Functional traits and water-transport strategies of woody species in an insular environment in a tropical forest.

PREMISE: Plants survive in habitats with limited resource availability and contrasting environments by responding to variation in environmental factors through morphophysiological traits related to species performance in different ecosystems. However, how different plant strategies influence the megadiversity of tropical species has remained a knowledge gap. METHODS: We analyzed variations in 27 morphophysiological traits of leaves and secondary xylem in Erythroxylum pulchrum and Tapirira guianensis, which have the highest absolute dominance in these physiognomies and occur together in areas of restinga and dense ombrophilous forest to infer water-transport strategies of Atlantic Forest woody plants. RESULTS: The two species presented different sets of morphophysiological traits, strategies to avoid embolism and ensure water transport, in different phytophysiognomies. Tapirira guianensis showed possible adaptations influenced by phytophysiognomy, while E. pulchrum showed less variation in the set of characteristics between different phytophysiognomies. CONCLUSIONS: Our results provide essential tools to understand how the environment can modulate morphofunctional traits and how each species adjusts differently to adapt to different phytophysiognomies. In this sense, the results for these species reveal new species-specific responses in the tropical forest. Such knowledge is a prerequisite to predict future development of the most vulnerable forests as climate changes.

Occurrence of annual growth rings in Rhizophora mangle in a region with low climate seasonality.

The formation of annual growth rings has been confirmed for several mangrove species in the last decade, among which is the Rhizophora mangle. However, the record of annual rings for this species was made in a region with high hydric seasonality, a widely recognized induction factor of annual rings in tropical species. In this sense, the present study aimed to verify the occurrence of annual growth rings in R. mangle in the mangroves of Guaratiba (Rio de Janeiro, Southeastern Brazil), a region with low hydric seasonality. For this purpose, the crossdating technique was applied in ten trees collected with known age (seven years). The growth rings are characterized by alternating layers of low vessel density (earlywood) and high vessel density (latewood). Multiple regression analysis indicated that growth rings width variation is driven by precipitation, water surplus, water deficit and water storage. Crossdating analysis confirmed the existence of annual growth rings in the R. mangle in Guaratiba. This discovery in a region with low hydric seasonality increases the dendrocronological potential of this species and suggests the importance of biological factors (eg. phenological behavior) as complementary inductors for the formation of growth rings in this species.

Studies on cambial activity: advances and challenges in the knowledge of growth dynamics of Brazilian woody species.

The lack of specific research on the sequence of events that determine plant growth from meristem until wood formation represents a gap in the knowledge of growth dynamics in woody species. In this work, we surveyed published studies concerning cambial activity of Brazilian native species aiming at allowing the comparison of applied methods and obtained results. The annual cambial seasonality was observed in all the investigated species. Nevertheless, we found high heterogeneity in the used methodologies. As a result from this analysis, our opinion points to the need for standardizing sampling protocols and for discussing the suitability of experimental designs. This will help to define with greater precision the factors that determine the radial growth in the different tropical ecosystems.

Wood anatomy of Mollinedia glabra (Spreng.) Perkins (Monimiaceae) in two Restinga Vegetation Formations at Rio das Ostras, RJ, Brazil.

This paper aimed to characterize the anatomical structure of the wood of specimens of Mollinedia glabra (Spreng.) Perkins growing in two contiguous formations of restinga vegetation at Praia Virgem, in the municipality of Rio das Ostras, RJ. Both the Open Palmae (OPS) and the Sandy Strip Closed Shrub (SSCS) formations are found in coastal regions that receive between 1,100 and 1,300 mm of rainfall per year. Sapwood samples were collected in both formations. Typical anatomical features for this species include: solitary vessels, radial multiples or clusters elements, that are circular to angular in outline, 5-15 barred scalariform perforation plates, wood parenchyma scanty, septate fiber-tracheids, and wide multiseriate rays with prismatic crystals. Statistical analyses indicated a significant increase in the frequency of vessel elements and an increase in fiber-tracheid diameters in OPS individuals. These characteristics are considered structural adaptations to increased water needs caused by a greater exposure to sunlight. Continuous pruning may be responsible for the tyloses observed in OPS plants. The greater lengths and higher frequencies of the rays in SSCS trees may be due to the greater diameters of their branches. Our results suggest that M. glabra develops structural adaptations to the restinga micro-environmental variations during its development.

Wood anatomy of Mollinedia glabra (Spreng.) Perkins (Monimiaceae) in two Restinga Vegetation Formations at Rio das Ostras, RJ, Brazil

This paper aimed to characterize the anatomical structure of the wood of specimens of Mollinedia glabra (Spreng.) Perkins growing in two contiguous formations of restinga vegetation at Praia Virgem, in the municipality of Rio das Ostras, RJ. Both the Open Palmae (OPS) and the Sandy Strip Closed Shrub (SSCS) formations are found in coastal regions that receive between 1,100 and 1,300 mm of rainfall per year. Sapwood samples were collected in both formations. Typical anatomical features for this species include: solitary vessels, radial multiples or clusters elements, that are circular to angular in outline, 5-15 barred scalarifor perforation plates, ood parenchya scanty, septate fiber-tracheids, and wide multiseriate rays with prismatic crystals. Statistical analyses indicated a significant increase in the frequency of vessel elements and an increase in fiber-tracheid diameters in OPS individuals. These characteristics are considered structural adaptations to increased water needs caused by a greater exposure to sunlight. Continuous pruning may be responsible for the tyloses observed in OPS plants. The greater lengths and higher frequencies of the rays in SSCS trees ay be due to the greater diaeters of their branches. ur results suggest that . glabra develops structural adaptations to the restinga micro-environmental variations during its development.

Este trabalho objetiva caracterizar a estrutura anatômica do lenho de Mollinedia glabra, ocorrente em duas formações vegetais contíguas na restinga da Praia Virgem, município de Rio das Ostras, RJ. Essas formações Arbustiva Aberta de Pal-mae (AAP) e Arbustiva Fechada do Cordão Arenoso (AFCA) estão sobre cordão arenoso e recebem precipitações anuais de 1.100-1.300 mm. Foram obtidas amostras do lenho das duas forações. São características anatôicas gerais da espécie: elementos de vasos solitários, em arranjos radiais ou cachos, de seção de circular a angular; placa de perfuração es-calariforme, com 5-15 barras; parênquima axial escasso; fibro-traqueídes septadas e raios multisseriados largos, com cristais prismáticos. A análise estatística evidenciou aumento significativo na frequência dos elementos de vasos e aumento no diâmetro das fibrotraqueídes nos indivíduos de AAP. Essas características são consideradas adaptações estruturais ao aumento da necessidade de água causada por maior exposição à luz solar. A realização de podas frequentes pode ter relação com a formação de tilos nesses indivíduos. O aumento significativo no comprimento e frequência de raios podem representar uma resposta ao maior diâmetro dos indivíduos em AFCA. Os resultados obtidos sugerem que M. glabra desenvolve adaptações estruturais às variações micro-ambientais da restinga durante seu desenvolvimento.