RESUMEN
Browning and nutrient inputs from extreme rainfall, together with increased vertical mixing due to strong winds, are more frequent in coastal ecosystems; however, their interactive effects on phytoplankton are poorly understood. We conducted experiments to quantify how browning, together with different mixing speeds (fluctuating radiation), and a nutrient pulse alter primary productivity and photosynthetic efficiency in estuarine phytoplankton communities. Phytoplankton communities (grazers excluded) were exposed simultaneously to these drivers, and key photosynthetic targets were quantified: oxygen production, electron transport rates (ETRs), and carbon fixation immediately following collection and after a 2-d acclimation/adaptation period. Increasing mixing speeds in a turbid water column (e.g. browning) significantly decreased ETRs and carbon fixation in the short term. Acclimation/adaptation to this condition for 2 d resulted in an increase in nanoplanktonic diatoms and a community that was photosynthetically more efficient; however, this did not revert the decreasing trend in carbon fixation with increased mixing speed. The observed interactive effects (resulting from extreme rainfall and strong winds) may have profound implications in the trophodynamics of highly productive system such as the Southwest Atlantic Ocean due to changes in the size structure of the community and reduced productivity.
Asunto(s)
Diatomeas , Fitoplancton , Ecosistema , Viento , Fotosíntesis/efectos de la radiaciónRESUMEN
High irradiance and increased air temperature during extreme weather conditions affect tree crops and impact the yield and quality of fruits. Moreover, flowering and fruit set of Citrus are likely impaired by UV radiation and/or reduced carbon assimilation, which increase reactive oxygen species production and damage the leaf photosynthetic apparatus. Particle coating films sprayed on leaves have been offered as a way to minimize crop losses due to the climate change scenario, even though the extent of leaf protection is not characterized. We evaluated the use of two protective films on the oxidative stress and leaf photosynthesis of sweet orange trees exposed to varying daylight levels. Trees were maintained under full sun light, sprayed or not (control) with kaolin or calcium carbonate, and under reduced irradiance using either aluminum shade cloth 50% or anti-UV transparent plastic. Kaolin or calcium carbonate reflected 20%-30% of the incident light on the leaf surface compared to leaves not sprayed and under full sunlight. Leaves with coating exhibited improved CO2 assimilation and photosystem II efficiency, and lower leaf temperatures over time. In addition, the coating protected leaves against excess irradiance due to dissipation of excess energy into the photosynthetic apparatus (NPQt). Nonenzymatic mechanisms for UV protection, such as carotenoids, were higher in full sun control plants than in leaf-coated plants. Comparable responses were observed on trees maintained covered either by the cloth or the plastic film. Finally, we conclude that the use of suspension particles mitigates the harmful effects of excess UV irradiance and temperature in sweet orange trees.
Asunto(s)
Citrus , Árboles , Árboles/fisiología , Temperatura , Caolín/farmacología , Fotosíntesis/efectos de la radiación , Hojas de la Planta/fisiologíaRESUMEN
Ionizing radiation of astrophysical origin might have played an important role in biological evolution during the long course of Earth's evolution. Several phenomena might have induced intense fluctuations in background ionizing radiation, such as highly energetic stellar explosions. There might also be anthropogenic causes for environmental radiation fluctuations, resulting from nuclear industry activities. The inclusion of these effects in a mathematical model for photosynthesis provides a useful tool to account for the damages of the above-mentioned phenomena in vegetal life. Mathematical models for photosynthesis typically only consider ultraviolet radiation and photosynthetically active radiation, as they have been a ubiquitous physical factor in the settlement of vegetal life. In this work a mathematical model for aquatic photosynthesis is modified, from first principles, to include the action of particulate ionizing radiation on the photosynthetic process. After assuming an ansatz allowing to separate damage/repair kinetics of ultraviolet and ionizing radiations, a treatable mathematical expression of the model is obtained. This generalized model is presented as a function of radiometric and photometric magnitudes, making it prone to calibration and useful to apply to aquatic ecosystems under radiational stress due to gamma-ray bursts, cosmic ray bursts, solar storms, or other sources of ionizing radiations.
Asunto(s)
Modelos Teóricos , Fotosíntesis/efectos de la radiación , Radiación Ionizante , Fitoplancton/fisiología , Fitoplancton/efectos de la radiaciónRESUMEN
Competition for light between neighboring plants has important consequences for plant fitness and crop productivity. Studies on the molecular mechanisms of plant responses to neighbor proximity have been largely based on the model species Arabidopsis thaliana grown under controlled light environments. These controlled conditions commonly use fluorescent tubes for the main light source for photosynthesis and filtered light form incandescent bulbs to adjust the ratio of red (R) to far-red (FR) radiation. However, both of these types of bulbs are being discontinued and replaced by more efficient sources based on light emitting diodes (LEDs). For that reason, there is a need to evaluate alternative light sources, which can phenocopy the physiological and molecular results obtained with traditional lighting systems. Here we evaluate a custom-made LED culture module that can be used to effectively evaluate shade-avoidance responses, yielding results that, in Arabidopsis, are comparable to those obtained using traditional lighting systems.
Asunto(s)
Proteínas de Arabidopsis/genética , Arabidopsis/crecimiento & desarrollo , Perfilación de la Expresión Génica/métodos , Arabidopsis/genética , Arabidopsis/efectos de la radiación , Regulación de la Expresión Génica de las Plantas/efectos de la radiación , Luz/efectos adversos , Fenotipo , Fotosíntesis/efectos de la radiaciónRESUMEN
Our search for candidates for photosynthesis inhibitors is allowing us to report the effect of two acetogenins identified in Annona coriacea Mart. leaves, ACG-A and ACG-B, a non-adjacent bis-THF and a mono-THF types, respectively. This is an important class of natural products which presents biological properties such as anticancer, neurotoxic, larvicidal and insecticidal. However, this is only the second report associated to its herbicidal activity. Their mechanisms of action on the light reactions of the photosynthesis were elucidated by polarographic techniques. Compounds inhibited the noncyclic electron transport on basal, phosphorylating, and uncoupled conditions from H2 O to methyl viologen (MV); therefore, they act as Hill reaction inhibitors. Studies on fluorescence of chlorophyll a (ChL a) indicated that they inhibited the acceptor side of PSII between P680 and PQ-pool, exactly as the commercial herbicide DCMU does.
Asunto(s)
Acetogeninas/química , Annona/química , Acetogeninas/aislamiento & purificación , Acetogeninas/metabolismo , Acetogeninas/farmacología , Annona/metabolismo , Clorofila A/química , Cloroplastos/metabolismo , Transporte de Electrón/efectos de los fármacos , Luz , Fotosíntesis/efectos de los fármacos , Fotosíntesis/efectos de la radiación , Complejo de Proteína del Fotosistema II/antagonistas & inhibidores , Complejo de Proteína del Fotosistema II/metabolismo , Hojas de la Planta/química , Hojas de la Planta/metabolismo , Spinacia oleracea/metabolismoRESUMEN
The presence, biosynthesis and functional role of sterols in the green microalga Haematococcus pluvialis remain poorly understood. In this work we studied the effect of high-light (HL) stress on sterol synthesis in H. pluvialis UTEX 2505 cells. HL stress induced the synthesis of sterols in parallel with that of triacylglycerides (TAG), giving rise to the synthesis of cholesterol over that of phytosterols. Blockage of the carotenogenic 1-deoxy-D-xylulose 5-phosphate (MEP) pathway is shown to be involved in HL-induced sterol synthesis. In addition, high irradiance exposure induced MEP- and fatty acid (FA)-biosynthetic transcripts. The pharmacological inhibition of these pathways suggests a possible feedback regulation of sterol and FA homeostasis. Finally, both lipid classes proved crucial to the adequate photosynthetic performance of H. pluvialis grown under HL intensity stress. Our findings reveal new insights into H. pluvialis lipid metabolism that contribute to the development of value-added bioproducts from microalgae.
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Metabolismo de los Lípidos/efectos de la radiación , Lípidos/genética , Fotosíntesis/genética , Esteroles/metabolismo , Ácidos Grasos/genética , Ácidos Grasos/metabolismo , Luz , Metabolismo de los Lípidos/genética , Microalgas/genética , Microalgas/metabolismo , Microalgas/efectos de la radiación , Fotosíntesis/efectos de la radiación , Estrés Fisiológico/genética , Estrés Fisiológico/efectos de la radiación , Xantófilas/metabolismo , Xantófilas/efectos de la radiaciónRESUMEN
Flavodoxins are electron carrier flavoproteins present in bacteria and photosynthetic microorganisms which duplicate the functional properties of iron-sulphur containing ferredoxins and replace them under adverse environmental situations that lead to ferredoxin decline. When expressed in plant chloroplasts, flavodoxin complemented ferredoxin deficiency and improved tolerance to multiple sources of biotic, abiotic and xenobiotic stress. Analysis of flavodoxin-expressing plants grown under normal conditions, in which the two carriers are present, revealed phenotypic effects unrelated to ferredoxin replacement. Flavodoxin thus provided a tool to alter the chloroplast redox poise in a customized way and to investigate its consequences on plant physiology and development. We describe herein the effects exerted by the flavoprotein on the function of the photosynthetic machinery. Pigment analysis revealed significant increases in chlorophyll a, carotenoids and chlorophyll a/b ratio in flavodoxin-expressing tobacco lines. Results suggest smaller antenna size in these plants, supported by lower relative contents of light-harvesting complex proteins. Chlorophyll a fluorescence and P700 spectroscopy measurements indicated that transgenic plants displayed higher quantum yields for both photosystems, a more oxidized plastoquinone pool under steady-state conditions and faster plastoquinone dark oxidation after a pulse of saturating light. Many of these effects resemble the phenotypes exhibited by leaves adapted to high irradiation, a most common environmental hardship faced by plants growing in the field. The results suggest that flavodoxin-expressing plants would be better prepared to cope with this adverse situation, and concur with earlier observations reporting that hundreds of stress-responsive genes were induced in the absence of stress in these lines.
Asunto(s)
Aclimatación/efectos de la radiación , Flavodoxina/genética , Regulación de la Expresión Génica de las Plantas/efectos de la radiación , Luz , Nicotiana/metabolismo , Fotosíntesis/efectos de la radiación , Hojas de la Planta/genética , Relación Dosis-Respuesta en la Radiación , Fenotipo , Hojas de la Planta/efectos de la radiación , Nicotiana/genética , Nicotiana/fisiología , Nicotiana/efectos de la radiaciónRESUMEN
Lippia rotundifolia Cham. is in the family Verbenaceae and is endemic to the Cerrado. This species is aromatic and characterized by the presence of glandular trichomes on its leaves that are rich in monoterpenes. The objective of this study was to evaluate the growth, photosynthetic pigment production, and chemical composition of L. rotundifolia grown in vitro under different light wavelengths and intensities. The light intensities consisted of five treatments using cool white fluorescent lamps at 20, 54, 78, 88, and 110⯵molâ¯m-2â¯s-1. The light quality consisted of six treatments using light-emitting diodes (LEDs) in different light wavelengths, namely, white, red, blue, and their interactions: 1R:1B, 2.5R:1B, and 1R:2.5B. After 45â¯days, the biometric parameters, photosynthetic pigment content, and volatile compounds were evaluated. The lower light intensities of 20 and 54⯵molâ¯m-2â¯s-1 generated higher growth, photosynthetic pigment content, and biomass accumulation. Myrcene and pentadecane were highest under light intensities of 88 and 110⯵molâ¯m-2â¯s-1, respectively. The highest limonene and ocimenone levels were obtained at 20 and 54⯵molâ¯m-2â¯s-1 intensity, respectively, and the highest myrcenone content was obtained at 78⯵molâ¯m-2â¯s-1 intensity. Regarding the light wavelengths, the combination of red and blue spectra further stimulated plantlet growth, and the 2.5R:1B combination obtained the best biometric data and total chlorophyll content. The z-ocimenone chemical compound contents were highest under the 1R:2.5B light spectrum. The monochromatic blue spectrum increased the myrcene and limonene content but decreased the myrcenone content, which was increased by red light. The highest pentadecane contents were obtained with the white spectrum and the red and blue combinations.
Asunto(s)
Luz , Lippia/metabolismo , Fotosíntesis/efectos de la radiación , Compuestos Orgánicos Volátiles/metabolismo , Clorofila/metabolismo , Cromatografía de Gases y Espectrometría de Masas , Limoneno/metabolismo , Lippia/química , Lippia/crecimiento & desarrollo , Hojas de la Planta/química , Hojas de la Planta/metabolismo , Análisis de Componente Principal , Compuestos Orgánicos Volátiles/análisisRESUMEN
Stomatal responses to environmental signals differ substantially between ferns and angiosperms. However, the mechanisms that lead to such different responses remain unclear. Here we investigated the extent to which leaf metabolism contributes to coordinate the differential stomatal behaviour among ferns and angiosperms. Stomata from all species were responsive to light and CO2 transitions. However, fern stomatal responses were slower and minor in both absolute and relative terms. Angiosperms have higher stomatal density, but this is not correlated with speed of stomatal closure. The metabolic responses throughout the diel course and under different CO2 conditions differ substantially among ferns and angiosperms. Higher sucrose content and an increased sucrose-to-malate ratio during high CO2 -induced stomatal closure was observed in angiosperms compared to ferns. Furthermore, the speed of stomatal closure was positively and negatively correlated with sugars and organic acids, respectively, suggesting that the balance between sugars and organic acids aids in explaining the faster stomatal responses of angiosperms. Our results suggest that mesophyll-derived metabolic signals, especially those associated with sucrose and malate, may also be important to modulate the differential stomatal behaviour between ferns and angiosperms, providing important new information that helps in understanding the metabolism-mediated mechanisms regulating stomatal movements across land plant evolution.
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Dióxido de Carbono/metabolismo , Helechos/fisiología , Luz , Magnoliopsida/fisiología , Malatos/metabolismo , Estomas de Plantas/metabolismo , Estomas de Plantas/efectos de la radiación , Sacarosa/metabolismo , Análisis Discriminante , Helechos/efectos de la radiación , Análisis de los Mínimos Cuadrados , Magnoliopsida/efectos de la radiación , Metaboloma/efectos de la radiación , Fotosíntesis/efectos de la radiación , Análisis de Componente PrincipalRESUMEN
Mechanisms involving ammonium toxicity, excess light, and photosynthesis are scarcely known in plants. We tested the hypothesis that high NH4+ supply in presence of high light decreases photosynthetic efficiency of rice plants, an allegedly tolerant species. Mature rice plants were previously supplied with 10 mM NH4+ or 10 mM NO3- and subsequently exposed to 400 µmol m-2 s-1 (moderate light-ML) or 2000 µmol m-2 s-1 (high light-HL) for 8 h. HL greatly stimulated NH4+ accumulation in roots and in a minor extent in leaves. These plants displayed significant delay in D1 protein recovery in the dark, compared to nitrate-supplied plants. These responses were related to reduction of both PSII and PSI quantum efficiencies and induction of non-photochemical quenching. These changes were also associated with higher limitation in the donor side and lower restriction in the acceptor side of PSI. This later response was closely related to prominent decrease in stomatal conductance and net CO2 assimilation that could have strongly affected the energy balance in chloroplast, favoring ATP accumulation and NPQ induction. In parallel, NH4+ induced a strong increase in the electron flux to photorespiration and, inversely, it decreased the flux to Rubisco carboxylation. Overall, ammonium supply negatively interacts with excess light, possibly by enhancing ammonium transport towards leaves, causing negative effects on some photosynthetic steps. We propose that high ammonium supply to rice combined with excess light is capable to induce strong delay in D1 protein turnover and restriction in stomatal conductance, which might have contributed to generalized disturbances on photosynthetic efficiency.
Asunto(s)
Compuestos de Amonio/toxicidad , Oryza/fisiología , Cloroplastos/metabolismo , Metabolismo Energético , Luz , Oryza/efectos de la radiación , Fotosíntesis/efectos de los fármacos , Fotosíntesis/efectos de la radiación , Complejo de Proteína del Fotosistema I/metabolismo , Complejo de Proteína del Fotosistema II/metabolismo , Hojas de la Planta/fisiología , Hojas de la Planta/efectos de la radiación , Raíces de Plantas/fisiología , Raíces de Plantas/efectos de la radiación , Ribulosa-Bifosfato Carboxilasa/metabolismoRESUMEN
Regional climate change in Antarctica would favor the carbon assimilation of Antarctic vascular plants, since rising temperatures are approaching their photosynthetic optimum (10-19°C). This could be detrimental for photoprotection mechanisms, mainly those associated with thermal dissipation, making plants more susceptible to eventual drought predicted by climate change models. With the purpose to study the effect of temperature and water availability on light energy utilization and putative adjustments in photoprotective mechanisms of Deschampsia antarctica Desv., plants were collected from two Antarctic provenances: King George Island and Lagotellerie Island. Plants were cultivated at 5, 10 and 16°C under well-watered (WW) and water-deficit (WD, at 35% of the field capacity) conditions. Chlorophyll fluorescence, pigment content and de-epoxidation state were evaluated. Regardless of provenances, D. antarctica showed similar morphological, biochemical and functional responses to growth temperature. Higher temperature triggered an increase in photochemical activity (i.e. electron transport rate and photochemical quenching), and a decrease in thermal dissipation capacity (i.e. lower xanthophyll pool, Chl a/b and ß carotene/neoxanthin ratios). Leaf mass per unit area was reduced at higher temperature, and was only affected in plants exposed to WD at 16°C and exhibiting lower electron transport rate and amount of chlorophylls. D. antarctica is adapted to frequent freezing events, which may induce a form of physiological water stress. Photoprotective responses observed under WD contribute to maintain a stable photochemical activity. Thus, it is possible that short-term temperature increases could favor the photochemical activity of this species. However, long-term effects will depend on the magnitude of changes and the plant's ability to adjust to new growth temperature.
Asunto(s)
Luz , Poaceae/metabolismo , Agua/metabolismo , Fotosíntesis/efectos de la radiación , Poaceae/efectos de la radiación , TemperaturaRESUMEN
Previous studies of heat tolerance of tropical trees have focused on canopy leaves exposed to full sunlight and high temperatures. However, in lowland tropical forests with leaf area indices of 5-6, the vast majority of leaves experience varying degrees of shade and a reduced heat load compared to sun leaves. Here we tested whether heat tolerance is lower in shade than in sun leaves. For three tropical tree species, Calophyllum inophyllum, Inga spectabilis, and Ormosia macrocalyx, disks of fully developed shade and sun leaves were subjected to 15-min heat treatments, followed by measurement of chlorophyll a fluorescence after 48 h of recovery. In two of the three species, the temperature causing a 50% decrease of the fluorescence ratio Fv/Fm (T50) was significantly lower (by ~ 1.0 °C) in shade than in sun leaves, indicating a moderately decreased heat tolerance of shade leaves. In shade leaves of these two species, the rise in initial fluorescence, F0, also occurred at lower temperatures. In the third species, there was no shade-sun difference in T50. In situ measurements of photosynthetic CO2 assimilation showed that the optimum temperature for photosynthesis tended to be lower in shade leaves, although differences were not significant. At supra-optimal temperatures, photosynthesis was largely constrained by stomatal conductance, and the high-temperature CO2 compensation point, TMax, occurred at considerably lower temperatures than T50. Our study demonstrates that the temperature response of shade leaves of tropical trees differs only marginally from that of sun leaves, both in terms of heat tolerance and photosynthetic performance.
Asunto(s)
Adaptación Fisiológica , Calor , Fotosíntesis , Hojas de la Planta/fisiología , Luz Solar , Árboles/fisiología , Clima Tropical , Adaptación Fisiológica/efectos de la radiación , Dióxido de Carbono/metabolismo , Clorofila A/metabolismo , Fluorescencia , Fotosíntesis/efectos de la radiación , Hojas de la Planta/efectos de la radiación , Estomas de Plantas/fisiología , Estomas de Plantas/efectos de la radiaciónRESUMEN
One of the main limitations of rice yield in regions of high productive performance is the light-use efficiency (LUE). LUE can be determined at the whole-plant level or at the photosynthetic apparatus level (quantum yield). Both vary according to the intensity and spectral quality of light. The aim of this study was to analyze the cultivar dependence regarding LUE at the plant level and quantum yield using four rice cultivars and four light environments. To achieve this, two in-house Light Systems were developed: Light System I which generates white light environments (spectral quality of 400-700 nm band) and Light System II which generates a blue-red light environment (spectral quality of 400-500 nm and 600-700 nm bands). Light environment conditioned the LUE and quantum yield in PSII of all evaluated cultivars. In white environments, LUE decreased when light intensity duplicated, while in blue-red environments no differences on LUE were observed. Energy partition in PSII was determined by the quantum yield of three de-excitation processes using chlorophyll fluorescence parameters. For this purpose, a quenching analysis followed by a relaxation analysis was performed. The damage of PSII was only increased by low levels of energy in white environments, leading to a decrease in photochemical processes due to the closure of the reaction centers. In conclusion, all rice cultivars evaluated in this study were sensible to low levels of radiation, but the response was cultivar dependent. There was not a clear genotypic relation between LUE and quantum yield.
Asunto(s)
Metabolismo Energético , Oryza/fisiología , Fotosíntesis/efectos de la radiación , Luz , Oryza/efectos de la radiación , Procesos Fotoquímicos , Fotones , Especificidad de la EspecieRESUMEN
The photosynthetic adjustments of macaw palm (Acrocomia aculeata) were evaluated in 30-day-old seedlings exposed to high and low light environments, and sudden transference from low to high light and comparisons were made with the hardening protocol used in nurseries. Furthermore, we evaluated the responses to long-term exposure (265 days) to high and low light environments. Macaw palm seedlings exhibited an efficient mechanism that maximized light capture under scarce conditions, and dissipated excess energy to avoid damaging to the photosystem II under high light. The seedlings showed low saturation irradiance but no photoinhibition when exposed to excess light. When grown under low light intensities, seedlings presented higher photochemical efficiency and minimized the respiratory costs with positive carbon balance at lower irradiance than hardened seedlings did. The hardening procedure did not appear to be an advantageous method during seedling production. Long-term exposure to either low or high light did not cause significant leaf anatomical adjustments. However, the low light seedlings showed higher leaf area and chlorophyll content than those exposed to higher light intensity did, which enabled shaded seedlings to maximize the captured light. Furthermore, the high non-photochemical dissipation allowed rapid acclimation to excessive light exposure. These responses allow macaw palm cultivation and establishment in very different light environments.
Asunto(s)
Aclimatación/fisiología , Arecaceae/efectos de la radiación , Luz , Hojas de la Planta/efectos de la radiación , Plantones/efectos de la radiación , Arecaceae/crecimiento & desarrollo , Arecaceae/metabolismo , Clorofila/metabolismo , Fotosíntesis/efectos de la radiación , Complejo de Proteína del Fotosistema II/metabolismo , Hojas de la Planta/crecimiento & desarrollo , Hojas de la Planta/metabolismo , Plantones/crecimiento & desarrollo , Plantones/metabolismo , Factores de TiempoRESUMEN
The jelly palm plant [Butia capitata (Martius) Beccari] is a native palm of the Cerrado biome used for many purposes in northern Minas Gerais State, Brazil. Dormancy is common in palm seeds, resulting in slow and uneven germination that may take years to complete. Modification in the growth pattern, anatomical parameters, physiological and biochemical characteristics of the plant can be verified due to changes in the light spectrum transmitted through colored shade nets used. Therefore, the objective of this study is to evaluate the effect of colored shade nets on the leaf and root anatomy of the jelly palm plant. The experiment was performed in a completely randomized design, with five treatments, ten replicates and eight plants per replicate, totaling 400 plants. Four colored photo-converter nets with 50% shading and different radiation proportions were employed: white (985 µmol.m-2.s-1), red (327 µmol.m-2.s-1), black (433 µmol.m-2.s-1) and silver (405 µmol.m-2.s-1). The plants cultivated under direct sunlight (1000 µmol.m-2.s-1) were considered as the control group. Leaf and root anatomical analysis was performed on 10 plants per treatment. It is possible to conclude that the colored shade nets caused changes in leaf and root anatomy of the jelly palm plant (Butia capitata).
Asunto(s)
Arecaceae/anatomía & histología , Color , Hojas de la Planta/crecimiento & desarrollo , Luz Solar , Arecaceae/clasificación , Arecaceae/crecimiento & desarrollo , Arecaceae/efectos de la radiación , Brasil , Fotosíntesis/efectos de la radiación , Hojas de la Planta/anatomía & histología , Hojas de la Planta/efectos de la radiaciónRESUMEN
Plastidial isoprenoids, such as carotenoids and tocopherols, are important anti-oxidant metabolites synthesized in plastids from precursors generated by the methylerythritol 4-phosphate (MEP) pathway. In this study, we found that irradiation of Arabidopsis thaliana plants with UV-B caused a strong increase in the accumulation of the photoprotective xanthophyll zeaxanthin but also resulted in slightly higher levels of γ-tocopherol. Plants deficient in the MEP enzymes 1-deoxy-D-xylulose 5-phosphate synthase and 1-hydroxy-2-methyl-2-butenyl 4-diphosphate synthase showed a general reduction in both carotenoids and tocopherols and this was associated with increased DNA damage and decreased photosynthesis after exposure to UV-B. Genetic blockage of tocopherol biosynthesis did not affect DNA damage accumulation. In contrast, lut2 mutants that accumulate ß,ß-xanthophylls showed decreased DNA damage when irradiated with UV-B. Analysis of aba2 mutants showed that UV-B protection was not mediated by ABA (a hormone derived from ß,ß-xanthophylls). Plants accumulating ß,ß-xanthophylls also showed decreased oxidative damage and increased expression of DNA-repair enzymes, suggesting that this may be a mechanism for these plants to decrease DNA damage. In addition, in vitro experiments also provided evidence that ß,ß-xanthophylls can directly protect against DNA damage by absorbing radiation. Together, our results suggest that xanthophyll-cycle carotenoids that protect against excess illumination may also contribute to protection against UV-B.
Asunto(s)
Arabidopsis/metabolismo , Rayos Ultravioleta , Xantófilas/metabolismo , Arabidopsis/enzimología , Arabidopsis/genética , Arabidopsis/efectos de la radiación , Eritritol/análogos & derivados , Eritritol/deficiencia , Fotosíntesis/efectos de la radiación , Fosfatos de Azúcar/deficienciaRESUMEN
Gevuina avellana (Proteaceae) is a typical tree from the South American temperate rainforest. Although this species mostly regenerates in shaded understories, it exhibits an exceptional ecological breadth, being able to live under a wide range of light conditions. Here we studied the genetic basis that underlies physiological acclimation of the photosynthetic responses of G. avellana under contrasting light conditions. We analyzed carbon assimilation and light energy used for photochemical processes in plants acclimated to contrasting light conditions. Also, we used a transcriptional profile of leaf primordia from G. avellana saplings growing under different light environments in their natural habitat, to identify the gene coexpression network underpinning photosynthetic performance and light-related processes. The photosynthetic parameters revealed optimal performance regardless of light conditions. Strikingly, the mechanism involved in dissipation of excess light energy showed no significant differences between high- and low-light-acclimated plants. The gene coexpression network defined a community structure consistent with the photochemical responses, including genes involved mainly in assembly and functioning of photosystems, photoprotection, and retrograde signaling. This ecophysiological genomics approach improves our understanding of the intraspecific variability that allows G. avellana to have optimal photochemical and photoprotective mechanisms in the diverse light habitats it encounters in nature.
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Regulación de la Expresión Génica de las Plantas/efectos de la radiación , Redes Reguladoras de Genes , Luz , Aclimatación/fisiología , Aclimatación/efectos de la radiación , Clorofila/metabolismo , Fluorescencia , Redes Reguladoras de Genes/efectos de la radiación , Fotosíntesis/efectos de la radiación , Hojas de la Planta/fisiología , Hojas de la Planta/efectos de la radiación , Transpiración de Plantas/efectos de la radiación , Análisis de Componente PrincipalRESUMEN
The purpose of this investigation was to determine the influence of colored shade nets on the growth, anatomy and essential oil content, yield and chemical composition of Pogostemon cablin. The plants were cultivated under full sunlight, black, blue and red nets. The harvesting was performed 5 months after planting and it was followed by the analysis of plant growth parameters, leaf anatomy, essential oil content, yield and chemical composition. The plants grown under red net have produced more leaf, shoot, total dry weight and leaf area. Plants cultivated under colored nets showed differences in morphological features. Plants maintained under red net had a higher leaf blade thickness and polar and equatorial diameter of the stomata ratio. Additionally, higher yield of essential oil in the leaves was observed under red and blue colored shade net. The essential oil of the plants grown under red net showed the highest relative percentage of patchoulol (66.84%). Therefore, it is possible using colored shade nets to manipulate P. cablin growth, as well as its essential oil production with several chemical compositions. The analyses of principal components allowed observing that pogostol has negative correlation with α-guaiene and α-bulnesene. There was difference in total dry weight and patchoulol content when the patchouli is cultured under the red colored shade nets.
Asunto(s)
Color , Luz , Aceites Volátiles/química , Hojas de la Planta/crecimiento & desarrollo , Pogostemon/crecimiento & desarrollo , Peso Corporal/efectos de la radiación , Producción de Cultivos/métodos , Oscuridad , Aceites Volátiles/efectos de la radiación , Fotosíntesis/efectos de la radiación , Hojas de la Planta/anatomía & histología , Hojas de la Planta/química , Hojas de la Planta/efectos de la radiación , Estomas de Plantas/química , Pogostemon/anatomía & histología , Pogostemon/efectos de la radiación , Tricomas/químicaRESUMEN
B-box (BBX) proteins are zinc-finger transcription factors containing one or two B-box motifs. BBX proteins act as key factors in the networks regulating growth and development. The relevance of BBX21 to light and abscisic acid signaling in seedling development is well established; however, its importance in adult plant development and agronomic species is poorly understood. Therefore, we studied the effect of heterologous expression of Arabidopsis (Arabidopsis thaliana) BBX21 in potato (Solanum tuberosum) var Spunta. Three independent AtBBX21-expressing lines and the wild-type control were cultivated under sunlight and at controlled temperatures in a greenhouse. By anatomical, physiological, biochemical, and gene expression analysis, we demonstrated that AtBBX21-expressing plants were more robust and produced more tubers than wild-type plants. Interestingly, AtBBX21-expressing plants had higher rates of photosynthesis, with a significant increase in photosynthetic gene expression, and higher stomatal conductance, with increased size of the stomatal opening, without any associated decline in water use efficiency. Furthermore, AtBBX21-expressing potato plants had reduced photoinhibition associated with higher production of anthocyanins and phenolic compounds, and higher expression of genes in the phenylpropanoid biosynthesis pathway. To gain insights into the mechanism of BBX21, we evaluated the molecular, morphological, metabolic, and photosynthetic behavior in adult BBX21-overexpressing Arabidopsis. We conclude that BBX21 overexpression improved morphological and physiological attributes, and photosynthetic rates in nonoptimal, high-irradiance conditions, without associated impairment of water use efficiency. These characteristics of BBX21 may be useful for increasing production of potatoes, and potentially of other crops.
Asunto(s)
Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , Luz , Fotosíntesis/efectos de la radiación , Solanum tuberosum/fisiología , Solanum tuberosum/efectos de la radiación , Factores de Transcripción/metabolismo , Antocianinas/metabolismo , Regulación de la Expresión Génica de las Plantas/efectos de la radiación , Fenoles/metabolismo , Estomas de Plantas/fisiología , Estomas de Plantas/efectos de la radiación , Tubérculos de la Planta/crecimiento & desarrollo , Plantas Modificadas Genéticamente , Propanoles/metabolismo , Transducción de Señal , Solanum tuberosum/genéticaRESUMEN
Mixotrophy is a metabolic strategy in which an organism is autotrophic and heterotrophic simultaneously. Considering that the aquatic environment provides several organic sources of carbon, it is probably common for microalgae to perform mixotrophy and not only photoautotrophy, but little is known about microalgae mixotrophy. The present work aimed at investigating the growth, photosynthetic activity, morphology, and biochemical composition of the microalga Chlorella sorokiniana in mixotrophic and photo-mixotrophic conditions, comparing it with photoautotrophy. The results showed pH changes after glucose addition, reaching pH 11.62 in mixotrophic and 10.47 in sequential photo-mixotrophic cultures, which limited the microalgal growth. Highest biomass was obtained in the mixotrophic culture in comparison with the sequential photo-mixotrophic one. Rapid light saturation curves showed that α (photosynthetic efficiency, 1.69) and relative electron transport rate (rETR; 565.61) were higher in the mixotrophic cultures, whereas the highest Ik (irradiance saturation, 386.68) was obtained in the photoautotrophic ones. In the sequential photo-mixotrophic cultures, photosynthetic activity varied during glucose consumption, decreasing the maximum quantum yield Fv/Fm after glucose addition, indicating change in metabolism, from photoautotrophy to mixotrophy by the microalga. The results showed that the mixotrophic cultures had higher production of chlorophyll a (6.26 mg mL-1), cell density (6.62 × 107 cell mL-1), and lipids (0.06 pg µm-3). Sequential photo-mixotrophic cultures showed the highest biovolume (360.5 µm3 cell-1) and total carbohydrates (0.026 pg µm-3). The protein concentration was 3.2 and 2.4 times higher in photoautotrophy and photo-mixotrophic growth, respectively, than in mixotrophy, but lipids were three times higher under mixotrophy. The biochemical changes we observed indicate that the microalga's plasticity in face of new environmental characteristics, such as the presence of organic carbon, can change the flow of energy through natural ecosystems.