This difference might reflect the older age of the northern mangroves, which likely remained stable during the Quaternary glaciations. The lowest variability observed in the southern populations of the red mangrove most likely reflects their recent age, associated with allelic reduction, resulting from the consecutive founder events that followed subsequent colonization of estuaries during the gradual warming by the end of the last glacial period.
-(Comparison of leaf morphology of tree species from three distinct successional stages of tropical rain forest (Atlantic Forest) in Southern Brazil). We investigated the leaf morphology of trees from three distinct successional stages (early, intermediate, late) of a lowland rain forest located near the coast of Paraná State, Brazil. This forest grows on sandy soil with low nutrient content. Leaves from trees from the early successional stage present a higher degree of sclerophylly, having thicker leaves, smaller leaf area, higher stomata density, thicker palisade parenchyma, and higher prevalence of sclerenchyma than those of species from the intermediate and late successional stages. Variation of leaf morphology along the successional gradient is likely related to microclimatic changes and the interaction of plant-soil processes, which intensify in older successional stages.Key words -Atlantic Forest, leaf morphology, sclerophylly, succession RESUMO -(Comparação da morfologia foliar de espécies arbóreas de três estádios sucessionais distintos de floresta ombrófila densa (Floresta Atlântica) no Sul do Brasil). A morfologia foliar de espécies arbóreas foi investigada em três estádios sucessionais distintos (inicial, intermediário e avançado) de uma floresta ombrófila densa das terras baixas, no litoral do Estado do Paraná, crescendo sobre solo arenoso e oligotrófico. As espécies do estádio inicial apresentaram maior grau de escleromorfismo, com folhas mais espessas, menores em área, maior densidade estomática, maior espessura do parênquima paliçádico e maior incidência de espécies com tecido esclerenquimático em comparação com as espécies dos demais estádios sucessionais (intermediário e avançado). As variações na morfologia foliar ao longo do gradiente sucessional são relacionadas às mudanças microclimáticas e aos processos de interação planta-horizontes orgânicos do solo que se intensificam nos estádios mais avançados.Palavras-chave -Esclerofilia, Floresta Atlântica, morfologia foliar, sucessão IntroduçãoVários estudos mostram que as plantas que crescem em solos arenosos, com baixa retenção de água e de nutrientes, possuem folhas com características xeromórficas, mesmo que pertençam a ambientes de florestas tropicais (Turner et al. 1995, Medina et al. 1990, Cao 2000. Algumas dessas formações vegetais, como por exemplo restinga e campinarana, possuem plantas com folhas espessas, textura coriácea, cutícula, hipoderme, parênquima paliçádico e esclerênquima bem desenvolvidos. Essas características xeromórficas são consideradas vantajosas para as plantas, nessas áreas, pois reduzem a perda de água, o excesso de luz e a ação dos herbívoros. Baseadas nas características morfológicas e nos baixos teores de fósforo e nitrogênio foliares, muitas dessas formações vegetais foram classificadas como esclerófilas. Apesar da controvérsia sobre o termo esclerofilia, que no senso estrito significa "folhas duras" (Roth 1984), o conceito mais aceito (ou pelo menos mais utilizado) é aquele que relaciona plantas esclerófi...
-(Richness, structure, and edaphic interactions in the restinga gradient of Parque Estadual do Acaraí, Santa Catarina State, Brazil). The present work characterized the flora and phytocommunities of a restinga gradient on the coast plain of Santa Catarina State and correlated them to edaphic attributes. The floristic survey followed the wide patrolling method and the community structure was determined through the plot method. Soil samples of each physiognomy were collected for analysis of macronutrients, organic matter, moisture, and litter thickness. Flora comprises 319 species, 244 of which occur exclusively in formations of herbaceous restinga (63), shrub restinga (32), shrub-tree restinga (46), and transition forest (103). The structural pattern of each restinga physiognomy studied was influenced by edaphic factors as organic matter, potassium, and aluminum contents, cation exchange capacity, and litter thickness. These attributes are determinant for the flora characterizing each phytocommunity.
Coffee plants were subjected to heat stress (37 °C) and compared with control plants (24 °C). Cell wall polysaccharides were extracted using water (W), EDTA (E) and 4M NaOH (H30 and H70). In addition, monolignols were analyzed, and the leaves were observed by microscopy. Plants under heat stress accumulated higher contents of arabinose and galactose in fraction W. Xylose contents were observed to decrease in H30 fractions after the heat stress, whereas galactose and uronic acid increased. H70 fractions from plants exposed to heat stress showed increased xylose contents, whereas the contents of arabinose and glucose decreased. Differences in the molar-mass profiles of polysaccharides were also observed. The primary monolignol contents increased after the heat stress. Structural alterations in palisade cells and ultrastructural damage in chloroplasts were also observed. Our results demonstrate that the chemical profile of coffee cell-wall polymers and structural cell anatomy change under heat stress.
Arabidopsis thaliana grown in a light regime that included ultraviolet-B (UV-B) radiation (6 kJ m(-2) d(-1)) had similar light-saturated photosynthetic rates but up to 50% lower stomatal conductance rates, as compared to plants grown without UV-B radiation. Growth responses of Arabidopsis to UV-B radiation included lower leaf area (25%) and biomass (10%) and higher UV-B absorbing compounds (30%) and chlorophyll content (52%). Lower stomatal conductance rates for plants grown with UV-B radiation were, in part, due to lower stomatal density on the adaxial surface. Plants grown with UV-B radiation had more capacity to down regulate photochemical efficiency of photosystem II (PSII) as shown by up to 25% lower phi(PSII) and 30% higher non-photochemical quenching of chlorophyll fluorescence under saturating light. These contributed to a smaller reduction in the maximum photochemical efficiency of PSII (F (v)/F (m)), greater dark-recovery of F (v)/F (m), and higher light-saturated carbon assimilation and stomatal conductance and transpiration rates after a four-hour high light treatment for plants grown with UV-B radiation. Plants grown with UV-B were more tolerant to a 12 day drought treatment than plants grown without UV-B as indicated by two times higher photosynthetic rates and 12% higher relative water content. UV-B-grown plants also had three times higher proline content. Higher tolerance to drought stress for Arabidopsis plants grown under UV-B radiation may be attributed to both increased proline content and decreased stomatal conductance. Growth of Arabidopsis in a UV-B-enhanced light regime increased tolerance to high light exposure and drought stress.
ResumoAs espécies de Piper são de grande interesse medicinal. Porém apresentam considerável desafio taxonômico, provavelmente pelo diminuto tamanho das partes florais. Por isso a morfologia externa da folha tem sido muito utilizada para taxonomia do grupo. Entretanto, há poucos trabalhos anatômicos para o gênero. Neste estudo, as folhas de nove espécies foram comparadas anatomicamente: Piper aduncum Vell.; P. cernuum Vell.; P. dilatatum Rich; P. gaudichaudianum Kunth; P. glabratum Kunth; P. hispidinervum C. DC.; P. lindbergii C. DC.; P. solmsianum C. DC. e P. umbellatum Jacq. O objetivo era avaliar o potencial dos caracteres anatômicos para separação de espécies. A maioria das espécies estudadas tem a epiderme do limbo constituída por células retangulares e arredondadas. Camadas subepidérmicas ocorrem em ambas às faces do limbo, exceto em P. aduncum, P. cernuum e P. hispidinervum. Todas as espécies são hipoestomáticas, exceto P. hispidinervum. O mesofilo é dorsiventral na maioria das espécies, enquanto em P. solmsianum e P. umbellatum o mesofilo é homogêneo. O número de camadas dos tecidos paliçádico e esponjoso é variável. Também ocorrem variações no número e no tamanho dos feixes vasculares. Em geral, ocorrem células secretoras, idioblastos, tricomas tectores e glandulares, lipídios, compostos fenólicos e amido. A análise de agrupamento identificou três grupos distintos entre as espécies, com base nas características anatômicas estudadas. Palavras-chave: anatomia, folha, Piperaceae, Piper. AbstractThe species of Piper are of great medical interest. They, however, represent considerable taxonomic challenge, probably due to the small size of floral parts. Therefore, the external morphology of the leaf has been used as diagnostic features in the taxonomy of the group. However, there are few anatomical studies on species of this genus. In this study, the leaves of nine species were compared anatomically: Piper aduncum Vell., P. cernuum Vell., P. dilatatum Rich, P. gaudichaudianum Kunth, P. glabratum Kunth, P. hispidinervum C. DC., P. lindbergii C. DC., P. solmsianum C. DC. and P. umbellatum Jacq. The objective was to evaluate the potential of anatomical characters for species separation. Most species studied have the epidermis of the lamina consists of rectangular and rounded cells. Subepidermal layers occur on both sides of the lamina, except in P. aduncum, P. cernuum and P. hispidinervum. All species are hypostomatic, except P.hispidinervum. The mesophyll is dorsiventral in most species, while in P. solmsianum and P. umbellatum, the mesophyll is homogeneous. The number of layers of palisade and spongy tissue is variable. Also there are variations in the number and size of vascular bundles. In general, secreting cells, idioblasts, and glandular trichomes, lipids, phenolic compounds and starch are present. Cluster analysis identified three distinct groups of species based on anatomical features studied.
RESUMO -(Nutrientes foliares de espécies arbóreas de três estádios sucessionais de floresta ombrófila densa no sul do Brasil). As concentrações de macro e micronutrientes foliares de espécies arbóreas foram avaliadas em três estádios sucessionais (inicial, intermediário e avançado) de uma floresta ombrófila densa das terras baixas, no litoral do Estado do Paraná, crescendo sobre solo arenoso e oligotrófico. Dentre as espécies arbóreas mais importantes de cada estádio sucessional (quatro iniciais; oito intermediárias; 11 avançadas), coletou-se folhas maduras de cinco diferentes indivíduos de cada estádio sucessional para a análise química dos seguintes elementos: N, P, K, Ca, Mg, C, Zn, Fe, Cu e Mn. As espécies do estádio inicial possuem as menores concentrações médias foliares de N, P, K, Zn, Fe e a maior concentração de Mg e estas concentrações são estatisticamente diferentes (p <0,05), quando comparadas com os valores médios dos demais estádios. Nos estádios intermediário e avançado, as concentrações médias de N, Ca e Mg, assim como os micronutrientes estão dentro dos valores esperados para florestas tropicais. As concentrações médias de K, nos estádios inicial e intermediário, e as concentrações médias de P, em todos os estádios, encontram-se abaixo dos valores reportados para as florestas tropicais. A relação C/N é alta (>25:1), apesar da tendência de diminuir à medida que avança a sucessão. O aumento da concentração da maioria dos nutrientes foliares analisados ao longo do gradiente sucessional está associado, possivelmente, com o incremento do acúmulo da serapilheira sobre o solo, o que proporciona ciclagem de nutrientes mais intensa e maiores concentrações de nutrientes no solo. :1), despite of the tendency to decrease as succession advances. The increment of concentration of the most studied foliar nutrients along the successional gradient is probably related to the accumulation of litter above the soil that provides a more adequate environment for efficient nutrient cycling and higher nutrient concentration in the soil. Palavras
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