Physical dormancy refers to seeds that are water impermeable. Within the Fabaceae, the structure associated with the breaking of dormancy is usually the lens. This study verified the role of the lens in physical dormancy of seeds of Schizolobium parahyba, a gap species of Fabaceae from the Atlantic Forest of Brazil. The lens in S. parahyba seeds appeared as a subtle depression near the hilum and opposite the micropyle. After treatment of the seeds with hot water, the lens detached from the coat. Blocking water from contacting the lens inhibited water absorption in hot-water-treated seeds. High constant (30°C) and alternating (20/30°C) temperatures promoted the breaking of physical dormancy and germination in non-scarified seeds. Maximum percentage of germination occurred earlier for seeds incubated at 20/30°C than for those incubated at 30°C. Seeds with a blocked lens did not germinate at alternating or high temperatures. This study suggests that alternating temperatures are probably the cause of physical dormancy break of seeds of S. parahyba in gaps in the forest.

So far data in the literature indicate that (1) the relative proportion of tropical species with dormant versus non-dormant seeds tends to increase with a decrease in temperature and precipitation, (2) in rain forests, more species with non-dormant seeds have been found, (3) in rain forests, physiological dormancy is normally the most common type of seed dormancy, (4) the reasons why rain forests have species with dormant seeds are not well known, and studies have been done to determine if there is a relationship between the presence of dormancy in seeds with seed characteristics and environmental conditions of rain forests, and (5) it has been suggested that seed dormancy type could be connected to seed dispersion. The purpose of this work was to test, by compiling data from the literature for 162 woody species from the Atlantic Rain Forest of Brazil, the proportion of species with non-dormant and dormant seeds, and to determine if dormancy and the classes of dormancy of these species are associated with plant successional status, light environment, seed mass, and seed dispersal. The results found were (1) approximately 60 % of species had non-dormant seeds, and 40 % of species had dormant seeds, (2) physical and physiological dormancies were present in similar proportions, and combinational dormancy was the least common class of dormancy, (3) it was found that the chance that a species has physical or physiological dormancy doubles if it is a species found in a sunny environment, (4) a relationship between seed dormancy and non-dormancy, and the successional group of the species, was not found, (5) physical dormancy was highest in the non-climax group, and physiological dormancy occurred in similar proportions in non-climax and climax groups; however, a relationship was not found between class of succession and class of dormancy, (6) the proportion of the dispersal classes shows predominance for zoochory, followed by anemochory and autochory, (7) a multiple logistic regression analysis suggests that if the seeds are spread by autochory, then the chance that the seeds have physical dormancy is about eight times greater, and (8) seed mass was not associated with the presence or absence of dormancy; however, the species with physiological dormancy had seeds with smaller masses than those with physically dormant seeds. In short, for the Atlantic Rain Forest, based in compiled data from literature, it was found that seed dormancy type was related with sunny environments, dispersion, and seed size.

Resumo A introdução e manejo de plântulas de Euterpe edulis Mart. em florestas tem sido uma alternativa encontrada para não levar a espécie à extinção devido ao extrativismo desenfreado. O objetivo deste estudo é ampliar o conhecimento das exigências ecológicas das plântulas desta espécie, visando auxiliar sua conservação in situ. Frutos despolpados da espécie germinaram em casa de vegetação e as plântulas, ainda com os vestigios da semente ligados ao eixo embrionário, foram separadas em seis lotes. Cada lote recebeu os seguintes tratamentos: 2% de luminosidade, 50% de luminosidade, sem nutrição mineral, com nutrição mineral, irrigação a cada dois dias e irrigação a cada sete dias. Observou-se que o tempo de esgotamento das reservas das sementes não pareceu ser influenciado pela intensidade de luz e fertilidade do solo, como também o peso da matéria seca, área foliar e número de folhas das plântulas, sugerindo que o crescimento da plântula parece ser independente da intensidade de luz e fertilidade do solo enquanto há reservas na semente. Sob regime de menor disponibilidade de água, as plântulas apresentaram aumento no teor de prolina da folha, indicando que a espécie apresenta regulação osmótica As plântulas apresentaram inibição do crescimento a 2% de luz solar, indicando que o nível de luz solar que chega ao interior da floresta fechada pode ser limitante para o crescimento de plântulas desta espécie.

Some species of Dyckia Schult. f., including Dyckia brevifolia Baker, are rheophytes that live in the fast-moving water currents of streams and rivers which are subject to frequent flooding, but also period of low water. This study aimed to analyze the leaf epidermis of D. brevifolia in the context of epidermal adaptation to this aquatic plant's rheophytic habitat. The epidermis is uniseriate, and the cuticle is thickened. The inner periclinal and anticlinal walls of the epidermal cells are thickened and lignified. Stomata are tetracytic, located in the depressions in relation to the surrounding epidermal cells, and covered by peltate trichomes. While the epidermal characteristics of D. brevifolia are similar to those of Bromeliaceae species, this species has made particular adaptations of leaf epidermis in response to its rheophytic environment.

Estudos anatômicos e de ontogênese da abscisão foliar em pomáceas são escassos. A queda foliar promovida após formada a zona de abscisão é um processo natural nas pomáceas, e prolonga-se durante o outono, até que ocorram as primeiras geadas no Sul do Brasil. Ainda não se conhece até quando as folhas de macieiras permanecem funcionais. O objetivo deste trabalho foi desenvolver uma metodologia que permita estudar o início e o fim das zonas de abscisão foliar de macieiras. O trabalho foi realizado nas cultivares 'Galaxy' e 'Fuji' em pomares comerciais de macieira, de Vacaria, Rio Grande do Sul. O método proposto consistiu em coletar,ramos do ano, com 10cm a 20cm de comprimento, e utilizar um segmento contendo uma parte do caule, uma gema axilar e a base do pecíolo, descartando a parte das quatro folhas do ápice. Os segmentos foram fixados, seccionados e corados para a observação da zona de abscisão em microscopia óptica. Os resultados mostraram que a metodologia utilizada permitiu descrever a zona de abscisão em macieiras e que ela é formada por células alongadas com parede celular delgada, apresentando lignificação junto à parede celular. O processo manteve a gema intacta e ocorreu no sentido adaxial para o abaxial. A abscisão foliar natural, em plantas de Galaxy e Fuji em sintomas de doença e em condições ambientais favoráveis, pode ser acompanhada 7 e 14 dias antes e depois da colheita, e após, com intervalos de 14 e 21 dias até maio. A partir de maio, as coletas devem ser feitas semanalmente. Essas informações serão úteis na tomada de decisão para realizar práticas culturais e/ou de controle químico, para a manutenção das folhas sadias, resultando no maior acúmulo de reservas de carboidratos e/ou redução do número de aplicações de fungicidas.

The studies about water status for woody plants of the Atlantic rain forest are negligence, despite its altitudinal gradient which reflect in five topographic formations with different water availability and the poor conservation status of this biome and high level of habitat fragmentation that demands a deeper scientific knowledge regarding species response to environmental heterogeneity. Seedlings of Hedyosmum brasiliense Mart. ex Miq., present at all altitudinal gradient of Atlantic rain forest were submitted to water stress and the results indicated that the species presents strategy that provides delay of tissue dissection through the adoption of mechanisms that can promote higher water absorption and retention with possibly aids its altitudinal distribution in Atlantic rain forest. These mechanisms were the increase of the root length, stomatal density, epidermis and palisade parenchyma thickness, root xylem arches; the higher distribution of carbon to root related to the shoot; the decrease of the leaf area, LAR, stomatal aperture, stomatal size, intercellular spaces and the presence of osmotic adjustment through the increase in the proline content.

Nodule cultures are formed through an intermediate morphogenetic route that lies between organogenesis and somatic embryogenesis. Although well described in many species, different aspects of the morphological and histological development of nodules remain to be clarified. Based on their threatened status and high ornamental value, Billbergia alfonsi-joannis and Billbergia zebrina, two epiphytic bromeliad species endemic to the South American Atlantic Forest, were studied. Nodular cultures were induced to grow from nodal segments taken from etiolated seedlings grown in vitro for 12 weeks in the dark on MS medium supplemented with 1 μM TDZ. Samples were taken for analysis weekly over 8 weeks of growth and analyzed under light, transmission electron, and scanning electron microscopes. Morphological and histological analysis showed that nodular clusters originated from stem pericycles and consisted of a polycenter, cambial tissue, cortical parenchyma, and a covering tissue. The polycenter consisted of an organizational center dispersed in parenchymal tissue. Each organizational center was formed by a vascular system surrounded by a bundle sheath. A cambial tissue surrounded these polycenters, promoting the regeneration of new nodules and leading to the formation of buds and roots. Primary nodules could generate secondary nodules in a repetitive process. Thus, histological analysis revealed the origin and formation of nodular cultures. These new data will support the establishment of micropropagation protocols and regeneration on a large scale for these species.

Plant growth-promoting rhizobacteria (PGPR) are considered to have a beneficial effect on host plants. Azospirillum brasilense is a diazotroph associated with important agricultural crops such as maize and wheat, and has been used as model organism to investigate associative plant growth promotion. In this study, we have employed scanning electronic microscopic to observe the presence of bacterium on the root surface. Two-dimensional gel electrophoresis and mass spectrometry were used to analyze the changes in protein profile of maize roots in response to A. brasilense strain FP2 7 days after inoculation and we observed 46 differently expressed protein spots. We report the identification of three of these proteins.