Annual growth rings in the mangrove Laguncularia racemosa (Combretaceae)

Stem discs from trees of known age were used to determine the periodic nature of the growth rings formed in Laguncularia racemosa and to describe the anatomical features of these rings. The growth rings were scarcely distinct on microscopic examination, but they were well distinguishable macroscopically, with alternating light brown and dark brown layers. Cross-dating analysis revealed the occurrence of annual growth rings in L. racemosa. The existence of annual growth rings in L. racemosa suggests that it may have great potential for dendrochronology and should encourage age-related studies on the dynamics of mangrove forests. These studies can be important for the evaluation of climate change impact on mangrove ecosystems, as well as for the analysis of effects related to climate variability on plant communities.

SAGE transcript profiling of the juvenile cambial region of Eucalyptus grandis

Despite the importance of Eucalyptus spp. in the pulp and paper industry, functional genomic approaches have only recently been applied to understand wood formation in this genus. We attempted to establish a global view of gene expression in the juvenile cambial region of Eucalyptus grandis Hill ex Maiden. The expression profile was obtained from serial analysis of gene expression (SAGE) library data produced from 3- and 6-year-old trees. Fourteen-base expressed sequence tags (ESTs) were searched against public Eucalyptus ESTs and annotated with GenBank. Altogether 43,304 tags were generated producing 3066 unigenes with three or more copies each, 445 with a putative identity, 215 with unknown function and 2406 without an EST match. The expression profile of the juvenile cambial region revealed the presence of highly frequent transcripts related to general metabolism and energy metabolism, cellular processes, transport, structural components and information pathways. We made a quantitative analysis of a large number of genes involved in the biosynthesis of cellulose, pectin, hemicellulose and lignin. Our findings provide insight into the expression of functionally related genes involved in juvenile wood formation in young fast-growing E. grandis trees.

Interaction between forest fragments and adjacent coffee and pasture agroecosystems: responses of the ant communities (Hymenoptera, Formicidae)

The responses of the ant community to environmental change, from forest fragment to agroecosystems (coffee or pasture) were evaluated in the south of the state of Minas Gerais, Brazil. In this paper we analized the interactions between forest and the two most typical agroecosystem from southest Brazil: sun-growing coffee plantation and introduced pasture. We sampled the ant community from five of each agroecosystems, inside the adjacent forest fragment, and on the edge between them. In each site we removed the litter from fifteen 1m(2) plots and extracted the ants using a Winkler extractor. A total of 165 ant species, distributed in 48 genera and 10 subfamilies were recorded. The coffee plantation presented the lowest abundance and estimated species richness. The causes of the changes observed among the areas are discussed.

Tree-ring formation, radial increment periodicity, and phenology of tree species from a seasonal semi-deciduous forest in southeast Brazil

Many tropical tree species produce growth rings in response to seasonal environmental factors that influence the activity of the vascular cambium. We applied the following methods to analyze the annual nature of treering formation of 24 tree species from a seasonal semi-deciduous forest of southeast Brazil: describing wood anatomy and phenology, counting tree rings after cambium markings, and using permanent dendrometer bands. After 7 years of systematic observations and measurements, we found the following: the trees lost their leaves during the dry season and grew new leaves at the end of the same season; trunk increment dynamics corresponded to seasonal changes in precipitation, with higher increment (active period) during the rainy season (October-April) and lower increment (dormant period) during the dry season (May-September); the number of tree rings formed after injuries to the cambium coincided with the number of years since the extraction of the wood samples. As a result of these observations, it was concluded that most study trees formed one growth ring per year. This suggests that tree species from the seasonal semi-deciduous forests of Brazil have an annual cycle of wood formation. Therefore, these trees have potential for use in future studies of tree age and radial growth rates, as well as to infer ecological and regional climatic conditions. These future studies can provide important information for the management and conservation of these endangered forests.

Sigatoka disease reduces the greenlife of bananas

Sigatoka disease (SD) of bananas is caused by the pathogenic fungus Mycosphaerella musicola Leach. This disease provokes necrotic lesions on leaves and serious infestations can lead to a substantial reduction in the leaf area of infected plants and thus to yield losses. In addition to these effects on yield, SO was found to have an impact on fruit quality, especially because exported bananas ripen prematurely. In the present work, a plantation survey and experiments have been conducted in Guadeloupe (FWI) to assess the effect of this disease on the greenlife of bananas harvested at a constant physiological age, as measured in degree-days (dd). Our results revealed that bananas harvested at 900 dd from plants with high Sigatoka disease severity had normal diameter growth, but a shorter greenlife (GL) than bananas harvested from uninfected plants. These results indicate that SD is directly responsible for the reduction of banana greenlife since the reduction of GL could not be attributed to the harvest of fruits at a more advanced physiological age (dd). Furthermore, a correlation was noted between SO severity and GL The potential physiological mechanisms involved are also discussed. (C) 2008 Elsevier Ltd. All rights reserved.