Alterações anatômicas no caule de plantas jovens de Eucalyptus grandis pelo ataque do psilídeo (Ctenarytaina spatulata TAYLOR, PSYLLIDAE, HEMIPTERA).

Dentre os insetos da família Psyllidae que atacam o eucalipto, estão os do gênero Ctenarytaina, de origem australiana, introduzidos em vários países, inclusive no Brasil. Estes insetos causam danos indiretos a planta, pela extração da seiva, injeção de substâncias tóxicas e transmissão de viroses. Os danos relacionados a madeira normalmente referem-se à deformação e quebra de fuste em plantas jovens em condições de campo. O objetivo desse trabalho foi descrever as alterações anatômicas no caule, resultantes do ataque de Ctenarytaina spatulata, através da observação microscópica de seções histológicas transversais do caule de plantas jovens de Eucalyptus grandis. Para isso, utilizou-se plantas infectadas pelo inseto e plantas testemunhas, cultivadas em casa de vegetação. Coletou-se amostras transversais compreendendo o ponto de inserção dos primeiros ramos e as áreas adjacentes próximas à base do caule das plantas. Obteve-se secções histológicas, em série, com espessura de 20-25 µm, coloridas em solução aquosa a 1% de safranina e azul de astra (safra-blau) e montou-se lâminas permanentes para análise microscópica. As plantas submetidas ao ataque do inseto apresentaram menor diâmetro do caule e formação de ramos muito próximos uns aos outros, devido ao encurtamento dos entrenós. Diferenças anatômicas quanto ao arranjo dos poros, presença de fibras gelatinosas, emissão de ramos laterais e crescimento secundário foram observadas, resultando na diminuição da resistência da madeira e tornando as plantas sob ataque de Ctenarytaina spatulata mais sujeitas a quebra.Resumo

Temperature and density of hot decaying 40Ca and 28Si

By means of quantum-fluctuation analysis techniques, temperatures and local partial densities of bosonic and fermionic fragments produced in the decay of hot 40Ca and 28Si projectile-like sources produced in mid-peripheral collisionsat sub-Fermi energies have been obtained. The used method treats bosonic and fermionic fragments differently. The purpose of such treatment is to trace important quantum effects such as fermion quenching or Bose-Einstein Condensation (BEC) in nuclei

Positive Selection Results in Frequent Reversible Amino Acid Replacements in the G Protein Gene of Human Respiratory Syncytial Virus

Human respiratory syncytial virus (HRSV) is the major cause of lower respiratory tract infections in children under 5 years of age and the elderly, causing annual disease outbreaks during the fall and winter. Multiple lineages of the HRSVA and HRSVB serotypes co-circulate within a single outbreak and display a strongly temporal pattern of genetic variation, with a replacement of dominant genotypes occurring during consecutive years. In the present study we utilized phylogenetic methods to detect and map sites subject to adaptive evolution in the G protein of HRSVA and HRSVB. A total of 29 and 23 amino acid sites were found to be putatively positively selected in HRSVA and HRSVB, respectively. Several of these sites defined genotypes and lineages within genotypes in both groups, and correlated well with epitopes previously described in group A. Remarkably, 18 of these positively selected tended to revert in time to a previous codon state, producing a “flip-flop” phylogenetic pattern. Such frequent evolutionary reversals in HRSV are indicative of a combination of frequent positive selection, reflecting the changing immune status of the human population, and a limited repertoire of functionally viable amino acids at specific amino acid sites

Molecular Epidemiology and Evolution of Human Respiratory Syncytial Virus and Human Metapneumovirus

Human respiratory syncytial virus (HRSV) and human metapneumovirus (HMPV) are ubiquitous respiratory pathogens of the Pneumovirinae subfamily of the Paramyxoviridae. Two major surface antigens are expressed by both viruses; the highly conserved fusion (F) protein, and the extremely diverse attachment (G) glycoprotein. Both viruses comprise two genetic groups, A and B. Circulation frequencies of the two genetic groups fluctuate for both viruses, giving rise to frequently observed switching of the predominantly circulating group. Nucleotide sequence data for the F and G gene regions of HRSV and HMPV variants from the UK, the Netherlands, Bangkok and data available from Genbank were used to identify clades of both viruses. Several contemporary circulating clades of HRSV and HMPV were identified by phylogenetic reconstructions. The molecular epidemiology and evolutionary dynamics of clades were modelled in parallel. Times of origin were determined and positively selected sites were identified. Sustained circulation of contemporary clades of both viruses for decades and their global dissemination demonstrated that switching of the predominant genetic group did not arise through the emergence of novel lineages each respiratory season, but through the fluctuating circulation frequencies of pre-existing lineages which undergo proliferative and eclipse phases. An abundance of sites were identified as positively selected within the G protein but not the F protein of both viruses. For HRSV, these were discordant with previously identified residues under selection, suggesting the virus can evade immune responses by generating diversity at multiple sites within linear epitopes. For both viruses, different sites were identified as positively selected between genetic groups

Climate seasonality limits leaf carbon assimilation and wood productivity in tropical forests

The seasonal climate drivers of the carbon cycle in tropical forests remain poorly known, although these forests account for more carbon assimilation and storage than any other terrestrial ecosystem. Based on a unique combination of seasonal pan-tropical data sets from 89 experimental sites (68 include aboveground wood productivity measurements and 35 litter productivity measurements), their associate canopy photosynthetic capacity (enhanced vegetation index, EVI) and climate, we ask how carbon assimilation and aboveground allocation are related to climate seasonality in tropical forests and how they interact in the seasonal carbon cycle. We found that canopy photosynthetic capacity seasonality responds positively to precipitation when rainfall is < 2000 mm.yr−1 (water-limited forests) and to radiation otherwise (light-limited forests); on the other hand, independent of climate limitations, wood productivity and litterfall are driven by seasonal variation in precipitation and evapotranspiration respectively. Consequently, light-limited forests present an asynchronism between canopy photosynthetic capacity and wood productivity. Precipitation first-order control indicates an overall decrease in tropical forest productivity in a drier climate.Peer reviewe

Climate seasonality limits leaf carbon assimilation and wood productivity in tropical forests

The seasonal climate drivers of the carbon cycle in tropical forests remain poorly known, although these forests account for more carbon assimilation and storage than any other terrestrial ecosystem. Based on a unique combination of seasonal pan-tropical data sets from 89 experimental sites (68 include aboveground wood productivity measurements and 35 litter productivity measurements), their associated canopy photosynthetic capacity (enhanced vegetation index, EVI) and climate, we ask how carbon assimilation and aboveground allocation are related to climate seasonality in tropical forests and how they interact in the seasonal carbon cycle. We found that canopy photosynthetic capacity seasonality responds positively to precipitation when rainfall is  < 2000 mm yr⁻¹ (water-limited forests) and to radiation otherwise (light-limited forests). On the other hand, independent of climate limitations, wood productivity and litterfall are driven by seasonal variation in precipitation and evapotranspiration, respectively. Consequently, light-limited forests present an asynchronism between canopy photosynthetic capacity and wood productivity. First-order control by precipitation likely indicates a decrease in tropical forest productivity in a drier climate in water-limited forest, and in current light-limited forest with future rainfall  < 2000 mm yr⁻¹

The Negative Effect of Lianas on Tree Growth Varies with Tree Species and Season

Lianas reduce tree growth, reproduction, and survival in tropical forests. Liana competition can be particularly intense in isolated forest fragments, where liana densities are high, and thus, host tree infestation is common. Furthermore, lianas appear to grow particularly well during seasonal drought, when they may compete particularly intensely with trees. Few studies, however, have experimentally quantified the seasonal effects of liana competition on multiple tree species in tropical forests. We used a liana removal experiment in a forest fragment in southeastern Brazil to test whether the effects of lianas on tree growth vary with season and tree species identity. We conducted monthly diameter measurements using dendrometer bands on 88 individuals of five tree species for 24 months. We found that lianas had a stronger negative effect on some tree species during the wet season compared to the dry season. Furthermore, lianas significantly reduced the diameter growth of two tree species but had no effect on the other three tree species. The strong negative effect of lianas on some trees, particularly during the wet season, indicates that the effect of lianas on trees varies both seasonally and with tree species identity

Estrutura fitossociológica em uma zona de ecóteno de Floresta Estacional Semidecidual e Floresta Ombrófila Mista.

O objetivo do estudo foi caracterizar a estrutura do estrato arbóreo/arbustivo e compreender a unidade fitogeográfica presente na área da Usina Hidroelétrica de Mauá, no médio rio Tibagi, Paraná