RESUMO
Sargassum cymosum was exposed to cadmium (Cd) to determine any physiological and ultrastructural effects. To accomplish this, S. cymosum samples were cultivated under photosynthetic active radiation (PAR) and Cd (0, 0.1, 0.2, 0.4 and 0.8 mg L-1) during 7 and 14 days in laboratory-controlled conditions (0 mg L-1 Cd at both exposure times as control). Seaweeds had high retention capacity (over 90 %) for both exposure times. Growth rates showed significant increases by 14 days, especially for 0.1 and 0.4 mg L-1 Cd. Photosynthetic parameters were unaffected by Cd treatments. Chlorophyll contents were present in higher concentrations for all Cd treatments compared to respective control. Carotenoid profile showed significant differences in total composition and proportion of fucoxanthin and ß-carotene, and no lutein was detected at 14 days. Phenolic and flavonoid compounds showed major accumulation at 14 days. Transmission electron microscopy (TEM) analyses presented major alterations in Cd-treated samples, when compared with respective control, in particular disorganization of cell wall fibrils. When compared to respective control samples, multivariate analyses showed disparate and complex interactions among metabolites in Cd-exposed seaweeds, giving evidence of physiological defence response. Thus, it can be concluded that Cd is a stressor for S. cymosum, resulting in physiological and structural alterations related to defence mechanisms against oxidative stress and toxicological effects resulting from long-term metal exposure. However, in the present paper, some observed changes also appear to result from acclimation mechanisms under lower concentration of Cd relative to the tolerance of S. cymosum to experimental conditions.
Assuntos
Cádmio/toxicidade , Sargassum/citologia , Sargassum/metabolismo , Alga Marinha/citologia , Alga Marinha/metabolismo , Análise de Variância , Antioxidantes/metabolismo , Cádmio/análise , Carboidratos/análise , Sobrevivência Celular/efeitos dos fármacos , Clorofila/metabolismo , Clorofila A , Cromatografia Líquida de Alta Pressão , Flavonoides/análise , Fluorescência , Análise Multivariada , Fenóis/análise , Fotossíntese/efeitos dos fármacos , Análise de Componente Principal , Sargassum/efeitos dos fármacos , Sargassum/ultraestrutura , Água do Mar/química , Alga Marinha/efeitos dos fármacos , Alga Marinha/ultraestrutura , SolubilidadeRESUMO
Species in the genus Gracilaria that display conspicuously flattened vegetative morphologies are a taxonomically challenging group of marine benthic red algae. This is a result of their species richness, morphological similarity, and broad phenotypic plasticity. Within this group, the Gracilaria domingensis complex is one of the most common, conspicuous, and morphologically variable species along the tropical western Atlantic Ocean. Previous research has identified that members of this complex belong to two distantly related clades. However, despite this increased phylogentic resolution, species delimitations within each of these clades remain unclear. Our study assessed the species diversity within this difficult complex using morphological and molecular data from three genetic markers (cox1, UPA, and rbcL). We additionally applied six single-marker species delimitation methods (SDM: ABGD, GMYCs, GMYCm, SPN, bPTP, and PTP) to rbcL, which were largely in agreement regarding species delimitation. These results, combined with our analysis of morphology, indicate that the G. domingensis complex includes seven distinct species, each of which are not all most closely related: G. cervicornis; a ressurected G. ferox; G. apiculata subsp. apiculata; a new species, Gracilaria baiana sp. nov.; G. intermedia subsp. intermedia; G. venezuelensis; and G. domingensis sensu stricto, which includes the later heterotypic synonym, G. yoneshigueana. Our study demonstrates the value of multipronged strategies, including the use of both molecular and morphological approaches, to decipher cryptic species of red algae.
Assuntos
Gracilaria/classificação , Alga Marinha/classificação , Proteínas de Algas/genética , Região do Caribe , DNA de Algas/genética , Gracilaria/citologia , Gracilaria/genética , América do Norte , Filogenia , RNA Ribossômico 23S/genética , Alga Marinha/citologia , Alga Marinha/genética , Análise de Sequência de DNA , América do Sul , Especificidade da EspécieRESUMO
The culture and physiology of red macroalgae calluses are well documented. To date, however, no report has either performed a cytochemical analysis or characterized the ultrastructural organization of calluses at different stages of development and under the effect of plant growth regulators. Therefore, to undertake such analyses, this work studied the red seaweed Gracilariopsis tenuifrons (Bird et Oliveira) Fredericq et Hommersand. Morphology studies suggested three types of calluses: a) terminal callus having an irregular amorphous shape and filamentous projections originating from the cortical region of the thallus; b) apical callus growing on apical branches and having an elongated semispherical shape; and c) intercalary callus developing along the intermediary region of the thallus and having the appearance of small declivities with irregular edges. The abundance of intercalary calluses over terminal and apical calluses is most likely a result of a major cortical surface that would support the cellular growth required to generate calluses. Callus development was initially observed as a matrix of cellular disorganization with filamentous projections; then, the cellular mass seemed to become more compact with spherical uncolored aspect. The presence of starch grains in the inner part of the explant could be explained by absorption from the culture medium and by proper biosynthesis during callus development. Cell wall reaction to staining suggested cellulose and agar composition with acidic polysaccharides. Results suggest that none of the three morphological types of calluses showed any significant differences on the basis of either cytochemistry or ultrastructural organization.
Assuntos
Alga Marinha/citologia , Alga Marinha/ultraestrutura , Histocitoquímica , MicroscopiaRESUMO
The effect of drying Sargassum filipendula on the kinetics and uptake of cadmium was studied. The maximum uptake was not reduced when ovendried biomass was used for cadmium concentrations from 10.0 to 500.0 mg/L. Kinetics indicated better performance of the in natura biomass. Drying at 333 K affected the uptake capacity. Results fit the Langmuir model better than the Freundlich. This process followed pseudo-second-order kinetics. Thermogravimetric and infrared analysis confirmed that no structural damage occurred after drying, and no differences between the biomasses were observed. Temperatures from 303 to 328 K affected cadmium uptake capacity.