RESUMO
Pfaffia glomerata possesses potential pharmacological and medicinal properties, mainly owing to the secondary metabolite 20-hydroxyecdysone (20E). Increasing production of biomass and 20E is important for industrial purposes. This study aimed to evaluate the influence of irradiance on plant morphology and production of 20E in P. glomerata grown in vitro. Nodal segments of accessions 22 and 43 (Ac22 and Ac43) were inoculated in culture medium containing MS salts and vitamins. Cultures were maintained at 25 ± 2 °C under a 16-h photoperiod and subjected to irradiance treatments of 65, 130, and 200 µmol m-2 s-1 by fluorescent lamps. After 30 days, growth parameters, pigment content, stomatal density, in vitro photosynthesis, metabolites content, and morphoanatomy were assessed. Notably, Ac22 plants exhibited 10-fold higher 20E production when cultivated at 200 µmol m-2 s-1 than at 65 µmol m-2 s-1, evidencing the importance of light quantity for the accumulation of this metabolite. 20E production was twice as high in Ac22 as in Ac43 plants although both accessions responded positively to higher irradiance. Growth under 200 µmol m-2 s-1 stimulated photosynthesis and consequent biomass accumulation, but lowered carotenoids and anthocyanins. Furthermore, increasing irradiance enhanced the number of palisade and spongy parenchyma cells, enhancing the overall growth of P. glomerata. Graphical abstract.
Assuntos
Amaranthaceae/química , Fotossíntese/genética , Técnicas In VitroRESUMO
BACKGROUND: The determination of kinetic parameters and the development of mathematical models are of great interest to predict the growth of microalgae, the consumption of substrate and the design of photobioreactors focused on CO2 capture. However, most of the models in the literature have been developed for CO2 concentrations below 10%. RESULTS: A nonaxenic microalgal consortium was isolated from landfill leachate in order to study its kinetic behavior using a dynamic model. The model considered the CO2 mass transfer from the gas phase to the liquid phase and the effect of light intensity, assimilated nitrogen concentration, ammonium concentration and nitrate concentration. The proposed mathematical model was adjusted with 13 kinetic parameters and validated with a good fit obtained between experimental and simulated data. CONCLUSIONS: Good results were obtained, demonstrating the robustness of the proposed model. The assumption in the model of DIC inhibition in the ammonium and nitrate uptakes was correct, so this aspect should be considered when evaluating the kinetics with microalgae with high inlet CO2 concentrations.
Assuntos
Dióxido de Carbono/análise , Microalgas/efeitos da radiação , Microalgas/fisiologia , Cinética , Vertedores , Fótons , Microalgas/isolamento & purificação , Microalgas/crescimento & desenvolvimento , Fotobiorreatores , Águas Residuárias , Modelos Biológicos , Nitratos , NitrogênioRESUMO
The inactivation of the chloroplast ascorbate peroxidases (chlAPXs) has been thought to limit the efficiency of the water-water cycle and photo-oxidative protection under stress conditions. In this study, we have generated double knockdown rice (Oryza sativa L.) plants in both OsAPX7 (sAPX) and OsAPX8 (tAPX) genes, which encode chloroplastic APXs (chlAPXs). By employing an integrated approach involving gene expression, proteomics, biochemical and physiological analyses of photosynthesis, we have assessed the role of chlAPXs in the regulation of the protection of the photosystem II (PSII) activity and CO2 assimilation in rice plants exposed to high light (HL) and methyl violagen (MV). The chlAPX knockdown plants were affected more severely than the non-transformed (NT) plants in the activity and structure of PSII and CO2 assimilation in the presence of MV. Although MV induced significant increases in pigment content in the knockdown plants, the increases were apparently not sufficient for protection. Treatment with HL also caused generalized damage in PSII in both types of plants. The knockdown and NT plants exhibited differences in photosynthetic parameters related to efficiency of utilization of light and CO2. The knockdown plants overexpressed other antioxidant enzymes in response to the stresses and increased the GPX activity in the chloroplast-enriched fraction. Our data suggest that a partial deficiency of chlAPX expression modulate the PSII activity and integrity, reflecting the overall photosynthesis when rice plants are subjected to acute oxidative stress. However, under normal growth conditions, the knockdown plants exhibit normal phenotype, biochemical and physiological performance.
Assuntos
Ascorbato Peroxidases/genética , Proteínas de Cloroplastos/genética , Oryza/genética , Estresse Oxidativo/fisiologia , Fotossíntese/genética , Proteínas de Plantas/genética , Ascorbato Peroxidases/metabolismo , Proteínas de Cloroplastos/metabolismo , Eletroforese em Gel Bidimensional , Regulação Enzimológica da Expressão Gênica/efeitos dos fármacos , Regulação Enzimológica da Expressão Gênica/efeitos da radiação , Regulação da Expressão Gênica de Plantas/efeitos dos fármacos , Regulação da Expressão Gênica de Plantas/efeitos da radiação , Herbicidas/farmacologia , Isoenzimas/genética , Isoenzimas/metabolismo , Luz , Oryza/efeitos dos fármacos , Oryza/efeitos da radiação , Estresse Oxidativo/efeitos da radiação , Paraquat/farmacologia , Fotossíntese/efeitos dos fármacos , Fotossíntese/efeitos da radiação , Proteínas de Plantas/metabolismo , Plantas Geneticamente Modificadas , Interferência de RNA , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Espectrometria de Massas por Ionização por ElectrosprayRESUMO
The physiological responses of C4 species to simultaneous water deficit and low substrate temperature are poorly understood, as well as the recovery capacity. This study investigated whether the effect of these abiotic stressors is cultivar-dependent. The differential responses of drought-resistant (IACSP94-2094) and drought-sensitive (IACSP97-7065) sugarcane cultivars were characterized to assess the relationship between photosynthesis and antioxidant protection by APX and SOD isoforms under stress conditions. Our results show that drought alone or combined with low root temperature led to excessive energetic pressure at the PSII level. Heat dissipation was increased in both genotypes, but the high antioxidant capacity due to higher SOD and APX activities was genotype-dependent and it operated better in the drought-resistant genotype. High SOD and APX activities were associated with a rapid recovery of photosynthesis in IACSP94-2094 plants after drought and low substrate temperature alone or simultaneously.
Assuntos
Ascorbato Peroxidases/genética , Temperatura Baixa , Secas , Fotossíntese/genética , Saccharum/genética , Superóxido Dismutase/genética , Água , Adaptação Fisiológica/genética , Antioxidantes/metabolismo , Ascorbato Peroxidases/metabolismo , Genótipo , Fenótipo , Complexo de Proteína do Fotossistema II/metabolismo , Transpiração Vegetal , Saccharum/enzimologia , Saccharum/metabolismo , Estresse Fisiológico/genética , Superóxido Dismutase/metabolismoRESUMO
The aim of the present study was to evaluate the growth and development of apple rootstock shoots submitted to different photon flux densities (7, 14, 21 and 60 µmol m-2 s-1) and three culture media. The best photon flux for maximizing growth, number of shoots and leaves was 14 µmol m-2 s-1, which also resulted in the highest values of chloroplastic pigments. On the other hand, the highest photon flux (60 µmol m-2 s-1) decreased significantly these parameters. Medium with reduced sucrose concentration did not affect the analyzed parameters, enabling an efficient multiplication of the cultivar with only 1 percent of sucrose.
O objetivo do presente estudo foi avaliar características de crescimento e desenvolvimento de brotações de macieira submetidas a diferentes densidades de fluxo de fótons (7, 14, 21 e 60 µmol m-2 s-1) e três meios de cultura. O melhor fluxo de fótons para maximizar o crescimento, número de brotações e de folhas foi de 14 µmol m-2 s-1, o qual também proporcionou os maiores valores de pigmentos cloroplastídicos. Por outro lado, alto fluxo de fótons (60 µmol m-2 s-1) diminuiu significativamente os parâmetros citados acima. O meio com concentração reduzida de sacarose não afetou os parâmetros analisados, possibilitando uma multiplicação eficiente desta cultivar com apenas 1 por cento deste carboidrato.
RESUMO
Only recently have studies addressed the effect of early-colonizing vegetation on tree seedling survival and growth during secondary succession in tropical old fields, and few studies have elucidated the physiological responses of tree seedlings to different vegetational communities. We compared growth and various photosynthetic parameters for seedlings of four rain-forest tree species, Cedrela tonduzii, Inga punctata, Ocotea whitei, and Tapirira mexicana, growing in areas of pasture grass and shrubs in early-successional abandoned pasture in Costa Rica; in addition, we made measurements for two species in forest gaps. We tested the general hypothesis that early-colonizing shrubs facilitate growth of forest tree seedlings. Specifically, we measured microclimate, growth, CO2 assimilation, stomatal conductance, photosystem II quantum yield (ΦPSII), and xanthophyll pigment pools for all seedlings. Photosynthetic flux density (PFD) was higher under grass than shrubs or forest gaps, but was highly variable in each growth environment. For three of the four species, height growth was greatest in the grass compared to the shrubs and forest gaps; growth was similar below grass and shrubs for O. whitei. Photosynthetic capacity, apparent quantum yield, and stomatal conductance did not vary across habitats, but light compensation point and PFD at light saturation tended to be higher in the grass compared to forest and shrub growth environments. Water use efficiency differed across growth environments for three of the species. For plants in ambient PFD and dark-adapted plants, the efficiency of excitation energy transfer through PSII was lowest for plants in the grass compared to shrubs and forest gaps and also differed across species. Measurement of steady-state responses of ΦPSII to increasing PFD indicated a significant effect of growth environment at low PFD for all species and significant effects at high PFD only for I. punctata. All species exhibited a high degree of midday xanthophyll de-epoxidation in the different growth environments. Xanthophyll pigment pool size on an area basis was highest in the grass compared to shrubs and forest gaps for all four species. The results suggest that shrubs do not provide a facilitative effect for growth or photosynthesis for ~1.5-year-old seedlings of these four species. We conclude that site differences in success of tree seedlings during succession are a result of complex interactions of facilitation and competition and are not simply based on physiological responses to PFD.