RESUMO
Sheep and goat production takes place under unsuitable climate conditions, where animals are more susceptible to high temperatures. The objectives of this study were to determine, i) whether sexual behavior of photo-stimulated bucks varies through 24 h/day in March and April and, ii) whether the environmental temperature and the relative humidity affect their expression. Six bucks were submitted to artificial long days (16 h light and 8 h darkness per day/2.5 months). Bucks were exposed to ovariectomized females once a week during the non-breeding period and sexual behavior was recorded for 15 min at 2 h intervals along 24 h/day. The environmental temperature, relative humidity, temperature-humidity index (THI), and body temperature were recorded in each behavior test. Plasma testosterone, sexual behavior, environmental temperature, relative humidity, and body temperature were analyzed using Generalized Estimation Equations. Plasma testosterone showed a significant difference over the experimental period (P < 0.001). The highest frequency of nudging and anogenital sniffing was at 08:00 h (P < 0.001); flehmen and penis unsheathed were variable (P < 0.001). The highest environmental temperature and the lowest relative humidity were registered from 14:00 to 18:00 h (P < 0.001). The highest body temperature was at 18:00 h and the lowest was at 06:00 h (P < 0.001). The highest THI >77 was recorded at 16:00 h. In conclusion, photo-stimulated bucks showed a variation of sexual behavior through 24 h/day exposed to ovariectomized females, and these sexual activities were affected by the high environmental temperature and the low relative humidity throughout the study.(AU)
Assuntos
Animais , Masculino , Ruminantes/metabolismo , Comportamento Sexual Animal/efeitos da radiação , Aclimatação/efeitos da radiaçãoRESUMO
Sheep and goat production takes place under unsuitable climate conditions, where animals are more susceptible to high temperatures. The objectives of this study were to determine, i) whether sexual behavior of photo-stimulated bucks varies through 24 h/day in March and April and, ii) whether the environmental temperature and the relative humidity affect their expression. Six bucks were submitted to artificial long days (16 h light and 8 h darkness per day/2.5 months). Bucks were exposed to ovariectomized females once a week during the non-breeding period and sexual behavior was recorded for 15 min at 2 h intervals along 24 h/day. The environmental temperature, relative humidity, temperature-humidity index (THI), and body temperature were recorded in each behavior test. Plasma testosterone, sexual behavior, environmental temperature, relative humidity, and body temperature were analyzed using Generalized Estimation Equations. Plasma testosterone showed a significant difference over the experimental period (P < 0.001). The highest frequency of nudging and anogenital sniffing was at 08:00 h (P < 0.001); flehmen and penis unsheathed were variable (P < 0.001). The highest environmental temperature and the lowest relative humidity were registered from 14:00 to 18:00 h (P < 0.001). The highest body temperature was at 18:00 h and the lowest was at 06:00 h (P < 0.001). The highest THI >77 was recorded at 16:00 h. In conclusion, photo-stimulated bucks showed a variation of sexual behavior through 24 h/day exposed to ovariectomized females, and these sexual activities were affected by the high environmental temperature and the low relative humidity throughout the study.(AU)
Assuntos
Animais , Masculino , Ruminantes/metabolismo , Comportamento Sexual Animal/efeitos da radiação , Aclimatação/efeitos da radiaçãoRESUMO
Sheep and goat production takes place under unsuitable climate conditions, where animals are more susceptible to high temperatures. The objectives of this study were to determine, i) whether sexual behavior of photo-stimulated bucks varies through 24 h/day in March and April and, ii) whether the environmental temperature and the relative humidity affect their expression. Six bucks were submitted to artificial long days (16 h light and 8 h darkness per day/2.5 months). Bucks were exposed to ovariectomized females once a week during the non-breeding period and sexual behavior was recorded for 15 min at 2 h intervals along 24 h/day. The environmental temperature, relative humidity, temperature-humidity index (THI), and body temperature were recorded in each behavior test. Plasma testosterone, sexual behavior, environmental temperature, relative humidity, and body temperature were analyzed using Generalized Estimation Equations. Plasma testosterone showed a significant difference over the experimental period (P 77 was recorded at 16:00 h. In conclusion, photo-stimulated bucks showed a variation of sexual behavior through 24 h/day exposed to ovariectomized females, and these sexual activities were affected by the high environmental temperature and the low relative humidity throughout the study.
Assuntos
Masculino , Animais , Aclimatação/efeitos da radiação , Comportamento Sexual Animal/efeitos da radiação , Ruminantes/metabolismoRESUMO
This study evaluated the occupational exposure of workers to heat during manual harvesting of coffee. The case study was conducted between May to August. Occupational heat in coffee plantations was evaluated using the Wet Bulb Globe Temperature (WBGT) method and the metabolic rate. The WBGT was obtained using the TGD 400 thermal stress meter. The determined WBGT values were compared to two standards: the Occupational Hygiene Standard (NHO) 06 and Regulatory Norm (NR) 09. For acclimatized workers, the exposure limit was not exceeded at any time during the evaluated period. Fornon-acclimatized workers, the exposure limit was not exceeded only in July.(AU)
O presente trabalhado teve como objetivo avaliar a exposição ocupacional de trabalhadores ao calor durante a colheita manual do cafeeiro. O estudo de caso foi desenvolvido entre os meses de maio a agosto. Avaliou-se o calor ocupacional em lavoura cafeeira através do método do Índice Bulbo Úmido Termômetro de Globo (IBUTG) e taxa metabólica. O IBUTG foi obtido utilizando o medidor de estresse térmico TGD 400. Os valores do IBUTG determinados foram comparados com duas normativas: Norma de Higiene Ocupacional (NHO) 06 e Norma Regulamentadora (NR) 09. Para trabalhadores aclimatizados o limite de exposição não foi superado em nenhum momento do período avaliado. Em relação aos trabalhadores não aclimatizados o limite de exposição não foi superado apenas em julho.(AU)
Assuntos
Humanos , Aclimatação/efeitos da radiação , Adaptação Fisiológica/efeitos da radiação , CaféRESUMO
This study evaluated the occupational exposure of workers to heat during manual harvesting of coffee. The case study was conducted between May to August. Occupational heat in coffee plantations was evaluated using the Wet Bulb Globe Temperature (WBGT) method and the metabolic rate. The WBGT was obtained using the TGD 400 thermal stress meter. The determined WBGT values were compared to two standards: the Occupational Hygiene Standard (NHO) 06 and Regulatory Norm (NR) 09. For acclimatized workers, the exposure limit was not exceeded at any time during the evaluated period. Fornon-acclimatized workers, the exposure limit was not exceeded only in July.
O presente trabalhado teve como objetivo avaliar a exposição ocupacional de trabalhadores ao calor durante a colheita manual do cafeeiro. O estudo de caso foi desenvolvido entre os meses de maio a agosto. Avaliou-se o calor ocupacional em lavoura cafeeira através do método do Índice Bulbo Úmido Termômetro de Globo (IBUTG) e taxa metabólica. O IBUTG foi obtido utilizando o medidor de estresse térmico TGD 400. Os valores do IBUTG determinados foram comparados com duas normativas: Norma de Higiene Ocupacional (NHO) 06 e Norma Regulamentadora (NR) 09. Para trabalhadores aclimatizados o limite de exposição não foi superado em nenhum momento do período avaliado. Em relação aos trabalhadores não aclimatizados o limite de exposição não foi superado apenas em julho.
Assuntos
Humanos , Aclimatação/efeitos da radiação , Adaptação Fisiológica/efeitos da radiação , CaféRESUMO
The aim of this study was to evaluate the efficiency of the load wetting method to attenuate the ambience of the load the transport of broilers. Fourteen commercial consignments were monitored over a 25 km route, and in seven of these, the load wetting was carried (LW) out while in the other seven no wetting was done (LD). The temperatures of the side, top and rear load boxes were analyzed by infrared thermography. The central row load boxes were evaluated by geostatistics, using temperature variability (TA), relative humidity (RH) and the enthalpy comfort index (ECI). The mean was compared by Student's t-test (P < 0.05). The results showed that load wetting has a momentary effect (P < 0.05). The boxes located in the central rows in the LW showed a higher (P < 0.05) ECI compared to those in the LD. Inaddition, areas classified as lethal were formed in the LW. In conclusion, load wetting was not an efficient method to attenuate the ambience of load during the commercial transport of broilers, as it only has momentary and transient effects.(AU)
Assuntos
Animais , Galinhas , Produtos Avícolas/economia , Aclimatação/efeitos da radiaçãoRESUMO
The aim of this study was to evaluate the efficiency of the load wetting method to attenuate the ambience of the load the transport of broilers. Fourteen commercial consignments were monitored over a 25 km route, and in seven of these, the load wetting was carried (LW) out while in the other seven no wetting was done (LD). The temperatures of the side, top and rear load boxes were analyzed by infrared thermography. The central row load boxes were evaluated by geostatistics, using temperature variability (TA), relative humidity (RH) and the enthalpy comfort index (ECI). The mean was compared by Student's t-test (P < 0.05). The results showed that load wetting has a momentary effect (P < 0.05). The boxes located in the central rows in the LW showed a higher (P < 0.05) ECI compared to those in the LD. Inaddition, areas classified as lethal were formed in the LW. In conclusion, load wetting was not an efficient method to attenuate the ambience of load during the commercial transport of broilers, as it only has momentary and transient effects.
Assuntos
Animais , Aclimatação/efeitos da radiação , Galinhas , Produtos Avícolas/economiaRESUMO
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.
Assuntos
Aclimatação/efeitos da radiação , Flavodoxina/genética , Regulação da Expressão Gênica de Plantas/efeitos da radiação , Luz , Nicotiana/metabolismo , Fotossíntese/efeitos da radiação , Folhas de Planta/genética , Relação Dose-Resposta à Radiação , Fenótipo , Folhas de Planta/efeitos da radiação , Nicotiana/genética , Nicotiana/fisiologia , Nicotiana/efeitos da radiaçãoRESUMO
Polymeric nanoparticles have emerged as carrier systems for molecules that release nitric oxide (NO), a free radical involved in plant stress responses. However, to date, nanoencapsulated NO donors have not been applied to plants under realistic field conditions. Here, we verified the effects of free and nanoencapsulated NO donor, S-nitroso-mercaptosuccinic acid (S-nitroso-MSA), on growth, physiological and biochemical parameters of neotropical tree seedlings kept under full sunlight in the nursery for acclimation. S-nitroso-MSA incorporation into chitosan nanoparticles partially protected the NO donor from thermal and photochemical degradation. The application of nanoencapsulated S-nitroso-MSA in the substrate favoured the growth of seedlings of Heliocarpus popayanensis, a shade-intolerant tree. In contrast, free S-nitroso-MSA or nanoparticles containing non-nitrosated mercaptosuccinic acid reduced photosynthesis and seedling growth. Seedlings of Cariniana estrellensis, a shade-tolerant tree, did not have their photosynthesis and growth affected by any formulations, despite the increase of foliar S-nitrosothiol levels mainly induced by S-nitroso-MSA-loaded nanoparticles. These results suggest that depending on the tree species, nanoencapsulated NO donors can be used to improve seedling acclimation in the nursery.
Assuntos
Aclimatação , Nanopartículas/metabolismo , Doadores de Óxido Nítrico/administração & dosagem , Doadores de Óxido Nítrico/farmacocinética , Óxido Nítrico/farmacocinética , Plântula/metabolismo , Luz Solar , Aclimatação/efeitos dos fármacos , Aclimatação/fisiologia , Aclimatação/efeitos da radiação , Portadores de Fármacos , Composição de Medicamentos , Liberação Controlada de Fármacos , Jardins , Nanopartículas/química , Doadores de Óxido Nítrico/farmacologia , Fotossíntese/fisiologia , Folhas de Planta/efeitos dos fármacos , Folhas de Planta/metabolismo , Folhas de Planta/efeitos da radiação , S-Nitrosotióis/administração & dosagem , S-Nitrosotióis/química , S-Nitrosotióis/farmacocinética , S-Nitrosotióis/farmacologia , Plântula/efeitos dos fármacos , Plântula/crescimento & desenvolvimento , Tiomalatos/administração & dosagem , Tiomalatos/farmacocinética , Tiomalatos/farmacologia , Árvores/efeitos dos fármacos , Árvores/metabolismo , Árvores/efeitos da radiação , Clima TropicalRESUMO
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.
Assuntos
Regulação da Expressão Gênica de Plantas/efeitos da radiação , Redes Reguladoras de Genes , Luz , Aclimatação/fisiologia , Aclimatação/efeitos da radiação , Clorofila/metabolismo , Fluorescência , Redes Reguladoras de Genes/efeitos da radiação , Fotossíntese/efeitos da radiação , Folhas de Planta/fisiologia , Folhas de Planta/efeitos da radiação , Transpiração Vegetal/efeitos da radiação , Análise de Componente PrincipalRESUMO
The influence of extremely low frequency electromagnetic fields on net photosynthesis, transpiration, photosynthetic pigment concentration, and gene expression of ribulose 1,5-bisphosphate carboxylase/oxygenase small subunit (RBCS1), during in vitro establishment, in vitro multiplication and acclimatization phases of coffee seedlings were investigated. Untreated coffee plants were considered as control, whereas treated plants were exposed to a 60 Hz sinusoidal magnetic field of 2 mT of magnetic induction during 3 min. This magnetic field was generated by an electromagnet, connected to a wave generator. The results revealed that magnetically treated plants showed a significant increase in net photosynthesis (85.4% and 117.9%, in multiplication and acclimatization phases, respectively), and in photosynthetic pigment concentration (66.6% for establishment phase, 79.9% for multiplication phase, and 43.8% for acclimatization phase). They also showed a differential RBCS1 gene expression (approximately twofold) and a decrease of transpiration rates in regard to their control plants. In conclusion, the findings suggest that the application of 60 Hz magnetic field to in vitro coffee plants may improve the seedlings quality by modifying some photosynthetic physiological and molecular processes, increasing their vigor, and ensuring better plant development in later stages.
Assuntos
Coffea/fisiologia , Coffea/efeitos da radiação , Campos Magnéticos , Plântula/fisiologia , Plântula/efeitos da radiação , Aclimatação/fisiologia , Aclimatação/efeitos da radiação , Clorofila/metabolismo , Expressão Gênica/fisiologia , Expressão Gênica/efeitos da radiação , Magnetismo , Microscopia Eletrônica de Varredura , Periodicidade , Fotossíntese/fisiologia , Fotossíntese/efeitos da radiação , Proteínas de Plantas/metabolismo , Transpiração Vegetal/fisiologia , Transpiração Vegetal/efeitos da radiaçãoRESUMO
Coffee (Coffea arabica L.) has been traditionally considered as shade-demanding, although it performs well without shade and even out-yields shaded coffee. Here we investigated how coffee plants adjust their metabolic machinery to varying light supply and whether these adjustments are supported by a reprogramming of the primary and secondary metabolism. We demonstrate that coffee plants are able to adjust its metabolic machinery to high light conditions through marked increases in its antioxidant capacity associated with enhanced consumption of reducing equivalents. Photorespiration and alternative pathways are suggested to be key players in reductant-consumption under high light conditions. We also demonstrate that both primary and secondary metabolism undergo extensive reprogramming under high light supply, including depression of the levels of intermediates of the tricarboxylic acid cycle that were accompanied by an up-regulation of a range of amino acids, sugars and sugar alcohols, polyamines and flavonoids such as kaempferol and quercetin derivatives. When taken together, the entire dataset is consistent with these metabolic alterations being primarily associated with oxidative stress avoidance rather than representing adjustments in order to facilitate the plants from utilizing the additional light to improve their photosynthetic performance.
Assuntos
Aclimatação/efeitos da radiação , Coffea/metabolismo , Coffea/efeitos da radiação , Luz , Estresse Oxidativo/efeitos da radiação , Fotossíntese/efeitos da radiação , Dióxido de Carbono/metabolismo , Clorofila/metabolismo , Fluorescência , Metabolômica , Nitratos/metabolismo , Nitrogênio/metabolismo , Nucleotídeos/metabolismo , Folhas de Planta/anatomia & histologia , Folhas de Planta/efeitos da radiação , Metabolismo Secundário/efeitos da radiação , Amido/metabolismo , TermodinâmicaRESUMO
Light and water are important factors that may limit the growth and development of higher plants. The aim of this study was to evaluate photosynthetic parameters and growth in seedlings of Bertholletia excelsa and Carapa guianensis in response to pre-acclimation to full sunlight and mild water stress. I used six independent pre-acclimation treatments (0, 90 (11h15-12h45), 180 (10h30-13h30), 360 (09h00-15h00), 540 (07h30-16h30) and 720 min (06h00-18h00)) varying the time of exposure to full sunlight (PFS) during 30 days, followed by whole-day outdoor exposure for 120 days. Before PFS, the plants were kept in a greenhouse at low light levels (0.8 mol m-2 day-1). The PFS of 0 min corresponded to plants constantly kept under greenhouse conditions. From the beginning to the end of the experiment, each PFS treatment was submitted to two water regimes: moderate water stress (MWS, pre-dawn leaf water potential (L) of -500 to -700 kPa) and without water stress (WWS, L of -300 kPa, soil kept at field capacity). Plants under MWS received only a fraction of the amount of water applied to the well-watered ones. At the end of the 120-day-period under outdoor conditions, I evaluated light saturated photosynthesis (Amax), stomatal conductance (g s), transpiration (E) and plant growth. Both Amax and g s were higher for all plants under the PFS treatment. Stem diameter growth rate and Amax were higher for C. guianensis subjected to MWS than in well-watered plants. The contrary was true for B. excelsa. The growth of seedlings was enhanced by exposure to full sunlight for 180 minutes in both species. However, plants of B. excelsa were sensitive to moderate water stress. The higher photosynthetic rates and faster growth of C. guianensis under full sun and moderate water stress make this species a promissory candidate to be tested in reforestation programs.(AU)
A luz e a água são importantes fatores que limitam o crescimento e o desenvolvimento das plantas. O objetivo deste estudo foi avaliar os paâmetros fotossintéticos e o crescimento em mudas de Bertholletia excelsa e Carapa guianensis em resposta a pré-aclimatação à luz solar plena e estresse hídrico moderado. Foram usados seis independentes tratamentos de pré-aclimatação a pleno sol (PFS), sendo estes de (0, 90 (11h15-12h45), 180 (10h30-13h30), 360 (09h00-15h00), 540 (07h30-16h30) e 720 min (06h00-18h00)) durante 30 dias seguidos por um período de exposição a pleno sol de 120 dias durante o dia todo. Antes da PFS, as plantas foram mantidas em casa de vegetação a baixos níveis de luz (0,8 mol m-2 dia-1). O PFS de 0 min correspondeu às plantas mantidas constatemente na casa de vegetação. Cada tratamento de PFS foi submetido desde o início até o final do experimento a dois regimes hídricos, denominado de estresse hídrico moderado (MWS, potencial hidrico da folha medido antes do amanhecer (ΨL) de -500 a -700 kPa) e sem estresse hídrico (WWS , ΨL de -300 kPa, solo mantido na capacidade de campo). As plantas do tratamento MWS receberam apenas uma fração do volume de água fornecido para aquelas do tratamento WWS. No final do período de 120 dias foi avaliada a fotossíntese saturada por luz (Amax), a condutância estomática (gs), transpiração (E) e o crescimento. Amax e gs foram maiores em todas as plantas sob o tratamento de PFS. A taxa de crescimento em diâmetro e Amax foram maiores em plantas de C. guianensis submetidas à MWS. O contrário foi observado em B. excelsa. O crescimento das mudas foi maior nas plantas expostas à luz solar em 180 minutos em ambas as espécies. Entretanto, as plantas de B. excelsa foram mais sensíveis ao estresse hídrico moderado. C. guianensis foi à especie que teve melhor desempenho fotossintético e crescimento sob estresse hídrico moderado e luz solar plena...(AU)
Assuntos
Fotossíntese , Bertholletia/crescimento & desenvolvimento , Bertholletia/efeitos da radiação , Aclimatação/efeitos da radiação , Desidratação , Plantas/efeitos da radiaçãoRESUMO
Light and water are important factors that may limit the growth and development of higher plants. The aim of this study was to evaluate photosynthetic parameters and growth in seedlings of Bertholletia excelsa and Carapa guianensis in response to pre-acclimation to full sunlight and mild water stress. I used six independent pre-acclimation treatments (0, 90 (11h15-12h45), 180 (10h30-13h30), 360 (09h00-15h00), 540 (07h30-16h30) and 720 min (06h00-18h00)) varying the time of exposure to full sunlight (PFS) during 30 days, followed by whole-day outdoor exposure for 120 days. Before PFS, the plants were kept in a greenhouse at low light levels (0.8 mol m-2 day-1). The PFS of 0 min corresponded to plants constantly kept under greenhouse conditions. From the beginning to the end of the experiment, each PFS treatment was submitted to two water regimes: moderate water stress (MWS, pre-dawn leaf water potential (L) of -500 to -700 kPa) and without water stress (WWS, L of -300 kPa, soil kept at field capacity). Plants under MWS received only a fraction of the amount of water applied to the well-watered ones. At the end of the 120-day-period under outdoor conditions, I evaluated light saturated photosynthesis (Amax), stomatal conductance (g s), transpiration (E) and plant growth. Both Amax and g s were higher for all plants under the PFS treatment. Stem diameter growth rate and Amax were higher for C. guianensis subjected to MWS than in well-watered plants. The contrary was true for B. excelsa. The growth of seedlings was enhanced by exposure to full sunlight for 180 minutes in both species. However, plants of B. excelsa were sensitive to moderate water stress. The higher photosynthetic rates and faster growth of C. guianensis under full sun and moderate water stress make this species a promissory candidate to be tested in reforestation programs.
A luz e a água são importantes fatores que limitam o crescimento e o desenvolvimento das plantas. O objetivo deste estudo foi avaliar os paâmetros fotossintéticos e o crescimento em mudas de Bertholletia excelsa e Carapa guianensis em resposta a pré-aclimatação à luz solar plena e estresse hídrico moderado. Foram usados seis independentes tratamentos de pré-aclimatação a pleno sol (PFS), sendo estes de (0, 90 (11h15-12h45), 180 (10h30-13h30), 360 (09h00-15h00), 540 (07h30-16h30) e 720 min (06h00-18h00)) durante 30 dias seguidos por um período de exposição a pleno sol de 120 dias durante o dia todo. Antes da PFS, as plantas foram mantidas em casa de vegetação a baixos níveis de luz (0,8 mol m-2 dia-1). O PFS de 0 min correspondeu às plantas mantidas constatemente na casa de vegetação. Cada tratamento de PFS foi submetido desde o início até o final do experimento a dois regimes hídricos, denominado de estresse hídrico moderado (MWS, potencial hidrico da folha medido antes do amanhecer (ΨL) de -500 a -700 kPa) e sem estresse hídrico (WWS , ΨL de -300 kPa, solo mantido na capacidade de campo). As plantas do tratamento MWS receberam apenas uma fração do volume de água fornecido para aquelas do tratamento WWS. No final do período de 120 dias foi avaliada a fotossíntese saturada por luz (Amax), a condutância estomática (gs), transpiração (E) e o crescimento. Amax e gs foram maiores em todas as plantas sob o tratamento de PFS. A taxa de crescimento em diâmetro e Amax foram maiores em plantas de C. guianensis submetidas à MWS. O contrário foi observado em B. excelsa. O crescimento das mudas foi maior nas plantas expostas à luz solar em 180 minutos em ambas as espécies. Entretanto, as plantas de B. excelsa foram mais sensíveis ao estresse hídrico moderado. C. guianensis foi à especie que teve melhor desempenho fotossintético e crescimento sob estresse hídrico moderado e luz solar plena...
Assuntos
Aclimatação/efeitos da radiação , Bertholletia/crescimento & desenvolvimento , Bertholletia/efeitos da radiação , Desidratação , Fotossíntese , Plantas/efeitos da radiaçãoRESUMO
Mountain pastures dominated by the pasture grass Setaria sphacelata in the Andes of southern Ecuador are heavily infested by southern bracken (Pteridium arachnoideum), a major problem for pasture management. Field observations suggest that bracken might outcompete the grass due to its competitive strength with regard to the absorption of photosynthetically active radiation (PAR). To understand the PAR absorption potential of both species, the aims of the current paper are to (1) parameterize a radiation scheme of a two-big-leaf model by deriving structural (LAI, leaf angle parameter) and optical (leaf albedo, transmittance) plant traits for average individuals from field surveys, (2) to initialize the properly parameterized radiation scheme with realistic global irradiation conditions of the Rio San Francisco Valley in the Andes of southern Ecuador, and (3) to compare the PAR absorption capabilities of both species under typical local weather conditions. Field data show that bracken reveals a slightly higher average leaf area index (LAI) and more horizontally oriented leaves in comparison to Setaria. Spectrometer measurements reveal that bracken and Setaria are characterized by a similar average leaf absorptance. Simulations with the average diurnal course of incoming solar radiation (1998-2005) and the mean leaf-sun geometry reveal that PAR absorption is fairly equal for both species. However, the comparison of typical clear and overcast days show that two parameters, (1) the relation of incoming diffuse and direct irradiance, and (2) the leaf-sun geometry play a major role for PAR absorption in the two-big-leaf approach: Under cloudy sky conditions (mainly diffuse irradiance), PAR absorption is slightly higher for Setaria while under clear sky conditions (mainly direct irradiance), the average bracken individual is characterized by a higher PAR absorption potential. (approximately 74 MJ m(-2) year(-1)). The latter situation which occurs if the maximum daily irradiance exceeds 615 W m(-2) is mainly due to the nearly orthogonal incidence of the direct solar beam onto the horizontally oriented frond area which implies a high amount of direct PAR absorption during the noon maximum of direct irradiance. Such situations of solar irradiance favoring a higher PAR absorptance of bracken occur in approximately 36% of the observation period (1998-2005). By considering the annual course of PAR irradiance in the San Francisco Valley, the clear advantage of bracken on clear days (36% of all days) is completely compensated by the slight but more frequent advantage of Setaria under overcast conditions (64% of all days). This means that neither bracken nor Setaria show a distinct advantage in PAR absorption capability under the current climatic conditions of the study area.
Assuntos
Ecossistema , Luz , Modelos Biológicos , Fotossíntese/fisiologia , Pteridium/efeitos da radiação , Setaria (Planta)/efeitos da radiação , Absorção , Aclimatação/fisiologia , Aclimatação/efeitos da radiação , Equador , Geografia , Fotossíntese/efeitos da radiação , Folhas de Planta/crescimento & desenvolvimento , Folhas de Planta/metabolismo , Folhas de Planta/efeitos da radiação , Pteridium/crescimento & desenvolvimento , Pteridium/metabolismo , Setaria (Planta)/crescimento & desenvolvimento , Setaria (Planta)/metabolismo , Fatores de TempoRESUMO
Photoacclimation of photosynthesis was investigated in a tropical population of C. glomerata (São Paulo State, southeastern Brazil, 20 degrees 48' 24" S and 49 degrees 22' 24" W) by chlorophyll fluorescence parameters and chlorophyll a content. Plants were acclimated to two levels of irradiance: low (65 +/- 5 micromol.m(-2).s(-1)) and high (300 +/- 10 micromol.m(-2).s(-1)) and exposed short-term (4 days) and long-term (28 days) under a light-dark cycle of 12:12 hours. Photosynthesis-irradiance (PI) curves revealed distinct strategies of photoacclimation. In long-term exposure, plants acclimated by altering the photosynthetic units (PSU) number and keeping fixed the PSU size, revealed by increased rates of maximum photosynthesis (Pmax), lower photosynthetic efficiency (alpha) and higher values of the saturation parameter (Ik) under high irradiance. The short-term acclimation strategy consisted of changing the PSU size, with a fixed number of PSUs, as revealed by similar Pmax but higher alpha and lower Ik under low irradiance. Chlorophyll a contents followed the general pattern reported in green algae of higher concentrations under lower irradiance. Dark/light induction curves revealed consistently higher values of potential quantum yield under low irradiance. Initial and final values showed a higher recovery capacity in the short (84.4-90.6%) term exposure than in the long-term case (81.4-81.5%). ETR (electron transport rate) and NPQ (non-photochemical quenching) values were consistently higher under low irradiance. ETR showed a continuous and steady increase along the light exposure period in the short and long-term experiments, whereas NPQ values revealed a rapid increase after 15 seconds of light exposure, kept a slightly increasing trend and stabilized in most treatments. Lower photosynthetic performance (ETR) and recovery capacity of potential quantum yield were observed, particularly in long-term exposure, suggesting that this population is constrained by the typical high light environment of tropical regions.
Assuntos
Aclimatação/fisiologia , Clorofila/análise , Clorófitas/fisiologia , Fotossíntese/fisiologia , Luz Solar , Aclimatação/efeitos da radiação , Clorófitas/efeitos da radiação , Fotoperíodo , Fotossíntese/efeitos da radiação , Espectrometria de Fluorescência , Temperatura , Clima TropicalRESUMO
Photoacclimation of photosynthesis was investigated in a tropical population of C. glomerata (São Paulo State, southeastern Brazil, 20º 48 24" S and 49º 22 24" W) by chlorophyll fluorescence parameters and chlorophyll a content. Plants were acclimated to two levels of irradiance: low (65 ± 5 µmol.m-2.s-1) and high (300 ± 10 µmol.m-2.s-1) and exposed short-term (4 days) and long-term (28 days) under a light-dark cycle of 12:12 hours. Photosynthesis-irradiance (PI) curves revealed distinct strategies of photoacclimation. In long-term exposure, plants acclimated by altering the photosynthetic units (PSU) number and keeping fixed the PSU size, revealed by increased rates of maximum photosynthesis (Pmax), lower photosynthetic efficiency (alpha) and higher values of the saturation parameter (Ik) under high irradiance. The short-term acclimation strategy consisted of changing the PSU size, with a fixed number of PSUs, as revealed by similar Pmax but higher alpha and lower Ik under low irradiance. Chlorophyll a contents followed the general pattern reported in green algae of higher concentrations under lower irradiance. Dark/light induction curves revealed consistently higher values of potential quantum yield under low irradiance. Initial and final values showed a higher recovery capacity in the short (84.4-90.6 percent) term exposure than in the long-term case (81.4-81.5 percent). ETR (electron transport rate) and NPQ (non-photochemical quenching) values were consistently higher under low irradiance. ETR showed a continuous and steady increase along the light exposure period in the short and long-term experiments, whereas NPQ values revealed a rapid increase after 15 seconds of light exposure, kept a slightly increasing trend and stabilized in most treatments. Lower photosynthetic performance (ETR) and recovery capacity of potential quantum yield were observed, particularly in long-term exposure, suggesting that this population...
A fotoaclimatação da fotossíntese foi investigada numa população tropical de Cladophora glomerata (Estado de São Paulo, sudeste do Brasil, 20º 48 24" S e 49º 22 24" W) através de parâmetros de fluorescência da clorofila e conteúdo de clorofila a. As plantas foram aclimatadas a dois níveis de irradiância: baixa (65 ± 5 µmol.m-2.s-1) e alta (300 ± 10 :mol.m-2.s-1) e expostas a curto período (4 dias) e longo período (28 dias) em fotoperíodo de 12 horas. Curvas de fotossíntese-irradiância (FI) revelaram estratégias distintas de fotoaclimatação. Plantas expostas a longo período aclimataram pela alteração do número de unidades fotossintéticas (UF) e mantiveram fixo o tamanho das UF. Estas características foram reveladas por menores taxas de fotossíntese máxima (Fmax), menor eficiência fotossintética (alfa) e valores mais altos do parâmetro de saturação (Ik) em alta irradiância. A estratégia de aclimatação em curto período consistiu em mudança no tamanho das UF, com número fixo de UF, conforme revelado por taxas semelhantes de fotossíntese máxima (Fmax), maiores valores de alfa e menores de Ik em baixa irradiância. Os conteúdos de clorofila a seguiram o padrão geral reportado para algas verdes de maiores concentrações em baixa irradiância. Curvas de indução escuro/luz revelaram valores consistentemente mais elevados de rendimento quântico potencial em baixa irradiância. Valores iniciais e finais mostraram capacidade de recuperação mais elevada em curto período (84,4-90,6 por cento) do que em longo período (81,4-81,5 por cento). Os valores da taxa de transporte de elétrons (ETR) e extinção não-fotoquímica (NPQ) foram consistentemente mais elevados em baixa irradiância. Os valores de ETR tiveram aumento contínuo e estável ao longo do período de exposição luminosa em curto e longo períodos, enquanto que os de NPQ revelaram aumento rápido após 15 seconds de exposição à luz, mantiveram leve tendência de aumento e então estabilizaram...
Assuntos
Aclimatação/fisiologia , Clorófitas/fisiologia , Clorofila/análise , Fotossíntese/fisiologia , Luz Solar , Aclimatação/efeitos da radiação , Clorófitas/efeitos da radiação , Fotoperíodo , Fotossíntese/efeitos da radiação , Espectrometria de Fluorescência , Temperatura , Clima TropicalRESUMO
Three high-yielding wheat genotypes (T. aestivum L., c.v. Siete Cerros, Seri and Bacanora, released in 1966, 1982 and 1988, respectively) were grown under irrigation in two high radiation, low relative humidity environments (Tlaltizapan and Ciudad Obregon CIMMYT experimental stations, Mexico). Gas exchange and fluorescence parameters were assessed on the flag leaf during the day. Carbon isotope discrimination (delta) was analysed in flag leaf at anthesis and in grain at maturity. In both environments, gas exchange and fluorescence parameters varied markedly with irradiance and temperature. Analysis of their respective variation indicated the occurrence of photo-respiration and photo-inhibition, particularly in Tlaltizapan, the warmest environment, and in Siete Cerros. In Ciudad Obregon (high-yielding environment) lower Ci (internal CO2 concentration) and delta La (carbon isotope discrimination of the leaf) suggested a higher intrinsic photosynthetic capacity in the variety Bacanora. Higher yield of this genotype was also associated with higher Fv'/Fo' (ratio of photochemical and non photochemical rate constants in the light) and Fm'/Fm (ratio of the non photochemical rate constants in the dark and light adapted state).