The research in this thesis concentrates on investigation of the ecology of Arundinaria species for restoration purposes. Arundinaria species are key components in the canebrake ecosystem that was once prominent in the southeastern United States. Arundinaria still occurs as an understory component of bottomland hardwood forests, but with intense agricultural development and urbanization over the past 200 years, canebrakes are now a critically endangered ecosystem with greater than 98% loss. Specifically the thesis addresses the establishment of Arundinaria with other plant species and site preparation techniques. This study indicated that A. gigantea planted into plots dominated by non-native plants benefited significantly more from site preparation (soil tillage, herbicide application) than cane planted into native-species-dominated assemblages. The last portion of the research examined effects of inundation on A. gigantea and A. tecta. Arundinaria tecta appeared to be more flood tolerant than A. gigantea, reflecting habitats in which these species are known to occur.

No description available.

Doctor of Philosophy / Department of Agronomy / P.V. Vara Prasad / The pathway for the movement of water through plants, from the soil matrix to the atmosphere, constitutes the hydraulic architecture of a plant. The linkage between the hydraulic architecture of woody plants and drought tolerance has received considerable attention, but much less work has been done on grasses. I investigated the linkage between the hydraulic architecture of grasses to physiological patterns of water use across a range of species and conditions. The rate of stomatal conductance (g[subscript]s) and photosynthesis (A) increased acropetally along the leaves of 5 grass species, which is a unique feature of this growth form. The internal structure of leaves also changed acropetally in order to minimize the pressure gradient across the mesophyll that would otherwise occur as a result of increasing g[subscript]s. The resistance to water movement through the mesophyll represented 80-90% of leaf resistance in six genotypes of Sorghum bicolor L. (Moench). This resistance was most important in controlling g[subscript]s and A when water was readily available, but as soil-moisture decreased it was the efficient transport of water through the xylem that was most important in maintaining plant function. I also investigated the relationship between hydraulic architecture and stomatal responses of grasses to increasing Vapor Pressure Deficit (D). Grasses with a larger proportion of their hydraulic resistance within the xylem were less sensitive to increasing D and plants with high root conductance maintained higher rates of gas exchange D increased. Finally, I investigated the tolerance of grasses to extreme drought events to test if there was a trade-off between drought tolerance and growth in grasses. Plants with drought tolerant leaf traits typically sacrificed the ability to move water efficiently through their leaves. Having drought tolerant leaves did not limit the plants ability to have high rates of gas exchange, and, in fact, the most drought tolerant plants had the high rates of g[subscript]s when expressed on a mass basis. Leaf-level drought tolerance did contribute to species’ occurrence, as the drought intolerant species I studied are not commonly found in low precipitation systems. The results presented here highlight the importance of studying the hydraulic architecture of plants to provide a better understanding of what controls plant function across a range of environmental conditions.

Realizaram-se campanhas em árvores de cinco anos de idade de Pinus caribaea var. hondurensis e Pinus taeda em parcelas controle (sem fertilização e sem irrigação) e parcelas fertilizadas e irrigadas, durante o verão e o inverno de 2012 visando caracterizar as seguintes variáveis fisiológicas: i) Capacidade máxima fotossintética (Amax); ii) Fotossíntese ao longo do dia (A); iii) Variação da condutância estomática (gs) em relação ao aumento do déficit de pressão de vapor (DPV); e iv) Taxas máximas de carboxilização (Vcmax) e de transporte de elétrons (Jmax) via curvas A/Ci. O estudo foi realizado no projeto Produtividade Potencial do Pinus no Brasil, localizado na Estação Experimental da ESALQ/USP em Itatinga-SP.Foram escolhidas três árvores médias por parcela para as avaliações fisiológicas, realizadas com o LiCor 6400XT. A mensuração da Amax foi realizada no terço médio da copa, em dois galhos por árvore e em duas posições por galho, sendo realizada das 8 às 10 horas, e o comportamento da A, gs com o aumento do DPV, ocorreram de hora em hora, das 11 às 15 horas. Ao final, as acículas foram coletadas para a determinação da área foliar específica (AFE) e do nitrogênio foliar. As curvas A/Ci foram realizadas nas três árvores, um galho por árvore e duas posições por galho, entre 8 e 12 horas. Aos cinco anos o Pinus caribaea var. hondurensis apresenta o dobro do volume de madeira do que o Pinus taeda. As duas avaliações fisiológicas mostraram valores similares entre tratamentos, para cada espécie. Os valores de Amax foram maiores durante o verão e o Pinus caribaea var. hondurensis mostrou grande sensibilidade, comparativamente ao Pinus taeda. Ao analisar os dados de A e gs ao longo do dia, observa-se também maiores variações do Pinus caribaea var. honduresis. Os valores médios de Amax para o verão e o inverno foram 8,2 e 4,8 ?mol m-2 s-1 e 6,8 e 6,3 ?mol m-2 s-1 para o Pinus caribaea var. hondurensis e o Pinus taeda, respectivamente. Ocorreu redução dos valores de A e gs com o aumento do DPV, para ambas as campanhas em relação ao Pinus caribaea var. hondurensis e somente no inverno para o Pinus taeda. As duas espécies apresentaram relação positiva entre fotossíntese e transpiração, sendo que o Pinus caribaea var. hondurensis apresenta maior eficiência no uso da água. As médias da AFE e nitrogênio foliar foram de 9,6 m²kg-1, 10,1g Kg-1 e 10,0 m²kg-1, 13,4g Kg-1, para o Pinus caribaea var. hondurensis e Pinus taeda, respectivamente. Em relação aos parâmetros fotossintéticos o Pinus taeda se destacou em ambas as campanhas, com valores médios de Vcmax e Jmax maiores que o Pinus caribaea var. hondurensis, relacionado à maiores concentrações de nitrogênio foliar. Não houve relação entre o crescimento em biomassa das árvores e as medições da fotossíntese a nível foliar, indicando que outros processos a nível de copa, uso e alocação de fotossintetizados devem ser investigados para explicar a diferença de crescimento. / The campaigns were conducted in trees with five years old of Pinus caribaea var. hondurensis and Pinus taeda in control plots (no fertilization and no irrigation) and fertilized and irrigated plots during summer and winter of 2012 to characterize the physiological variables: i) maximum photosynthetic capacity (Amax), ii) Photosynthesis throughout the day (A); iii) Changes in stomatal conductance (gs) in relation to the increase in vapor pressure deficit (VPD), and iv) Maximum rates of carboxilization (Vcmax) and maximum rates of electron transport (Jmax) based on A/Ci curves. The study was conducted in the project Potential Productivity of Pinus in Brazil, located at the Experimental Station of ESALQ/USP in Itatinga-SP. Three average trees per plot were chosen for physiological evaluations, performed with the LiCor 6400XT. The Amax measurement was performed in the middle third of the crown, in two branches per tree and two positions per branch, taken from 8 to 10am. To get the response of A and gs with increasing VPD, the measurements continued every hour, from 11 am to 3 pm. At the end of the measurements, the needles were collected for determination of specific leaf area (SLA) and leaf nitrogen (N). The A/Ci curves were performed in three trees, one branch per tree and two positions per branch were taken from 8 am to 12 pm. At five years, the Pinus caribaea var. hondurensis showed two-fold the wood volume of Pinus taeda. Both physiological measurements showed similar results between treatments for each species. Amax values were higher during summer, and Pinus caribaea var. hondurensis shower greater sensitivity compared to Pinus taeda. A and gs throughout the day showed higher variation in Pinus caribaea var. hondurensis. The average values of Amax for summer and winter were 8.2, 4.8 ?mol m-2 s-1 and 6.75, 6.3 ?mol m-2 s-1 for Pinus caribaea var. hondurensis and Pinus taeda, respectively. There was a reduction of A and gs with the increasing of DPV, for both campaigns for the Pinus caribaea var. hondurensis and only in winter campaign for Pinus taeda. Thus, the two species have different behaviors in response to climatic changes. The two species showed a positive relationship between photosynthesis and transpiration, with Pinus caribaea var. hondurensis showing greater water use efficiency. The average SLA and needle nitrogen were 9.6 m² kg-1, 10.1g kg-1 and 10 m² kg-1, 13.4g kg-1 for Pinus caribaea var. hondurensis and Pinus taeda, respectively. Photosynthetic parameters in Pinus taeda was higher in both campaigns, with average values of Vcmax and Jmax greater than in Pinus caribaea var. hondurensis, related to higher concentration of needle nitrogen. There was no relationship between tree biomass growth and leaf-level measurements of photosynthesis, indicating that other processes at crown level, use and allocation of photosynthates should be investigated to explain the difference in growth.

Abiotic and biotic stresses affect tree growth and play a major role in determining the geographic distribution of species. The objective of this study is to elucidate the following questions: (1) are GABA aminoacid and stomatal control good indicators of tolerance to water stress in Eucalyptus clones? In addition, what are the anatomical differences between drought-tolerant and drought-sensitive clones of Eucalyptus? (2) Are there differences of xylem vulnerability to cavitation in Pinus flexilis families susceptible and resistant to white pine blister rust (WPBR) and with different origins (high and low altitudes)? Two studies were carried out to elucidate the issues above. On chapters 1, eight Eucalyptus clones from different geographical and climatological conditions, three drought-sensitive (CNB, FIB and JAR), three drought-tolerant (GG, SUZ and VM), and two plastics (VER and COP), were studied in normal water supply (control treatment) and in water stress conditions (stress treatment). The first chapter concluded that GABA is an aminoacid very sensitive to water stress, but there was no relation between GABA concentration and tolerance to water stress of the clones. In addition, all clones decreased stomatal conductance with increasing vapor pressure deficit, and plastics and drought-tolerant clones (except GG) presented lower stomatal sensitivity to vapor pressure deficit under stress conditions than drought-sensitive clones. Besides, all clones showed differences on the anatomical parameters between, and only COP (plastic) and SUZ (drought-tolerant) showed homogeneous mesophyll and amphi-hipostomatic leaves. All clones increased the number of stomata and reduced leaf thickness of the leaves formed after water stress period. On the chapter 2, we studied 12 families of Pinus flexilis originating from high and lower altitudes, in which six families previously shown to contain the dominant C4 allele (resistant to WPBR) and six families without C4 allele (susceptible to WPBR). This study showed that the mean cavitation pressure (MCP) of Pinus flexilis varying between 3.63 a -4.84 Mpa, although there was a significant difference in vulnerability to cavitation comparing all families, this variable was not related to WPBR and origin region. These studies highlight that the physiological responses of plants under water stress conditions are important tools that can be used to complement the strategies of genotype selection in forest breeding programs. / Estresses abióticos e bióticos podem afetar o crescimento das árvores e desempenham um papel importante na determinação da distribuição geográfica das espécies. O objetivo deste estudo, foi elucidar as seguintes questões: (1) o aminoácido GABA e o controle estomático são bons indicadores da tolerância ao estresse hídrico em clones de Eucalyptus? E quais são as diferenças anatômicas entre clones de Eucalyptus tolerantes e sensíveis ao estresse hídrico? (2) existem diferenças de vulnerabilidade a cavitação do xilema entre famílias de Pinus flexilis suscetíveis e resistentes à ferrugem do pinho branco (WPBR) e com diferentes procedências (elevada e baixa altitudes)? Dois estudos foram desenvolvidos para elucidar as questões acima descritas. No capítulo 1, oito clones de Eucalyptus de diferentes procedências e condições climáticas, sendo três clones sensíveis ao estresse hídrico (CNB, FIB e JAR), três clones tolerantes ao estresse hídrico (GG, SUZ e VM) e dois clones plásticos (VER e COP), foram estudados sob duas condições distintas: sob adequado suprimento de água (tratamento controle) e sob condições de estresse hídrico (tratamento estresse). Do primeiro capítulo concluiu-se que o GABA é um aminoácido que possui alta sensibilidade ao estresse hídrico, no entanto, não houve relação entre a concentração de GABA e os níveis de tolerância ao estresse hídrico dos clones. Além disso, todos os clones reduziram a condutância estomática em relação ao aumento do déficit de pressão de vapor (DPV), sendo que, sob condições de estresse hídrico, os clones plásticos e tolerantes à seca (exceto o clone GG) apresentaram menor sensibilidade estomática ao DPV do que os clones sensíveis ao estresse hídrico. Além disso, todos os clones apresentaram diferenças anatômicas, sendo que, diferentemente dos demais, os clones COP (plástico) e SUZ (tolerante) apresentaram mesofilo homogêneo e folhas anfi-hipoestomáticas. Todos os clones aumentaram a quantidade de estômatos e reduziram a espessura foliar das folhas formadas após períodos de estresse hídrico. No segundo capítulo foram avaliadas 12 famílias de Pinus flexilis procedentes de regiões de baixa e alta altitudes, sendo seis famílias contendo um alelo dominante C4 (resistente à WPBR) e seis famílias sem o alelo C4 (suscetíveis à WPBR). Este estudo apresentou uma variação da pressão média da cavitação (MCP) para Pinus flexilis de -3,63 a -4,84 Mpa, e embora tenha havido uma diferença significativa da susceptibilidade a cavitação entre todas as famílias estudadas, esta variável não relacionou-se com a susceptibilidade a doença WPBR e com a região de procedência das famílias. Estes estudos comprovam que a avaliação das respostas fisiológicas das plantas sob condições de estresse hídrico são importantes ferramentas que podem ser utilizadas para complementar as estratégias da seleção de genótipos em programas de melhoramento florestal.

L’agrivoltaïque, association sur une même surface d’une production agricole et d’une production d’énergie d’origine photovoltaïque, apparait aujourd’hui comme une solution innovante pour atténuer les effets du changement climatique, notamment sur le secteur agricole. Déjà imaginé en 1982, les premières expérimentations débutées à Montpellier (France) en 2010 ont montré la pertinence de cette association à travers un maintien des rendements sous certaines conditions, une meilleure efficience d’utilisation du sol ainsi qu’une diminution de la consommation en eau des cultures sous ombrage. Suite à ces travaux pionniers réalisés sous des panneaux photovoltaïques à inclinaison fixe, l’utilisation de panneaux dynamiques à inclinaison variable est apparue nécessaire pour réduire l’hétérogénéité du rayonnement disponible pour la culture mais aussi, adapter la stratégie d’ombrage aux besoins radiatifs de la culture au cours de son développement.La présente thèse avait pour objectif de caractériser et de modéliser l’impact de la présence de panneaux solaires sur le bilan hydrique d’une culture conduite sous dispositif agrivoltaïque dynamique en vue d’optimiser la stratégie d’irrigation et le pilotage de l’inclinaison des panneaux. Les expérimentations menées sur une culture de laitues ont mis en évidence l’intérêt de panneaux dynamiques afin de réduire les hétérogénéités radiatives. Le développement d’un modèle de redistribution des pluies par les panneaux photovoltaïques a permis la mise en œuvre d’une stratégie de pilotage de l’inclinaison en temps réel a permis d’homogénéiser les cumuls observés au sol. L’adaptation d’un modèle de bilan hydrique et de développement de culture par l’ajout d’un module décrivant la dynamique stomatique sous ombrage fluctuant a permis de décrire la consommation en eau de la culture et son développement sous différentes stratégies de pilotage de l’ombrage. Enfin, différentes stratégies de pilotage de l’inclinaison des panneaux photovoltaïque ont pu être simulées et évaluées à l’aide d’un indicateur globale intégrant l’efficience d’utilisation du sol, la productivité de l’eau, le décalage de maturité et les sources d’hétérogénéités pouvant affecter la production de laitues. / Agrivoltaism, defined as the association on the same land of agricultural and photovoltaic energy production, appears as an innovating concept to dampen some of the effects of climate change, in the agricultural sector. Although the concept was already imagined in 1982, the first experimentations started in 2010 at Montpellier (France) and showed the relevance of this combination by the maintenance of crop yield under certain conditions, the increase of land use efficiency and a reduction of water consumption for the tested crops. Following this pioneering work done under fixed (but not horizontal) photovoltaic panels, the use of "dynamic" panels, i.e. panels with a variable tilting angle, appears necessary to reduce the spatial heterogeneity of the transmitted radiation but also to adapt the shading strategy to the radiation amount required for crop growth.This thesis aims to characterize and to model the impact of the photovoltaic panels on the water budget of the cultivated plot and to progress towards the optimization of irrigation strategies in such systems controlled by the variations in time of the tilting angle of the panels. Experimentations conduced on lettuces showed the benefits of "dynamic" photovoltaic panels to reduce the radiative heterogeneity. Accounting for rain redistribution by the solar panels permits the implementation of a real time strategy to reduce rainfall heterogeneity on the ground surface. The derivation of a water budget and crop development model which describes the dynamics of stomatal conductance under fluctuating shading allows a better simulation of water consumption and crop development for different shading strategies. Finally, various strategies for the piloting of the solar panels could be tested and evaluated by a new, global index combining land use efficiency, water productivity, maturity delays and heterogeneities (in rain and radiation) which can impact production.

Air pollutant exposure poses a health risk to humans and impacts negatively on agriculture. High levels of air pollution resulted in extensive crop damage and yield reduction in Europe and USA. The Highveld region in South Africa, a very important area for maize and soya production, has already been declared an air pollution hot spot, with SO2 being the most concerning air pollutant. Most of the SO2 over the Highveld originates from the burning of coal for power generation. Developing countries, such as South Africa, are highly dependent on agriculture for food security and high levels of air pollution pose serious risks to the agricultural industry. Currently very little information is available on the effects of air pollution on crop production in South Africa. This study aimed to establish exposure-response relationship for SO2 on soybean and the quantification thereof on the morphological, physiological and biochemical characteristics. Two soybean cultivars were used, namely: LS 6164 and PAN 1666. The plants were fumigated for 7 hours, 7 days a week with 0 (carbon filtered control; CF), 25, 75 and 150 ppb SO2. The effect of SO2 was investigated on the growth, photosynthetic capabilities, photosynthetic gas exchange, peroxidase activity and lipoxygenase activity of the cultivars. Foliar injuries and interveinal chlorosis were visible with increasing levels of SO2 as well as a decrease in biomass accumulation, especially in root biomass; a more prominent feature of LS 6164. The number of nodules of both cultivars decreased insignificantly as the levels of SO2 increased. The number of pods per plant and the average weight of 30 seeds indicated a downward trend with an increase in SO2 concentration. The chlorophyll content of PAN 1666 was lower compared to LS 6164. PAN 1666 had the largest reduction in stomatal conductance at 150 ppb SO2 fumigation. The photosynthetic vitality index indicated that LS 6164 was more sensitive to SO2 inhibition from 25 ppb SO2 and higher, whereas PAN 1666 mostly became sensitive to SO2 from 75 ppb SO2. A decrease in the ability to absorb light energy, the trapping of excitation energy to transfer electrons beyond QA-, and the reduction of end electron acceptors all contributed to the decline in the vitality index. Sulphur content increased significantly in the 75 ppb and 150 ppb treatments of both cultivars. Induced peroxidase and lipoxygenase activity was seen in both cultivars, especially at higher concentrations of SO2 treatments. PAN 1666 had a higher rate of peroxidase and lipoxygenase activity compared to LS 6164. The implication for SO2 on crop production in the highly industrial Highveld area was demonstrated to be potentially of great concern. The dose-response relationships plotted for OJIP parameters emphasized that SO2 is an inhibitor of photosynthesis and phytotoxic of nature. Both cultivars experienced limitations from 75 ppb, especially at the 150 ppb SO2 concentration. From these results it appears that PAN 1666 is more adapted to SO2 compared to LS 6164 and levels of 75 ppb SO2 and higher become toxic to these plants. / Thesis (Master of Environmental Sciences)--North-West University, Potchefstroom Campus, 2013

Air pollutant exposure poses a health risk to humans and impacts negatively on agriculture. High levels of air pollution resulted in extensive crop damage and yield reduction in Europe and USA. The Highveld region in South Africa, a very important area for maize and soya production, has already been declared an air pollution hot spot, with SO2 being the most concerning air pollutant. Most of the SO2 over the Highveld originates from the burning of coal for power generation. Developing countries, such as South Africa, are highly dependent on agriculture for food security and high levels of air pollution pose serious risks to the agricultural industry. Currently very little information is available on the effects of air pollution on crop production in South Africa. This study aimed to establish exposure-response relationship for SO2 on soybean and the quantification thereof on the morphological, physiological and biochemical characteristics. Two soybean cultivars were used, namely: LS 6164 and PAN 1666. The plants were fumigated for 7 hours, 7 days a week with 0 (carbon filtered control; CF), 25, 75 and 150 ppb SO2. The effect of SO2 was investigated on the growth, photosynthetic capabilities, photosynthetic gas exchange, peroxidase activity and lipoxygenase activity of the cultivars. Foliar injuries and interveinal chlorosis were visible with increasing levels of SO2 as well as a decrease in biomass accumulation, especially in root biomass; a more prominent feature of LS 6164. The number of nodules of both cultivars decreased insignificantly as the levels of SO2 increased. The number of pods per plant and the average weight of 30 seeds indicated a downward trend with an increase in SO2 concentration. The chlorophyll content of PAN 1666 was lower compared to LS 6164. PAN 1666 had the largest reduction in stomatal conductance at 150 ppb SO2 fumigation. The photosynthetic vitality index indicated that LS 6164 was more sensitive to SO2 inhibition from 25 ppb SO2 and higher, whereas PAN 1666 mostly became sensitive to SO2 from 75 ppb SO2. A decrease in the ability to absorb light energy, the trapping of excitation energy to transfer electrons beyond QA-, and the reduction of end electron acceptors all contributed to the decline in the vitality index. Sulphur content increased significantly in the 75 ppb and 150 ppb treatments of both cultivars. Induced peroxidase and lipoxygenase activity was seen in both cultivars, especially at higher concentrations of SO2 treatments. PAN 1666 had a higher rate of peroxidase and lipoxygenase activity compared to LS 6164. The implication for SO2 on crop production in the highly industrial Highveld area was demonstrated to be potentially of great concern. The dose-response relationships plotted for OJIP parameters emphasized that SO2 is an inhibitor of photosynthesis and phytotoxic of nature. Both cultivars experienced limitations from 75 ppb, especially at the 150 ppb SO2 concentration. From these results it appears that PAN 1666 is more adapted to SO2 compared to LS 6164 and levels of 75 ppb SO2 and higher become toxic to these plants. / Thesis (Master of Environmental Sciences)--North-West University, Potchefstroom Campus, 2013

Made available in DSpace on 2016-08-12T19:15:20Z (GMT). No. of bitstreams: 1 ValmorET_DISSERT.pdf: 1152615 bytes, checksum: db476e005af6cccba35d383e70cb2af7 (MD5) Previous issue date: 2012-03-14 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Tabebuia impetiginosa is a tree species, known as pau d'arco or ipe-roxo. It is found in Caatinga areas, and is of great importance to this biome, its wood is much appreciated, and because it contains in its bark substances that act against cancer. This species has been used in land restoration programs. Species of this biome, such as ipe-roxo, present several morphophysiological changes as a way to adapt to the dry seasons of the year. The study of these changes is of great importance, and it s necessary to understand these mechanisms so that we can manage and conserve these species. Therefore, this study aims to evaluate the ecophysiological behavior of Tabebuia impetiginosa in response to water stress and rehydration. For this purpose an experiment was conducted in a greenhouse at the Universidade Federal Rural do Semi-Arido. The fruits were collected from trees of the same University and sowed in soil from two locations, Mossoro, and Angicos, this one collected in an area in process of desertification. When the seedlings reached nine months in the dry season, the treatments were applied, consisted of a set of two factors. the first one were the two soil types (Mossoró and Angicos) and the second, two water regimes with three replications, with each repetition represented by three plants. The evaluations were performed every three days during the period of suspension of irrigation in seedlings with and without irrigation, and the return of irrigation determined by monitoring the onset of leaf fall in plants subjected to irrigation suspension. After this period the plants were rehydrated, and evaluations done until the photosynthesis rates of the seedlings that were subjected to irrigation suspension equalized to the ones that were not submitted. The variables investigated were photosynthesis (A), stomatal conductance (E), internal CO2 concentration (Ci), transpiration (E), water use efficiency (A/E), carboxylation efficiency (A/Ci) and leaf water potential (Ψw) at predawn and midday.The soil of Mossoro presented greater rates of A and E in some evaluations when exposed to good water conditions when compared to the Angicos soil. This response in this condition was not related to gs. When subjected to stress, the of ipe-roxo seedlings in Angicos soil reduced their leaf Ψw before the seedlings grown in Mossoro soil. When rehydrated, seedlings grown in Angicos soil recovered their leaf Ψw before the plants grown in Mossoro soil. Regardless of the soil, water stress affected A, E, gs, and Ci, with decrease of these variables and rapid recovery after rehydration. In contrast, there was an increase in A/E during water stress, and this occurred earlier in plants grown in Mossoro soil. With water stress there was a the reduction of leaf Ψw, this reduction being found earlier in Angicos soil and in predawn. The Tabebuia impetiginosa presents itself as an investor plant, with an ability to reduce its leaf Ψw in water shortage conditions / Tabebuia impetiginosa é uma espécie arbórea, conhecida como pau-d`arco ou ipê-roxo. Encontrada em áreas da Caatinga, é de grande importância para esse bioma, possuindo madeira muito apreciada, e por conter em sua casca substâncias que agem contra o câncer. Essa espécie vem sendo usada em programas de recuperação de áreas degradadas. Espécies desse bioma, como o Ipê-roxo, apresentam diversas alterações morfofisiológicas como forma de adaptação às épocas secas do ano. O estudo dessas alterações é de grande importância, sendo necessário conhecer esses mecanismos para que se possa manejar e conservar essas espécies. Logo, objetiva-se nesse estudo avaliar o comportamento ecofisiológico de Tabebuia impetiginosa em resposta ao estresse hídrico e a reidratação. Para isso foi realizado um experimento na casa de vegetação da Universidade Federal Rural do Semi-Árido. Os frutos foram coletados em árvores da mesma Universidade e a semeadura realizada em solos de duas localidades, Mossoró, e Angicos, esse último coletado em uma área em processo de desertificação. Quando as mudas atingiram nove meses, na estação seca do ano, foram aplicados os tratamentos, constituídos de um conjunto de dois fatores, sendo o primeiro, dois tipos de solo (Mossoró e Angicos) e o segundo, dois regimes hídricos com três repetições, com cada repetição representada por três plantas. O delineamento experimental foi em blocos casualizados. As avaliações foram realizadas a cada três dias, durante o período de suspensão da irrigação, em mudas com e sem irrigação, sendo a retomada da irrigação determinada pelo monitoramento do início da queda das folhas, nas plantas submetidas à suspensão. Após esse período as mudas foram reidratadas, e as avaliações realizadas até que as taxas de fotossíntese das mudas que foram submetidas à suspensão igualassem às que não foram submetidas. As variáveis avaliadas foram fotossíntese (A), condutância estomática (gs), concentração interna de CO2 (Ci), transpiração, Eficiência de uso da água (A/E), Eficiência de carboxilação (A/Ci) e o potencial hídrico foliar (Ψw) ao pré-amanhecer e ao meio-dia. O solo de Mossoró apresentou maiores taxas de A e E em determinados períodos de avaliação quando submetido a boa condição hídrica em relação ao solo de Angicos. Essa resposta, nessa condição, não esteve relacionada à gs. Quando submetido ao estresse, as mudas de Ipê-roxo no solo de Angicos reduziram seu Ψw foliar antes das mudas cultivada no solo de Mossoró. E quando reidratadas, mudas cultivadas no solo de Angicos recuperaram seu Ψw foliar antes do solo de Mossoró. Independente do solo estudado o estresse hídrico afeta A, E, gs, Ci, com decréscimo dessas variáveis e rápidas recuperações após a reidratação. Diferentemente, a A/E, presenta um aumento com o estresse hídrico, sendo esse verificado antes em mudas cultivadas no solo de Mossoró. Com o estresse hídrico ocorre a redução do Ψw foliar, sendo essa redução encontrada antes no solo de Angicos e no período anterior ao amanhecer. A Tabebuia impetiginosa apresenta-se como uma espécie investidora, apresentando capacidade de reduzir seu Ψw foliar em condições de falta de água

Made available in DSpace on 2016-08-12T19:18:41Z (GMT). No. of bitstreams: 1 ValmorET_DISSERT.pdf: 1152615 bytes, checksum: db476e005af6cccba35d383e70cb2af7 (MD5) Previous issue date: 2012-03-14 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Tabebuia impetiginosa is a tree species, known as pau d'arco or ipe-roxo. It is found in Caatinga areas, and is of great importance to this biome, its wood is much appreciated, and because it contains in its bark substances that act against cancer. This species has been used in land restoration programs. Species of this biome, such as ipe-roxo, present several morphophysiological changes as a way to adapt to the dry seasons of the year. The study of these changes is of great importance, and it s necessary to understand these mechanisms so that we can manage and conserve these species. Therefore, this study aims to evaluate the ecophysiological behavior of Tabebuia impetiginosa in response to water stress and rehydration. For this purpose an experiment was conducted in a greenhouse at the Universidade Federal Rural do Semi-Arido. The fruits were collected from trees of the same University and sowed in soil from two locations, Mossoro, and Angicos, this one collected in an area in process of desertification. When the seedlings reached nine months in the dry season, the treatments were applied, consisted of a set of two factors. the first one were the two soil types (Mossoró and Angicos) and the second, two water regimes with three replications, with each repetition represented by three plants. The evaluations were performed every three days during the period of suspension of irrigation in seedlings with and without irrigation, and the return of irrigation determined by monitoring the onset of leaf fall in plants subjected to irrigation suspension. After this period the plants were rehydrated, and evaluations done until the photosynthesis rates of the seedlings that were subjected to irrigation suspension equalized to the ones that were not submitted. The variables investigated were photosynthesis (A), stomatal conductance (E), internal CO2 concentration (Ci), transpiration (E), water use efficiency (A/E), carboxylation efficiency (A/Ci) and leaf water potential (Ψw) at predawn and midday.The soil of Mossoro presented greater rates of A and E in some evaluations when exposed to good water conditions when compared to the Angicos soil. This response in this condition was not related to gs. When subjected to stress, the of ipe-roxo seedlings in Angicos soil reduced their leaf Ψw before the seedlings grown in Mossoro soil. When rehydrated, seedlings grown in Angicos soil recovered their leaf Ψw before the plants grown in Mossoro soil. Regardless of the soil, water stress affected A, E, gs, and Ci, with decrease of these variables and rapid recovery after rehydration. In contrast, there was an increase in A/E during water stress, and this occurred earlier in plants grown in Mossoro soil. With water stress there was a the reduction of leaf Ψw, this reduction being found earlier in Angicos soil and in predawn. The Tabebuia impetiginosa presents itself as an investor plant, with an ability to reduce its leaf Ψw in water shortage conditions / Tabebuia impetiginosa é uma espécie arbórea, conhecida como pau-d`arco ou ipê-roxo. Encontrada em áreas da Caatinga, é de grande importância para esse bioma, possuindo madeira muito apreciada, e por conter em sua casca substâncias que agem contra o câncer. Essa espécie vem sendo usada em programas de recuperação de áreas degradadas. Espécies desse bioma, como o Ipê-roxo, apresentam diversas alterações morfofisiológicas como forma de adaptação às épocas secas do ano. O estudo dessas alterações é de grande importância, sendo necessário conhecer esses mecanismos para que se possa manejar e conservar essas espécies. Logo, objetiva-se nesse estudo avaliar o comportamento ecofisiológico de Tabebuia impetiginosa em resposta ao estresse hídrico e a reidratação. Para isso foi realizado um experimento na casa de vegetação da Universidade Federal Rural do Semi-Árido. Os frutos foram coletados em árvores da mesma Universidade e a semeadura realizada em solos de duas localidades, Mossoró, e Angicos, esse último coletado em uma área em processo de desertificação. Quando as mudas atingiram nove meses, na estação seca do ano, foram aplicados os tratamentos, constituídos de um conjunto de dois fatores, sendo o primeiro, dois tipos de solo (Mossoró e Angicos) e o segundo, dois regimes hídricos com três repetições, com cada repetição representada por três plantas. O delineamento experimental foi em blocos casualizados. As avaliações foram realizadas a cada três dias, durante o período de suspensão da irrigação, em mudas com e sem irrigação, sendo a retomada da irrigação determinada pelo monitoramento do início da queda das folhas, nas plantas submetidas à suspensão. Após esse período as mudas foram reidratadas, e as avaliações realizadas até que as taxas de fotossíntese das mudas que foram submetidas à suspensão igualassem às que não foram submetidas. As variáveis avaliadas foram fotossíntese (A), condutância estomática (gs), concentração interna de CO2 (Ci), transpiração, Eficiência de uso da água (A/E), Eficiência de carboxilação (A/Ci) e o potencial hídrico foliar (Ψw) ao pré-amanhecer e ao meio-dia. O solo de Mossoró apresentou maiores taxas de A e E em determinados períodos de avaliação quando submetido a boa condição hídrica em relação ao solo de Angicos. Essa resposta, nessa condição, não esteve relacionada à gs. Quando submetido ao estresse, as mudas de Ipê-roxo no solo de Angicos reduziram seu Ψw foliar antes das mudas cultivada no solo de Mossoró. E quando reidratadas, mudas cultivadas no solo de Angicos recuperaram seu Ψw foliar antes do solo de Mossoró. Independente do solo estudado o estresse hídrico afeta A, E, gs, Ci, com decréscimo dessas variáveis e rápidas recuperações após a reidratação. Diferentemente, a A/E, presenta um aumento com o estresse hídrico, sendo esse verificado antes em mudas cultivadas no solo de Mossoró. Com o estresse hídrico ocorre a redução do Ψw foliar, sendo essa redução encontrada antes no solo de Angicos e no período anterior ao amanhecer. A Tabebuia impetiginosa apresenta-se como uma espécie investidora, apresentando capacidade de reduzir seu Ψw foliar em condições de falta de água