The physiological process of cold acclimation protects plants native to the temperate regions of the world from the deleterious effects of low and freezing temperatures. This is achieved by a series of transcriptional, regulatory, and metabolic changes that enable continued growth and survival. Within minutes of exposure to temperatures below ca. 10°C, a complex cascade of transcriptional events is initiated to accomplish these changes. The initial alarm phase favors the rapid induction of a library of stress proteins with protective functions (e.g. COR proteins). This is followed by a cold hardened phase, characterized by maximal freezing tolerance, which continues until either the stress is removed, or the plant's metabolic and/or developmental state can no longer support maximal resistance. We have studied some of the important transcription factors and transcriptional changes associated with the initial alarm and later hardened phases of cold acclimation in the herbaceous annual Arabidopsis thaliana and the woody perennial Populus spp. We confirmed the functionality of the CBF-mediated signaling cascade in Poplar overexpressing AtCBF1, but noted that regulon composition and endogenous poplar CBF ortholog induction appeared to be tissue-specific. The lack of statistically significant DRE enrichment in the Poplar AtCBF1 regulons led us to investige cis-element abundance in the cold-associated transcription factor regulons of publicly available microarray data from Arabidopsis, leading to the development of a gene voting method of microarray analysis that we used to test for regulatory associations between transcription factors and their downstream cis-elements and gene targets. This analysis resulted in a new transcriptional model of the ICE1-mediated signaling cascade and implicated a role for phytochrome A. Application of this same method to microarray data from arabidopsis leaves developed at low temperature allowed us to identify a new cis-element, called DDT, which possessed enhancer-blocking function during the alarm stage of cold stress, but was enriched in the promoters of genes upregulated during the later cold hardened stages. As leaf growth and development at low temperature correlated with the enhancement freeze tolerance in Arabidopsis, we compared the transcriptomes of rapidly growing and fully grown poplar leaves at night (when both low temperatures and PhyA status might play important roles in nature), in the hopes of comparing this data with that of cold-treated leaves in the future. We identified the nocturnal mode of leaf growth in Populus deltoides as predominantly proliferative as opposed to expansive, and potentially linked to cellular carbohydrate status.

Išstudijavus mokslinius literatūros šaltinius, pastebėta, kad kūno temperatūros, o tuo pačiu ir raumens vidinės temperatūros padidėjimas sukelia daug fiziologinių reakcijų žmogaus organizme, tačiau vis dar mažai darbų, nagrinėjančių aklimacijos (aklimacija �� tai dirbtinėse sąlygose (laboratorijoje) sukelta ilgalaikė aklimatizacija) hipertermijai, sukeltos dirbtiniu būdu, poveikį žmogaus fiziologinių rodiklių kaitai, raumens išvystomai maksimaliai valingai jėgai. Nepavyko rasti duomenų kaip maksimalios valingos jėgos metu keičiasi raumenų elektrinis aktyvumas, priklausantis nuo aklimacijos hipertermijai. Pagrindinis šio darbo tikslas buvo nustatyti ir įvertinti dirbtinės aklimacijos hipertermijai poveikį �����mogaus organizmui. Uždaviniai: Nustatyti ir įvertinti žmogaus fiziologinių rodiklių (rektalinę, odos bei kūno temperatūras, fiziologinį stresą, netenkamą kūno svorį, širdies susitraukimų dažnį ir šiluminį stresą) kaitą aklimacijos hipertermijai laikotarpyje: prieš pasyvų šildymą, šildymo metu ir po šildymo; nustatyti aklimacijos hipertermijai poveikį raumenų atsparumui nuovargiui; nustatyti aklimacijos hipertermijai poveikį raumenų centriniam aktyvacijos koeficientui; nustatyti ir įvertinti aklimacijos hipertermijai poveikį šlaunies raumens elektriniam aktyvumui. Šio tyrimo metu iš viso buvo atliekami aštuoni tyrimai — vienas kontrolinis ir septyni hipertermiją sukeliantys eksperimentiniai. Eksperimentiniai nuo kontrolinio skyrėsi pasyviu kojų pašildymu (tiriamieji... [toliau žr. visą tekstą] / Firstly, it is important to emphasize that the research of different scientific articles and other sources of information has proved that the increment of temperature in the man’s body as well as the inner muscle causes many physiologic reflexes in human’s organism. However not many research projects analyzing the impact of the acclimation (In vitro(in laboratory) related long term acclimatization) to hyperthermic environment, created in imitative way, neither on the fluctuation of man’s vital functions nor on the maximum voluntary muscle strength, could be found. Secondly, it should be noted, that none of the above mentioned sources provided the information on the change of muscle electric activity at the moment of its maximum voluntary strength. Therefore, the main purpose of this research was to establish and measure the influence of the imitative acclimation of hyperthermia on the man’s body. The main tasks of the project were to observe and evaluate the change of man’s physiological functions (rectal, skin and body temperature, physiologic stress, weight loss, heart rate and thermic stress) during the acclimation to hyperthermia process: before passive heating, during the heating time and after it; to establish the impact of acclimation to hyperthermia on the maximum voluntary force as well as on the maximum activation rate; to establish and measure the impact of the acclimation to hyperthermia on the muscle electrical activity. In order to achieve the desired... [to full text]

Žmogaus adaptacija prie karščio yra visapusiškai nagrinėjama ir plati problema (Hori, 1978). Literatūroje gausu tyrimų, nagrinėjančių hipertermijos poveikį neuroraumeninei funkcijai po fizinių pratimų karštyje (Nybo & Nielsen, 2001) ar pasyvaus šildymo (Thomas et al., 2006; Todd et al., 2005). M. M. Thomas et al. (2006) nustatė, kad pasyvaus šildymo metu, padidinus vidinę kūno temperatūrą iki 39,5 oC, sumažėja maksimali izometrinė pėdos lenkiamųjų raumenų jėga ir tai įtakoja raumenų aktyvacijos iš CNS sumažėjimas. Anksčiau atlikti tyrimai patvirtina, kad aukšta organizmo vidinė temperatūra paveikia CNS ir jos galimybę aktyvuoti dirbančius raumenis (Nybo & Nielsen, 2001; Todd et al., 2005). Organizmui aklimuojantis prie karščio, sumažėja TREKT, ŠSD, FSI ir padidėja prakaitavimas, kas lemia mažesnį fiziologinį-terminį stresą hipertermijos sąlygomis (Brazaitis ir kt., 2009; Brazaitis ir Skurvydas, 2010), tačiau sunku rasti tyrimų, nagrinėjančių kaip tai paveikia neuroraumeninę funkciją. M. Brazaitis ir A. Skurvydas (2010) nustatė, kad po 7 pasyvaus šildymo procedūrų (~44 oC vandenyje po 45 minutes), kurios buvo vykdomos kas antrą dieną 2 savaičių laikotarpyje, organizmas aklimavosi prie karščio, bet tai nepaveikė centrinio ir periferinio nuovargio MVJ-2min izometrinio krūvio metu hipertermijos sąlygomis. Mūsų atliktame tyrime buvo naudota unikali pasyvaus šildymo metodika (siekiama TREKT padidinti iki 39,5 0C, maksimalus šildymo procedūros laikas 120 min., šildymo procedūros... [toliau žr. visą tekstą] / Human adaptation to heat is comprehensive of a broad problem (Hori, 1978). The literature is rich in research of analyzing the influence of hyperthermia on neuromuscular function, after exercising in the heat (Nybo & Nielsen, 2001) or passive heating (Thomas et al., 2006; Todd et al., 2005). M. M. Thomas et al. (2006) ascertained that the increase to 39,5 oC of core temperature in passive heating, reduces maximal isometric force of plantar flexors and this is influence of the reduction on voluntary muscle activation from CNS. Earlier studies show, that high core temperature affects CNS and its ability to activate working muscles (Nybo & Nielsen, 2001; Todd et al., 2005). Heat acclimation occurs with reduced rectal temperature, heart rate, physiological strain index and increased sweat rate, which causes reduction in physiological-thermal stress in the hyperthermia (Brazaitis ir kt., 2009; Brazaitis ir Skurvydas, 2010), but it is difficult to find studies how this affects the neuromuscular function. M. Brazaitis & A. Skurvydas (2010) found out that after 7 passive heating procedures (in ~44 oC water, 45 minutes each), which was carried out every second day for two weeks, heat acclimation occurred, but did not change the central and peripheral fatigue during a 2-min MVC in hyperthermia. In our study, we used the unique passive heating technique (we tried to elevate rectal temperature to 39,5 0C, maximal passive heating time was 120 min., 16 days of passive heating procedure... [to full text]

Climate change is now widely regarded as the single greatest threat to coral reefs. Climate change poses a range of different threats and reef ecosystems are widely reported as being amongst the first ecosystems to be severely affected by increases in global average temperatures. Coral reef managers responding effectively to the climate change threat will require research and monitoring, communication, impact mitigation and informed planning. Aspects of this thesis cover all of those working areas.

Made available in DSpace on 2015-03-26T13:36:41Z (GMT). No. of bitstreams: 1 texto completo.pdf: 1212166 bytes, checksum: 3f37e080ab7fd33c90b19c34980f54cb (MD5) Previous issue date: 2011-02-16 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / The present study was carried out in order to analyse the contributions of hydraulic, diffusive (stomatal and mesophilic) and biochemical limitations to photosynthesis in coffee, the nitrogen partitioning within the photosynthetic machinery as well as its activation state in response to light. To this end, arabica coffee (Coffea arabica L.) plants were grown in pots during 12 months under two light availabilities (0 and 90% shading). Compared to sun plants, shade plants showed higher specific leaf area (63%), chlorophyll (76%), carotenoids (62%) and nitrogen (N) (15%) mass-based concentrations, as well as higher chlorophyll/N ratio (53%); in contrast, shade plants showed lower stomatal density (32%), stomatal index (20%), venation density (27%), stomatal (27%) and mesophyll (37%) conductance and N concentration on an area basis (30%). There were no differences in pigment concentrations (on an area basis) or in the chlorophyll a/b ratio between treatments. The N partitioning invested in Rubisco and electron transport chain components differed little between the phenotypes; however, higher N fraction was invested in structural components (13%) in shade plants compared to sun plants. There were no differences in mass-based gas exchange parameters except for the maximum carboxylation velocity calculated on a Cc basis, 24% higher in shade plants than in sun plants. In contrast, on an area basis, sun plants exhibited higher maximum carboxylation velocity (32%), maximum photosynthetic rate (45%) and electron transport rate (43%). Apparently, mesophyll conductance may be of equal or less importance than stomal conductance to explain the low photosynthetic rates in coffee, regardless of growth irradiance. It is suggested that the hydraulic architecture is the most limiting primary factor to photosynthesis in coffee plants. The results support the hypothesis that shade plants would take better advantage of sunflecks energy in relation to sun plants as a result of having higher activation states and lower induction losses, in addition to absence of photoinhibition in the shade leaves. The results help to explain, in part, the low photosynthetic nitrogen-use efficiency, as a consequence of high investment of N into non-photossynthetic components. / O presente estudo foi conduzido procurando-se analisar as contribuições das limitações hidráulicas, difusivas (estomática e mesofílica) e bioquímicas à fotossíntese do cafeeiro, a partição do nitrogênio dentro da maquinaria fotossintética e a ativação desta maquinaria em resposta à irradiância. Para tal, plantas de café arábica (Coffea arabica L.) foram cultivadas em vasos durante 12 meses, sob duas intensidades lumínicas (0 e 90% de sombreamento). Comparadas com as plantas de sol, as plantas à sombra exibiram maiores área foliar específica (63%), concentrações (em base de massa) de clorofilas (76%), carotenóides (62%) e de nitrogênio (N) (15%), como também maior razão clorofilas/N (53%); em contraste, as plantas sombreadas exibiram menores densidade estomática (32%), índice estomático (20%), densidade de venação (27%), condutâncias estomática (27%) e mesofílica (37%) e concentração de N em base de área (30%). Não houve variações significativas nas concentrações de pigmentos em base de área e na razão clorofila a/b entre os tratamentos. A partição do N investido em Rubisco e em componentes envolvidos no transporte de elétrons pouco diferiu entre os fenótipos; porém, maior fração do N investida em componentes estruturais (13%) foi observada nas plantas à sombra em relação às plantas ao sol. Não houve diferenças, em base de massa, nos parâmetros de trocas gasosas, com exceção da velocidade máxima de carboxilação tomando-se por base a concentração de CO2 nos sítios de carboxilação, 24% maior nas plantas sombreadas em relação às plantas a pleno sol. Em contraste, em base de área, as plantas de sol exibiram maiores velocidade máxima de carboxilação (32%), taxa fotossintética máxima (45%) e taxa de transporte de elétrons (43%). Aparentemente, a condutância mesofílica tem importância igual ou inferior à da condutância estomática na explicação das baixas taxas fotossintéticas, independentemente da irradiância de crescimento. Sugere-se que a arquitetura hidráulica seja o fator primário mais limitante à fotossíntese no cafeeiro. Os resultados suportam a hipótese de que as plantas sombreadas aproveitariam melhor a energia de sunflecks em relação às plantas de sol, em razão dos maiores estados de ativação e menores perdas de indução fotossintética, além de ausência de fotoinibição nas folhas de sombra. Os resultados ajudam a explicar, em parte, a baixa eficiência fotossintética do uso do N, em decorrência de alto investimento desse elemento em compostos não-fotossintéticos.

Recently, the cold resistance becomes a common topic in scientific articles. If we focus on order Heteroptera, we can find a lot of studies dealing with the cold resistance or with the supercooling point (SCP) and also with the factors that influence them. According to the general rule, the acclimation at low temperatures increases the cold resistance. Therefore, the main goal of this thesis is to find out, whether the acclimation also increases the cold resistance of the water cricket Velia caprai Tamanini, 1947 (Veliidae), with the intention to measure SCP of the water crickets depending on the acclimation temperature and the length of exposure. Due to the high mortality (the 284 individuals remained alive of total 1300) and due to the technical difficulties in measuring of SCP (measured only 36 individuals) it was necessary to modify the original goal of the thesis. The new goal was to test the influence of acclimation (during one month vs. one week) and the influence of different temperatures (0°C, 5°C, 10°C) on SCP of V. caprai. The individuals used for this measurement were collected during the year 2010 and in March 2011. The results of this thesis did not confirm the hypothesis that the acclimation at low temperatures increases the cold resistance. The individuals who were acclimated at a higher temperature have the values of SCP demonstrably lower than the individuals who were acclimated at low temperatures. The individuals who overwinter for the first time have arguably higher cold resistance than the individuals who overwinter for the second time. Probable cause of these results is the fact that the water cricket V. caprai does not start with diapause in the fall but it overwinters in quiescence.

The thesis focuses on regulation of the chlorophyll biosynthetic pathway and its coordination with synthesis of chlorophyll-binding proteins in the cyanobacterium Synechocystis sp. PCC 6803. One of the aims was to analyze correlation between syntheses of photosystems and chlorophyll in Synechocystis cells using radioactive labeling of proteins and chlorophyll by 35S and 14C, respectively. I also investigated the role of enzymes catalyzing protochlorophyllide reduction step in the chlorophyll biosynthesis by analyzing the synthesis and accumulation of photosynthetic proteins in Synechocystis mutants lacking one of the enzymes. Further, roles of Ycf54 and Psb27 proteins in stability and assembly of oxidative cyclase and CP43, respectively, are also described.

Made available in DSpace on 2016-12-23T13:48:26Z (GMT). No. of bitstreams: 1 Manuela Gonoring Soares - texto.pdf: 1466930 bytes, checksum: 1d3ed3b45ce030e2a560ba080600448e (MD5) Previous issue date: 2012-02-28 / A capacidade das plantas em apresentar respostas adaptativas funcionais em relação às condições ambientais é conhecida como plasticidade, podendo ser expressa pelo processo de aclimatação. No ambiente florestal, a luz é um dos fatores principais no estabelecimento e distribuição de espécies vegetais. Neste contexto, espécies mais plásticas apresentam maiores taxas de sobrevivência em relação à variação da disponibilidade luminosa. Os ajustes podem ser fisiológicos, morfológicos e anatômicos e variam de acordo com o nível de exposição à radiação e as características de plasticidade do indivíduo. Dessa forma, o presente estudo teve como objetivo avaliar a plasticidade de plantas jovens de Handranthus chrysotrichus em resposta a diferentes intensidades luminosas. Para tanto, as plantas foram submetidas a três tratamentos: pleno sol (100% de radiação), sombreamento moderado (50% de radiação solar) e sombreamento severo (5% de radiação solar). A plasticidade foi avaliada por meio da análise de modificações de características aos níveis fisiológicos, morfológicos e anatômicos. Foram realizadas análises de crescimento, teor de pigmentos fotossintetizantes, teor de carboidratos solúveis foliares, atividade de enzimas antioxidantes (catalase e peroxidase do ascorbato), anatomia foliar (espessura da cutícula, da epiderme, parênquima paliçádico, mesofilo paravenal, parênquima esponjoso e densidade estomática) e caulinar (espessura da periderme, floema secundário, faixa cambial, xilema secundário e diâmetro, comprimento e densidade dos vasos), testes histoquímicos e índice de plasticidade (IP), após 90 e 200 dias de tratamento. Para as folhas, foram realizadas avaliações em folhas pré-existentes à submissão aos tratamentos e em folhas novas emitidas. As plantas apresentaram respostas comumente encontradas em espécies adaptadas ao sol e à sombra. O crescimento foi estimulado em resposta à alta irradiância, pelo maior acúmulo de massa seca e carboidratos solúveis foliares. O teor de pigmentos fotossintetizantes foi superior nas plantas sob sombreamento severo. A atividade da enzima catalase foi inferior nas plantas submetidas ao pleno sol e a enzima peroxidase do ascorbato não apresentou variação entre os tratamentos ao final do experimento. Em relação à anatomia foliar, houve variações na espessura da cutícula, dos tecidos foliares e na densidade estomática. O caule apresentou variações quanto à espessura dos tecidos avaliados, diâmetro e densidade dos vasos. As variáveis anatômicas analisadas mostraram valores superiores nas plantas em pleno sol e sombreamento moderado. Em relação aos testes histoquímicos, foram encontradas diferenças na deposição de grãos de amido em tecidos caulinares, maior em pleno sol. A análise do IP demonstrou que os ajustes após 90 dias de tratamento foram predominantemente fisiológicos, sendo o teor de pigmentos fotossintetizantes e a massa seca total, as características mais plásticas. Entretanto, ao final de 200 dias de tratamento, os ajustes foram predominantemente morfológicos (massa foliar específica, área foliar específica, razão de área foliar, bem como a produção de massa seca total), anatômicos foliares (espessura do parênquima esponjoso, densidade estomática) e anatômicos caulinares (espessura da faixa cambial). Os resultados obtidos indicam que plantas jovens de H. chrysotrichus apresentam grande plasticidade frente à variação da disponibilidade de luz, o que torna essa espécie recomendada para projetos de reflorestamento e recuperação de áreas degradadas / The ability of plants to show functional adaptive responses in relation to environmental conditions is known as plasticity and can be expressed by the acclimation process. In the forest environment, light is a major factor in the establishment and distribution of plant species. In this context, more plastic species have higher survival rates in relation to the variation of light availability. Adjustments can be physiological, morphological and anatomical and vary with the level of radiation exposure and the characteristics of plasticity of the individual. Thus, this study aimed to evaluate the plasticity of young plants of Handranthus chrysotrichus in response to different light intensities. For this purpose, plants were subjected to three treatments: full sun (100% of solar radiation), moderate shade (50% of solar radiation) and severe shading (5% of solar radiation). The plasticity was evaluated by analyzing changes in physiological characteristics levels, morphological and anatomical. Analyses of growth, photosynthetic pigments content, leaf soluble carbohydrates, antioxidant enzymes (catalase and ascorbate peroxidase), leaf anatomy (thick cuticle, epidermis, palisade parenchyma, paravenal mesophyll, spongy mesophyll and stomatal density) and stem anatomy (thickness of the periderm, secondary phloem, vascular cambium, secondary xylem, diameter, length and density of vessels), histochemical tests and plasticity index (PI) after 90 and 200 days of treatment. For leaves, were evaluated leaves pre-existing to the treatments and new leaves that emerged. Plants show responses commonly found in species adapted to sun and shade. Growth was stimulated in response to high irradiance by the greater accumulation of dry weight and leaf soluble carbohydrates. The content of photosynthetic pigments was higher in plants under severe shading. The catalase activity was lower in plants grown under full sun and the enzyme ascorbate peroxidase did not vary between treatments at the end of the experiment. In relation to leaf anatomy, there were variations in the thickness of the cuticle, of measured leaves tissues and stomatal density. The stem showed variation in the measured tissue thickness, diameter and density of vessels. The anatomic variables analyzed showed higher values in plants in full sun and moderate shade. Regarding the histochemical tests, differences were found in the deposition of starch grains in stem tissues, most in full sun. The analysis of IP demonstrated that the adjustments after 90 days of treatment were predominantly physiological. The content of photosynthetic pigments and the total dry mass were the most plastic characteristics. However, after 200 days of treatment, the settings were predominantly morphological (specific leaf mass, specific leaf area, leaf area ratio, as well as the production of total dry mass), leaf anatomical (thickness of the spongy parenchyma, stomatal density) and anatomical stem (thickness range of vascular cambia). The results indicate that young plants of H. chrysotrichus exhibit great plasticity to the variation of light availability, which makes this recommended species for reforestation and reclamation

Made available in DSpace on 2015-03-26T13:36:40Z (GMT). No. of bitstreams: 1 texto completo.pdf: 265899 bytes, checksum: 81ab8de5806f355ffcac5dc064de5611 (MD5) Previous issue date: 2009-10-30 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / The coffee is indigenous to African tropical forests, where it is found as an understory species growing under shade. In Brazil, however, the coffee plantations have been conducted almost exclusively in full sun. Coffee in full sunlight produce, in most cases, more than shaded plantations, although at the expense of a high investment in photoprotective mechanisms. It is hypothesized that the cultivation of coffee under shade would reduce the negative effects of water deficit (WD). In this study, the photosynthetic performance, the water relations and the antioxidant metabolism were analyzed in plants of Coffea arabica L. cv. ' Catuaí Vermelho'. The plants were grown in pots under three levels of irradiance and three levels of water availability. Overall, there was no statistical significance of the interaction between water and light treatments, but instead an independent and orthogonal response was found. Plants at 35% shading showed higher average rate of net carbon assimilation (A) under moderate WD in the two measurement times (08:00 and 12:00 h); under severe WD A was similar regardless of the light environments. The stomatal conductance (gs) was always higher in control plants than in droughted plants, regardless of the light regime. The total plant transpiration (E) differed significantly among the light treatments and water regimes; higher E rates were found in well-irrigated plants grown in the sun. The total leaf area was similar between plants in shaded environments and higher than in plants in full sun. The photochemical efficiency (Fv/Fm) of photosystem II (PSII) and the capture efficiency of excitation energy by open reaction centers of PSII (Fv'/Fm'), the quantum efficiency of electron transport by PSII (ΦPSII) and the photochemical quenching (qP) all did not respond to the water supply, regardless of the light environments except under severe WD condition in which the use of energy in photochemistry was limited. The coefficient of non-photochemical quenching (NPQ) did not vary in response to moderate WD; however, under severe WD, reductions in NPQ were found. Plants under deep shade (70%) generally showed higher concentrations of total chlorophyll (Chl) and Chl a/b ratio compared with plants from the other light environments, as found at predawn. Total carotenoids (Car) and Chl/Car ratio did not differ significantly at the predawn. The Chl a/b and Chl/Car ratios differed significantly in response to the light environments with the plants full sunlight grown showing the lowest ratios and plants from deep shade the largest ones, but only at midday. Plants in full sun and under 35% shading had antheraxanthin and zeaxanthin concentrations similar to each other, but superior to those of the deepest shaded plants, indicating a greater need for photoprotection. In addition, those plants also showed a higher VAZ pool (sum of the concentrations of violaxanthin, anteraxanthin and zeaxanthin) and higher values of DEPS (depoxidation state of the xanthophylls cycle). Cellular damages, evaluated via electrolyte leakage and production of malondialdehyde, were significantly more severe in plants grown under water deficit than in their control counterparts, regardless of the light environment. From the above, it is believed that the use of 35% shading would be an interesting option to improve environmental conditions without negatively impacting the agronomic performance of shaded coffee plants compared with those grown in full sun. / O cafeeiro é originário das florestas tropicais da África, onde é encontrado como vegetação de sub-bosque, desenvolvendo-se sob sombra. No Brasil, no entanto, os cafezais vêm sendo conduzidos quase exclusivamente a pleno sol. Cafezais a pleno sol produzem, na maioria dos casos, mais que os plantios à sombra, o que deve envolver altos investimentos em mecanismos fotoprotetores. Hipotetiza-se, pois, que o cultivo de cafezais sombreado reduziria os efeitos negativos do déficit hídrico (DH). Neste estudo, pretendeuse analisar o desempenho fotossintético, as relações hídricas e o metabolismo antioxidativo em plantas de Coffea arabica L. cv. Catuaí Vermelho cultivadas em vasos, utilizando-se de três níveis de irradiância e três níveis de disponibilidade hídrica. De modo geral, não foi observada significância estatística da interação entre os tratamentos hídricos e lumínicos, mas uma resposta independente e ortogonal. As plantas do ambiente com sombreamento de 35% apresentaram maiores valores médios da taxa de assimilação líquida de carbono sob DH moderado, nos dois horários de medição (08:00 e 12:00h) e, sob DH severo, não se obserbou diferença significativa na resposta das plantas entre os ambientes lumínicos. A condutância estomática foi sempre maior nas plantas-controle que nas plantas sob DH, independentemente do regime lumínico. A transpiração total das plantas diferiu estatisticamente entre os tratamentos lumínicos e entre os regimes hídricos, apresentando maiores taxas nas plantas dos ambientes com maiores níveis de radiação solar e naquelas mantidas irrigadas. A área foliar total foi similar entre as plantas dos ambientes sombreados e maior em comparação com as plantas a pleno sol. A eficiência fotoquímica máxima do fotossistema II (FSII), assim como a eficiência de captura da energia de excitação pelos centros de reação abertos do FSII, a eficiência quântica do transporte de elétrons pelo FSII e o coeficiente de extinção fotoquímico não responderam aos regimes hídricos, independentemente dos ambientes lumínicos, exceto sob DH severo, condição na qual o uso da energia na fotoquímica foi limitado. O coeficiente de extinção não-fotoquímico (NPQ) não variou em resposta ao DH moderado, porém, sob DH severo, observaram-se reduções em NPQ. As plantas sob sombreamento mais intenso (70%), de modo geral, apresentaram maiores valores de concentrações de clorofilas (Cl) totais e da razão Cl a/b em comparação com as de outros ambientes de luz, na antemanhã. Os carotenóides (Car) totais e a relação Cl/Car não diferiram significativamente na antemanhã. Ao meio-dia, somente os valores médios das razões Cl a/b e Cl/Car diferiram significativamente em relação aos ambientes lumínicos, com as plantas a pleno sol apresentando os menores valores e aquelas do ambiente mais sombreado os maiores. As plantas a pleno sol e sob sombreamento de 35% apresentaram concentrações semelhantes entre si e maiores de anteraxantina e de zeaxantina que as plantas sob 70% de sombreamento, indicando maior necessidade de fotoproteção. Em adição, também apresentaram maior concentração de VAZ (soma das concentrações de violaxantina, anteraxantina e zeaxantina) e maior grau de desepoxidação dos carotenóides do ciclo das xantofilas. Os danos celulares, avaliados via extravasamento de eletrólitos e produção de aldeído malônico, foram significativamente mais intensos nas plantas submetidas ao déficit hídrico do que nos respectivos controles irrigados, independentemente dos ambientes lumínicos. A partir dos resultados encontrados, acredita-se que o uso do sombreamento de 35% seria interessante por melhorar as condições ambientais, pouco afetando o desempenho agronômico dessas plantas em comparação com as cultivadas a pleno sol.

Orientador: Gustavo Maia Souza / Banca: Rafael Vasconcelos Ribeiro / Banca: Carlos Henrique Britto de Assis Prado / Banca: Gustavo Habermann / Banca: José Pires de Lemos Filho / Resumo: As restrições impostas pelo ambiente obrigam as plantas a transitarem entre estados fisiologicamente distintos, podendo tal transição ser representada pelo processo de aclimatação. O aparato fotossintético apresenta alta sensibilidade ao ambiente, mas possui alta capacidade de aclimatação, a qual é necessária dada a sua função essencial no metabolismo vegetal e o seu elevado nível de integração com outras vias metabólicas. A investigação do papel da aclimatação fotossintética na resposta a diversas condições ambientais, em diferentes espécies arbóreas, foi o principal tema de estudo da presente tese. Foram realizados experimentos com espécies arbóreas nativas e cultivadas sob diferentes níveis de controle ambiental, ou seja, no campo, em casa de vegetação e em câmaras de crescimento. Os experimentos com espécies arbóreas nativas envolveram a avaliação da capacidade de aclimatação das espécies de diferentes grupos sucessionais, as quais supostamente apresentam demandas luminosas distintas e diferem em sua habilidade de ajuste e acoplamento ao ambiente. O experimento com a espécie cultivada foi realizado com Eucalyptus globulus, e avaliou o efeito da deficiência hídrica em plantas sob diferentes regimes térmicos. A conjunção dos resultados obtidos nos quatro experimentos realizados permitiu verificar que a aclimatação do aparato fotossintético foi influenciada pelo ambiente de crescimento das plantas e pela estratégia ecológica das espécies, mais conservativa ou mais flexível. Além disso, foi verificado que a estratégia ecológica das espécies não está, necessariamente, relacionada ao seu grupo sucessional, conforme freqüentemente descrito na literatura. Os diversos ajustes no aparato fotossintético, descritos no presente trabalho em diferentes espécies e condições ambientais, demonstraram... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The constraints imposed by the environment compel plants to transit between distinct physiological states, represented by the acclimation process. The photosynthetic apparatus is highly sensitive to the environment, however it presents a high acclimation capacity which is necessary given its essential role in plant metabolism and high level of integration with other pathways. The investigation of the role of photosynthetic acclimation in response of different tree species to diverse environmental conditions was the main subject of the present study. Experiments with tropical tree species and cultivated species were performed under different levels of control of environmental conditions, i.e. in the field, in the greenhouse, and in growth chambers. The experiments with tropical tree species involved the evaluation of the acclimation capacity of species belonging to different ecological groups, supposedly presenting distinct light demands and ability to adjust and couple to the environment. The experiment with cultivated species was carried out with Eucalyptus globulus and photosynthetic acclimation was evaluated under water deficit, in plants under different thermal regimes. The conjunction of the results obtained in the four experiments performed suggests that the acclimation of the photosynthetic apparatus was influenced by the growth environment jointly with the ecological strategy of the species, more conservative or more flexible. Moreover, it was verified that the ecological strategy of the species is not necessarily related with its ecological group as often stated in the literature. The diverse changes in the photosynthetic apparatus described in the present study in different species and environmental conditions, demonstrated the importance and the contribution of the photosynthetic acclimation in the physiological adjustment of a plant to its current environmental condition... (Complete abstract click electronic access below) / Doutor