The anatomical features of growth rings of 13 representative species of the swamp forests within the Atlantic rain forest of the State of Rio de Janeiro, southeastern Brazil, were studied. Most species showed distinct rings. The growth ring boundaries were marked by fibrous zones frequently associated with marginal parenchyma bands, and growth ring boundary features were characteristic of the particular families and genera analysed. Leaf fall can be related to the occurrence of growth rings in seven species, whereas in evergreen species growth rings can be related to flooding. In Euphorbiaceae species, flooding regime differences (periodical or permanent) are related to the shape and distribution of new cells produced by the cambium and, thus, growth ring structure.

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This paper reviews histological studies of cambium activity in South American woody species and provides future research prospects. The majority of the studies almost exclusively describe radial increment and/or its periodicity. There are 15 papers concerning the cambial activity of 17 woody species from the South American flora and 3 exotic species in 4 countries that were published to date. Despite endogenous factors affecting the radial meristem, the seasonality of rains has been identified as the main factor influencing cambial activity in the tropics and subtropics. There is a lack of standardization and a need for improvement and discussion concerning the methods used. Moreover, radial growth studies conducted by monitoring cambium cell production are still scarce in South America, especially when considering the high diversity of the continent’s flora and ecosystems.

The regeneration patterns of shoot apices derived from in vitro plants of four varieties of sugar cane in response to different growth regulators and light were evaluated. The cellular origin of the regeneration processes was also investigated. Explants cultivated on medium supplemented with NAA and incubated under light showed direct bud regeneration from cells of external layers of the ground parenchyma of the stem. Explants cultivated in the dark on medium supplemented with low concentrations of picloram (PIC) or 2,4D (4.0 and 4.5 mM, respectively) showed callus formation derived from the ground parenchyma of stem and development of preembryogenic masses derived from bundle sheath cells facing the phloem tissue of immature leaves. Somatic embryos at further developmental stages were visible following transfer to medium devoid of growth regulators and incubation under light. When incubated under light since the begining of the experiment, explants cultivated in the presence of higher PIC or 2,4D concentrations (40 and 22.6 mM, respectively) first displayed direct organogenesis from external layers of the ground parenchyma of the stem, followed by the development of organogenic calluses. Preembryogenic masses were also observed from bundle sheath cells of immature leaves. However, in contrast to the cultures pre-incubated in darkness for 30 days, the subsequent stages of embryo development were not detected. The regeneration efficiency of calluses induced by 2,4D and PIC was generally increased following desiccation in laminar flow or incubation on medium solidified with phytagel.

RESUMO O trabalho propõe a utilização dos caracteres anatômicos da madeira na interpretação da estrutura da comunidade arbórea da Reserva Biológica de Poço das Antas, RJ, Brasil (22º30' e 22º33'S e 42º15' e 42º19'W). Foram analisadas 26 espécies de 14 famílias, totalizando 72 espécimens. A alta incidência de características anatômicas comuns - camadas de crescimento distintas, porosidade difusa, placas de perfuração simples, fibras de paredes delgadas a espessas, raios com freqüência de 4 a 12/mm', com 1-3 células de largura, - foi corroborada pelas análises estatísticas, o que sugere a ocorrência de um padrão anatômico. Os resultados descritos se enquadram nas tendências ecológicas para espécies de planícies tropicais, que se caracterizam por uma menor freqüência de elementos de vaso mais largos e com placas de perfuração simples. Tais caracteres propiciam o transporte de grandes volumes de água por unidade de tempo e área transversal da madeira.

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.

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This paper describes a protocol for the efficient vegetative propagation of