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.

-(Production of essential oils in plants of Mentha x piperita L. var. piperita (Lamiaceae) submitted to different light levels and nutrition of the substratum). Mentha x piperita L. var. piperita (mint pepper) is utilized due to the presence of essential oils, mainly because of the component menthol produced in glandular trichomes. The influence of light intensity and substratum fertility was evaluated on the amount produced and quality of the essential oil. The light intensities utilized were 100%, 70% and 50% of the total solar light and two levels of nutrition of the substratum were applied (forest soil and forest soil with addition of organic fertilizer. The high light intensity and the addition of fertilizer favored the growth in biomass, influencing in this sense the production of the essential oil per plant. The light intensity and the addition of fertilizer influenced the oil quality, showing the plants under full sun light and fertilization with higher menthol content than plants in shadow or without fertilization. Menthol was the major component of the essential oil.Key words -essential oils, growth, light intensity, organic fertilizer RESUMO -(Produção de óleos essenciais em plantas de Mentha x piperita L. var. piperita (Lamiaceae) submetidas a diferentes níveis de luz e nutrição do substrato). Mentha x piperita L. var. piperita (hortelã-pimenta) é bastante utilizada devido à presença de óleos essenciais, principalmente pelo componente mentol, produzidos nos tricomas glandulares. Foi avaliada a influência da intensidade de luz e da adubação do substrato na quantidade e qualidade do óleo essencial. As intensidades de luz utilizadas foram 100%, 70% e 50% da luz solar total e dois níveis de nutrição do substrato aplicados, solo de mata e solo de mata com adição de adubo orgânico. A alta intensidade de luz e a adubação favoreceram o crescimento em biomassa, influenciando no rendimento do óleo essencial por planta. A intensidade de luz e a adubação influenciaram na qualidade do óleo essencial, apresentando as plantas sob luz solar plena e adubadas apresentaram maior concentração relativa de mentol que plantas sombreadas ou sem adubo. O mentol foi o componente majoritário encontrado no óleo essencial.Palavras-chave -adubação, crescimento, intensidade de luz, óleos essenciais 1.Parte da dissertação de mestrado do primeiro autor, Programa de

RESUMO -(Morfoanatomia foliar da reófita Raulinoa echinata R. S. Cowan -Rutaceae). Reófitas são espécies vegetais confinadas aos leitos de rios e riachos de fortes corredeiras, crescendo acima do nível das inundações, mas não além do alcance da ocorrência regular das rápidas enchentes. A morfoanatomia foliar de Raulinoa echinata R.S.Cowan (Rutaceae) foi investigada objetivando compreender a adaptação às peculiaridades do hábitat reofítico. As folhas de R. echinata são dorsiventrais e hipoestomáticas. A epiderme é uniestratificada e os estômatos são anomocíticos. As células-guarda estão dispostas acima do nível das demais células epidérmicas (característica hidromórfica), mas com átrio externo conspícuo (característica xeromórfica). Aspectos mais marcantes relacionados ao hábitat reofítico são estenofilia e presença de suberina nas paredes periclinais internas das células epidérmicas. A área foliar varia com a intensidade de exposição ao sol, a densidade estomática varia com o fluxo do rio; as espessuras dos tecidos do mesofilo variam com ambas condições. Ductos secretores e idioblastos com cristais de fosfato de cálcio ocorrem no mesofilo. Os dados revelaram plasticidade da estrutura foliar às condições peculiares do ambiente reofítico e as condições sombreadas ou expostas ao sol. Palavras-chave: reófitas, Raulinoa echinata, características adaptativas, anatomia, folhaABSTRACT -(Leaf morphoanatomy of the rheophyte Raulinoa echinata R. S. Cowan -Rutaceae). Rheophytes are plants confined to the beds of swift-running streams and rivers, growing above flood level but not beyond the normal reach of flash floods. Leaf morphoanatomy of the rheophyte Raulinoa echinata R.S.Cowan (Rutaceae) was investigated with a focus on understanding adaptation to the peculiarities of the rheophytic habitat. R. echinata leaves are dorsiventral and hypostomatic. The epidermis has a single layer of cells and the stomata are anomocytic. The guard cells rise above the level of the other epidermal cells (a hydromorphic characteristic), but with a conspicuous outer cavity (a xeromorphic characteristic). Prominent traits related to the rheophytic habitat are stenophylls and the presence of suberin on the inner periclinal walls of the epidermal cells. Leaf area varies with sun exposure while stomatal density varies with river flow. In R. echinata, mesophyll tissue thickness varies with light intensity and river flow. Secretory cavities and idioblasts with calcium phosphate crystals occur in the mesophyll. The data revealed leaf-structure plasticity in relation to the singular conditions of the rheophytic environment as well as to shade or sunlight.Key words: rheophytes, Raulinoa echinata, adaptative characteristics, anatomy, leaf IntroduçãoAs reófitas constituem um grupo particular de vegetação ribeirinha. Diversas famílias têm espécies reófitas (Van Steenis 1981;1987) e, para a região Sul do Brasil, Klein (1979) relaciona 21 famílias, das quais Euphorbiaceae, Leguminosae e Myrtaceae são as mais representativas. O termo reófita foi empregado, ...

It is found totally or partially exposed to solar radiation and in different life forms -terricolous, rupicolous and epiphytes. The aim of this work was to compare morphoanatomical leaf characteristics of A. lindenii var. lindenii in distinct environmental conditions. On Santa Catarina Island (Florianópolis, SC), the following were collected: leaves of terricolous plants in the herbaceous restinga (high solar radiation), rupicolous from rocky coast (high solar radiation), terricolous and understory epiphytes (low solar radiation) in the arboreal restinga and understory rupicolous (low solar radiation) from hillside Atlantic rain forest. We measured length, breadth and area of leaf blade and sheath, stomatal density, length and breadth of guard-cells; width of leaf blade and structural components. Qualitative anatomical characteristics are similar in the distinct conditions analyzed. Low solar radiation determined greater expansion of the leaf area, due to stretching of the blade. Leaf blade and sheath have greater breadth under high solar radiation. Stomatal density was greater in leaves of plants in high solar radiation. Total blade leaf width was smaller in leaves of terricolous plants under high solar radiation, nevertheless, statistically significant differences were not found among other conditions.

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RESUMOReófitas são espécies de plantas que na natureza estão confinadas a leitos de córregos e rios encachoeirados, ao alcance de inundações bruscas regulares. 81 ABSTRACTRheophytes are species of plants that occur in the nature exclusiveiy beside swift-running streams and rivers which experience frequent and sudden floods. This study relate the morphoanatomical characteristics of the Dyckia brevifolia Baker and D. distachya Hassler two species of rheophytes bromeliad that occur at south Brazil. The roots of the two species are similar anatomicaly and they are constituted by ring tissue, cortex and central cylinder. The one-Iayer epidermis with root-hairs further covering. The cortex is constituted by outer parenchyma, sclerenchymatic ring, inner parenchyma and endodermis. The number of.exodermis layers is distinct among these species, it is higher in D. distachya. At the general way, the features find out in the adventiceus roots of D. brevifolia and D. distachya are similar at the others Bromeliaceae species. However, such characteristics must to favor the establishment and survival of these species in the rheophytic environment.

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.

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