7849 citations. The organization is also known as: Federal University of Roraima.

Outer cell wall structure and the secretion mechanism of colleters of Bathysa nicholsonii K. Schum. (Rubiaceae)

Abstract: Secretory structures are formed by many types of plants and are present on numerous different organs. Among the many types of known secretory structures, colleters are predominant on plants of the Rubiaceae. One remarkable characteristic of secretory tissues is the export of exudates; however, the precise mechanism involved in this process is still unclear. To better understand the mechanisms of exudate externalization it is necessary to understand the ultrastructure and dynamics of the outer cell wall of the secretory structures during the secretory process, and so we investigated these aspects of the colleters of Bathysa nicholsonii. The outer cell wall (OCW) exhibits multiple layers: a basal polysaccharide rich layer; a cuticular membrane, which is subdivided into arborescent and reticulated layers; and a thin cuticle proper. The structural organization of the OCW is changed during secretion passage, which is mainly related to the development of a secretion accumulation site on the polysaccharide rich layer. Secretion dynamics is driven by the organization and disruption of the secretion accumulation site. The results show that the OCW of the colleters of B. nicholsonii is a dynamic structure with an active role in secretion externalization via constant structural reorganization directly related to secretion passage.

Life table parameters of the red palm mite Raoiella indica (Acari: Tenuipalpidae) at various temperatures and for sexual and asexual reproduction

Abstract: The red palm mite, Raoiella indica Hirst, is a threat to coconut, banana and native Arecaceae and Heliconiaceae in Brazil. This mite originated in the Eastern Hemisphere and was first reported in 2004 in the Americas, where the pest is spreading quickly and causing severe damage to its host plants. The objective of this work was to determine the life-history parameters of R. indica at constant temperatures, estimate its thermal requirements [threshold temperature (Tb) and thermal constant (K)] and also compare its life table parameters between sexual reproduction and parthenogenesis. The life tables were constructed on leaflets of Adonidia merrillii at 15, 20, 24, 27, 30 and 34 °C and 65% RH and a 12-h photoperiod. The longevity and the number of laid eggs of non-copulated adult females were evaluated at 27 °C. Raoiella indica had complete development, from egg to adult, only at 20, 24, 27 and 30 °C. At 15 °C, the eggs did not hatch, and at 34 °C, the mites survived only until the larval stage. For sexual reproduction, the optimal temperature was 27 °C, under which the reproductive parameters were higher. The reproductive parameters for sexual reproduction were higher than those for parthenogenesis. The Tb was 14.79 °C, and the thermal constant was 208.33 degree days. The life parameters estimated in this study can be used for modelling and predicting the population growth of R. indica in the field and consequently for improving their management strategies.

Scheffersomyces stambukii f.a., sp. nov., a d-xylose-fermenting species isolated from rotting wood.

Abstract: Two isolates representing a new species of Scheffersomyces were isolated from rotting wood samples collected in an Amazonian forest ecosystem in Brazil. Analysis of the sequences of the D1/D2 domains showed that this new species is phylogenetically related to Scheffersomyces NYMU 15730, a species without a formal description, and the two are in an early emerging position with respect to the xylose-fermenting subclade containing Scheffersomyces titanus and Scheffersomyces stipitis. Phylogenomic analyses using 474 orthologous genes placed the new species in an intermediary position between Scheffersomyces species and the larger genus Spathaspora and the Candida albicans/Lodderomyces clade. The novel species, Scheffersomyces stambukii f.a., sp. nov., is proposed to accommodate these isolates. The type strain of Scheffersomyces stambukii sp. nov. is UFMG-CM-Y427T (=CBS 14217T). The MycoBank number is MB 824093. In addition, we studied the xylose metabolism of this new species.

Produção, qualidade dos frutos e teores de nitrogênio foliar em maracujazeiro-amarelo sob adubação nitrogenada

Abstract: Objetivou-se avaliar a adubacao nitrogenada sobre a producao, qualidade dos frutos e nitrogenio foliar de maracujazeiro-amarelo. O experimento foi realizado no Câmpus da Universidade Estadual de Mato Grosso do Sul – Aquidauana. O delineamento experimental utilizado foi o inteiramente casualizado, em parcelas subdivididas. As parcelas corresponderam as doses de N (0, 70, 140 e 210 kg ha -1 ano -1 de N), enquanto nas subparcelas, os meses de colheita (1; 2; 3; 4; 5 e 6 meses). As variaveis estudadas foram produtividade (PROD) (t ha -1 ); numero de frutos por planta (NFP); numero total de frutos (NTF); numero de frutos para consumo in natura (NFN) e numero de frutos para o consumo industrial (NFI), por hectare; massa (MF), comprimento (CF) e diâmetro dos frutos (DF); espessura da casca (ESC); rendimento de polpa (REP) e suco (RES); concentracao de solidos soluveis (SS); acidez titulavel (AT); e relacao SS/AT; e teores de N foliar (Nfol), no primeiro ano de cultivo. A producao concentrou-se principalmente no quarto mes (junho), o incremento de N no solo influenciou na massa media do fruto (175,7 g), notadamente com a adicao de 86 kg ha -1 de N; o comprimento dos frutos e os teores de N foliar aumentaram linearmente, ate 91,6 mm e 40,49 g kg -1 , respectivamente. Considerando a qualidade do fruto, na primeira safra de maracujazeiro-amarelo, nas condicoes de Aquidauana, recomendam-se 86 kg ha -1 ano -1 de N.