Orientador: Gustavo Habermann / Resumo: O alumínio (Al) é o metal mais abundante na crosta terrestre. Em solos ácidos (pH < 5,0) é encontrado principalmente na forma de Al3+, tóxico à maioria das plantas. Nas plantas sensíveis a esse metal, o primeiro e mais conspícuo sintoma de toxicidade é a inibição do crescimento das raízes, onde a maior parte do Al é covalentemente retido. Além disso, o Al também causa sintomas indiretos, reduzindo o crescimento da parte aérea. Tal redução tem sido associada à assimilação de CO2 (A), e evidências sugerem o comprometimento das reações fotoquímicas, além da redução de 30 a 80% da condutância estomática (gs). Além disso, o Al também tem sido associado à redução na hidratação do mesofilo, como ocorre em condições de limitação hídrica. Baseado nestes fatos, testamos a hipótese de que parte dos sintomas de fitotoxicidade ao Al em plantas sensíveis, sobretudo aqueles relacionados ao baixo crescimento e desenvolvimento da parte aérea, bem como menos trocas gasosas, ocorrem em resposta à ativação de mecanismos associados à percepção de deficiência hídrica, principalmente à biossíntese de ácido abscísico (ABA). Utilizamos duas espécies sensíveis ao Al, mas cujos sintomas de toxicidade são induzidos por concentrações significativamente distintas, como Solanum lycopersicum (100 M Al) e Citrus limonia (1480 M Al). As plantas foram cultivadas em solução de nutrientes com e sem Al, em experimentos independentes com duração de 10 e 90 dias, para S. lycopersicum e C. limonia, respectivamente... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Aluminum (Al) is the most abundant metal in the Earth's crust. In acidic soils (pH < 5.0) it is found mostly as Al3+, which is toxic to most plants. In Al-sensitive plants, the first and most conspicuous symptom is the inhibition of the growth of the root system, where most of Al is covalently retained. Aluminum also causes indirect symptoms, such as reduced shoot growth. In Al-sensitive plants, Al-reduced CO2 assimilation rate (A) is observed, and there is evidence suggesting the impairment of photochemical reactions, as well as 30 to 80% reduction in stomatal conductance (gs). In addition, Al has also been associated with a reduction in mesophyll hydration, as occurs under water-limited conditions. Based on these facts, we tested the hypothesis that part of Al symptoms in sensitive plants, especially those related to low shoot growth and development, as well as low gas exchange, occur in response to activation of mechanisms closely associated with the perception of water deficiency, especially as signalled by abscisic acid (ABA) biosynthesis. We used two Al-sensitive species, whose symptoms of toxicity are induced by significantly different concentrations, such as Solanum lycopersicum (100 M Al) and Citrus limonia (1480 M Al). Plants were grown in nutrient solution with and without Al, in independent experiments of 10 and 90 days, for S. lycopersicum and C. limonia, respectively. In the experiments with both species, biometric parameters, root system morphology, biomass, ... (Complete abstract click electronic access below) / Doutor

Methods for rapid, safe and effective detection of unmapped buried ordnance are vital to the protection of humans and environmental quality throughout the world. This study aimed to investigate the use of phytosensing and to understand the physiological response of woody plants to 2,4,6-trinitrotoluene (TNT) contamination. Baccharis halimifolia were potted in soils containing various concentrations of TNT and physiological responses were observed over a 9-week experimental period. Measurements included the collection of remotely sensed data, such as hyperspectral reflectance and chlorophyll fluorescence, and traditional plant-level physiological data. In accordance with the hypothesis, low levels of TNT improved physiological response in plants due to the slight increase in nitrogen, while high levels of TNT induced stress. Key markers in stress responses were identified, specifically with reflectance indices and derivatives, which may separate TNT-contaminated plants from naturally stressed plants and would allow for accurate detection of buried ordnance at the landscape level.

The forest product industry is keenly interested in extending the normal planting season, as well as in the comparative field performance of standard nursery bare-root seedlings and containerized rooted cuttings. The effect of seasonal planting dates on survival, above and belowground biomass allocation, water relations, gas exchange attributes and foliar carbon isotope composition (δ13C) of two stock types of slash pine (Pinus elliottii Engelm.) were examined. Slash pine bare-root seedlings (BRS) and containerized rooted cuttings (CRC) were hand planted in September, November, January, March and April in three consecutive planting seasons (2000-2001, 2001-2002 and 2002-2003) on three sites with silt loam topsoils in southwestern Louisiana. First-year mean survival of CRC across all planting dates and sites was consistently high at 96 to 98%, whereas BRS survival was significantly (P < 0.0001) lower at 59 to 81% and highly variable among study sites and dates through three planting seasons. Generally, there was a negative relationship between soil moisture at the time of planting and first-year survival of BRS planted September through March in 2001-2002 and 2002-2003 planting seasons, whereas the opposite was observed only for BRS planted in April 2002 and 2003. Survival of CRC was affected very little by the variation in soil moisture. Containerized rooted cuttings had higher early above and belowground biomass, and height and diameter than did BRS. However, three years after planting the size differences between stock types disappeared or became negligible. Early size differences among trees planted September through March also decreased after three years, although September trees were tallest. Growth of the April-planted trees was poor compared to trees planted in other months. Late-planted April trees had higher δ13C values, and higher water-use efficiency in the first growing season compared to earlier planted trees. Differences in δ13C values among the planting dates disappeared in the second growing season. Net photosynthesis rates did not differ considerably between stock types or among planting dates in the second and third growing seasons. This study indicates that it is possible to extend the planting season to as early as September and as late as March by using CRC.

The forest product industry is keenly interested in extending the normal planting season, as well as in the comparative field performance of standard nursery bare-root seedlings and containerized rooted cuttings. The effect of seasonal planting dates on survival, above and belowground biomass allocation, water relations, gas exchange attributes and foliar carbon isotope composition (&#948;13C) of two stock types of slash pine (Pinus elliottii Engelm.) were examined. Slash pine bare-root seedlings (BRS) and containerized rooted cuttings (CRC) were hand planted in September, November, January, March and April in three consecutive planting seasons (2000-2001, 2001-2002 and 2002-2003) on three sites with silt loam topsoils in southwestern Louisiana. First-year mean survival of CRC across all planting dates and sites was consistently high at 96 to 98%, whereas BRS survival was significantly (P < 0.0001) lower at 59 to 81% and highly variable among study sites and dates through three planting seasons. Generally, there was a negative relationship between soil moisture at the time of planting and first-year survival of BRS planted September through March in 2001-2002 and 2002-2003 planting seasons, whereas the opposite was observed only for BRS planted in April 2002 and 2003. Survival of CRC was affected very little by the variation in soil moisture. Containerized rooted cuttings had higher early above and belowground biomass, and height and diameter than did BRS. However, three years after planting the size differences between stock types disappeared or became negligible. Early size differences among trees planted September through March also decreased after three years, although September trees were tallest. Growth of the April-planted trees was poor compared to trees planted in other months. Late-planted April trees had higher &#948;13C values, and higher water-use efficiency in the first growing season compared to earlier planted trees. Differences in &#948;13C values among the planting dates disappeared in the second growing season. Net photosynthesis rates did not differ considerably between stock types or among planting dates in the second and third growing seasons. This study indicates that it is possible to extend the planting season to as early as September and as late as March by using CRC.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv. / Härtill 6 uppsatser.

Submitted by (lucia.rodrigues@ufrpe.br) on 2016-08-22T12:48:14Z No. of bitstreams: 1 Adenilda Ribeiro de Moura.pdf: 1066028 bytes, checksum: 3c782cbb4d5d70f96ff97cd2cfa12623 (MD5) / Made available in DSpace on 2016-08-22T12:48:15Z (GMT). No. of bitstreams: 1 Adenilda Ribeiro de Moura.pdf: 1066028 bytes, checksum: 3c782cbb4d5d70f96ff97cd2cfa12623 (MD5) Previous issue date: 2010-02-26 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The objective of the present work was to verify alterations in the growth, the gas exchanges and biochemical composition changes of tame nut plants (Jatropha curcas L.) cultivated in greenhouse under water deficiency. The present research was developed in greenhouse of the Laboratory of Plant Physiology of the Agricultural Federal University of Pernambuco, between December of 2008 to June of 2009, with experimental period of 120 days. The plant were propagated seeds proceeding from the Center of Agricultural Sciences of the Federal University of Alagoas - UFAL, in the Rio Largo city , Alagoas State, situated around ' 57,3' the geographic coordinates 09º 27'' 57,4' S and 35º 49' W. The seeds had been ece of fishes to germinate in trays with capacity for 17 kg of ground. The same ones had been used dumb with 25 days of age had been transferred to vases contend 11kg of ground, classified as Neossolo Regolitico, coming from the Experimental Station of the IPA (Company Pernambucana de Farming Pesquisa), in the city of Caruaru/PE collected in two depths of 0-20 and 20- 40 cm, placing in in layers vases overlapped to simulate the natural conditions of caatinga. The experimental delineation entirely was casualizado with four water levels in the ground: 100%, 80%, 60% and 40% of the pot capacity (CP) with six repetitions. To each fifteen days had been evaluated height of the plant, leaf number, diameter of caule. To the end of the experimental period, the foliar area, the reason of foliar area, the production of dry substance of leves, caule, roots and total had been determined and the allocation of biomass for leves, caule and roots. The leaf water potential, the relative water text was evaluated at three times (60, 90 and 120 days after the differentiation) in two schedules of evaluation 4h (antemanhã) and to the noon. Daily they had been taken measured by the temperature and relative humidity of air in the interior of the house of vegetation for I calculate it of the deficit of water vapor pressure. Also a daily course was made to identify the schedule of bigger estomática opening of the species. At the three times of evaluation they had been also made you analyze biochemists (free amino acids, soluble proteins, soluble carbohydrates and free prolina) and had been evaluated texts of clorofilas, b, carotenóides in same leves used for the foliar hídrico potential. The hídrico deficit affected in the 0 variable of growth in the treatments with 60% and 40% CP in leaf number, diamerter of stem and height of the plant in relation to the plants with 100% CP, being able to be observed significant differences in the total dry substance, allocation of biomass of the root, caule and leves also in the treatments with 60 and 40% of field capacity. In relation the gaseous exchanges presented values significant for the studied 0 variable Tfol x Ur x DPV and and x Rs to the 90 days, in the submitted plants 60% and 40% of the capacity of field in relation to the plant has controlled. Significant differences in the organic solutos for the treatments had been observed most severe, also o CP urring with the leaf water potentil at the three times of evaluation, what it evidences that the species in situation of estres a CP umulates organic solutos and consequently diminishes the leaf water potentil. The Jatropha when submitted the water levels below of 60% CP, it has its compromised development, however the species does not paralyze its growth. / O objetivo do presente trabalho foi analisar alterações nas relações hídricas, teor de solutos orgânicos e crescimento de mudas de pinhão manso (Jatropha curcas L.) sob diferentes níveis de déficit hídrico. A pesquisa foi conduzida em casa de vegetação do Laboratório de Fisiologia Vegetal do Departamento de Biologia da Universidade Federal Rural de Pernambuco – UFRPE, no período de dezembro de 2008 a junho de 2009. As mudas foram provenientes de sementes coletadas no campo experimental, do Centro de Ciências Agrárias da Universidade Federal de Alagoas, no Município de Rio Largo. As sementes foram colocadas para germinar em bandejas contendo areia lavada, e quando as plântulas apresentaram de quatro a seis folhas, foram selecionadas quanto a uniformidade de tamanho e sanidade e transferidas para vasos de polietileno com capacidade para 11kg de solo, classificado como Neossolo Regolítico, procedente da Estação Experimental do IPA (Empresa Pernambucana de Pesquisa Agropecuária), no município de Caruaru/PE, coletado nas profundidades de 0-20 e 20-40 cm, colocados nos vasos em camadas sobrepostas e mantidos em casa de vegetação sem adubação para simular as condições naturais da Caatinga O delineamento experimental adotado foi inteiramente casualizado, correspondendo a quatro níveis de água no solo: 100%, 80%, 60% e 40% da capacidade de pote (CP) com seis repetições. O potencial hídrico foliar e o teor relativo de água foi avaliado em três épocas (60, 90 e 120 dias após a diferenciação) em dois horários de avaliação na antemanhã (4h) e ao meio-dia (12h). Nas três épocas de avaliação também foram feitas análises bioquímicas (aminoácidos livres, proteínas solúveis, carboidratos solúveis e prolina livre) e foram avaliados os teores de clorofilas a, b, carotenóides nas mesmas folhas utilizadas para a determinação do potencial hídrico foliar. A cada sete dias foram avaliados altura da planta, número de folhas, diâmetro do caule. Ao final do período experimental, foram determinadas a área foliar, a razão de área foliar, a produção de matéria seca das folhas, caule, raízes e total e a alocação de biomassa para as folhas, caule e raízes. Com o aumento do estresse foram observadas diferenças significativas nos teor de solutos orgânicos para os tratamentos mais severos, ocorrendo paralelamente queda no potencial hídrico foliar nas três épocas de avaliação, o que evidencia que a espécie em situação de estresse acumula solutos orgânicos e conseqüentemente diminui o potencial hídrico foliar. Os pigmentos fotossintetizantes apresentaram reduções no tratamento mais severo em relação ao controle para os teores de clorofila a/b, total e pela estimativa do Índice do SPAD aos 90 dias de tratamentos hídricos nas plantas com 40% CP. O déficit hídrico afetou nas variáveis de crescimento nos tratamentos com 60 % e 40 % CP no número de folhas, diâmetro do caule e altura da planta em relação às plantas com 100% CP, a J. curcas quando submetida a níveis d’água abaixo de 60% CP, tem seu desenvolvimento comprometido, entretanto a espécies não paralisa seu crescimento. Foram observadas diferenças significativas na matéria seca total, alocação de biomassa da raiz, caule e folhas também nos tratamentos com 60 e 40 % de capacidade de campo.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Water is essential to the survival of plants. Reductions in availability, caused by high evaporative demand and/or supply limitation, can lead to numerous morphophysiological changes in the plant. The Caatinga biome, located in the Brazilian semi-arid region, is characterized by an irregular rainfall regime associated with high temperatures, causing, therefore, situations of water deficiency to the plants that live there. Occurring naturally in the Caatinga, especially associated with the São Francisco River, in floodplain and humid slopes of the Matogrossense pantanal, the pajeuzeiro is a tree that has important importance in the ornamentation, popular medicine, wood supply and restoration of degraded areas. The mechanisms used by the pajeuzeiro to survive in situations of water deficit are still scarce. In view of this, the present work had the objective of investigating physiological and biochemical changes of the pajeuzeiro when submitted to the water deficit, as well as its capacity of recovery after the rehydration. For this, a greenhouse experiment was carried out in a completely randomized design, with four treatments to recover water lost by evapotranspiration (T100 - control, T50 - 50%, T25 - 25% and T0 - without replacement) repetitions each. Leaf water potential (Ψw), relative water content (TRA), foliar protoplasm tolerance, gas exchange (gs, E, A and WUE), as well as chlorophyll fluorescence a were evaluated. For the biochemical analyzes, the content of photosynthetic pigments (Chl a, Chl b, total Chl and carotenoids), soluble proteins, free proline and carbohydrates were analyzed. The Pajeuzeiro was affected by the water deficit, with a significant reduction in its Ψw and TRA, which reached values below 60%. In addition, significant reductions in stomatal conductance (gs), transpiration (E), photosynthetic rate (A), quantum efficiency of PSII (Fv/Fm), area and performance index (PIABS) were observed in treatments under water deficit. As the water deficit intensified, an increase in the percentage of membrane damage was observed, with T0 presenting the highest damage index in relation to the control. The restriction in water availability also significantly affected the concentration of photosynthetic pigments, with reductions for chl a, b and total and increase for carotenoids. In addition, the deficit promoted a significant increase in the concentration of soluble proteins for T0 and T25 and of free proline for the three treatments with water deficiency. For the carbohydrate concentration, there was an increase, but not significant. The pajeuzeiro was strongly affected by the water deficit, but demonstrated a strong recovery capacity of all parameters analyzed after rehydration, which shows a certain degree of tolerance of the species. Therefore, the Triplaris gardneriana species uses stomatal closure, along with leaf senescence and abscision, as the main mechanism to prevent excessive water loss. / A água é substância essencial à sobrevivência dos vegetais. Reduções em sua disponibilidade, causada por elevada demanda evaporativa e/ou por limitação no suprimento, podem acarretar inúmeras alterações morfofisiológicas na planta. O bioma Caatinga, localizado no semiárido brasileiro, caracteriza-se por apresentar um regime irregular de chuvas associado a elevadas temperaturas, ocasionando, portanto, situações de deficiência hídrica aos vegetais que lá habitam. Ocorrendo naturalmente na Caatinga, especialmente associada ao Rio São Francisco, em várzeas inundáveis e encostas úmidas do pantanal matogrossense, o pajeuzeiro é uma árvore que tem importância destacada na ornamentação, medicina popular, fornecimento de madeira e restauração de áreas degradadas. Os mecanismos utilizados pelo pajeuzeiro para sobreviver em situações de déficit hídrico ainda são escassos. Diante disto, o presente trabalho teve o objetivo de investigar alterações fisiológicas e bioquímicas do pajeuzeiro quando submetido ao déficit hídrico, assim como sua capacidade de recuperação após a reidratação, tendo esta acontecido quando a fotossíntese aproximava-se de zero. Para isto, foi realizado um experimento em casa de vegetação, em delineamento inteiramente casualizado, com quatro tratamentos de reposição de água perdida por evapotranspiração (T100 – controle; T50 – 50%; T25 - 25% e T0 – sem reposição), com seis repetições cada, avaliando-se a cada 7 dias durante 28 dias. Foram avaliados o potencial hídrico foliar (Ψw), teor relativo de água (TRA), tolerância protoplasmática foliar, trocas gasosas (gs, E, A e EUA), além da fluorescência da clorofila a. Para as análises bioquímicas, analisou-se o teor de pigmentos fotossintéticos (Chl a, Chl b, Chl total e carotenoides), proteínas solúveis, prolina livre e carboidratos. O Pajeuzeiro demonstrou ter sido afetado pelo déficit hídrico, com redução significativa em relação ao T100 no Ψw e TRA para o T0, T25 e T50. Além destas, também foram verificadas reduções significativas na condutância estomática (gs), transpiração (E), taxa fotossintética (A), eficiência quântica do PSII (Fv/Fm), área e índice de performance (PIABS) nos tratamentos sob déficit hídrico. À medida que o déficit hídrico se intensificava, foi observado um aumento no percentual de danos de membrana, tendo o T0 apresentado o maior índice de danos em relação ao controle. A restrição na disponibilidade de água também afetou significativamente a concentração de pigmentos fotossintéticos, com reduções para a chl a, b e total e incremento para carotenóides. Além disso, o déficit promoveu aumento significativo na concentração de proteínas solúveis para o T0 e T25 e de prolina livre para os três tratamentos com deficiência hídrica. Para a concentração de carboidratos, houve incremento, porém não significativo. O pajeuzeiro foi bastante afetado pelo déficit hídrico, porém demonstrou forte capacidade de recuperação de todos os parâmetros analisados após a reidratação, o que demonstra certo grau de tolerância da espécie. Portanto, a espécie Triplaris gardneriana utiliza o fechamento estomático, juntamente com a senescência e abscisão foliar, como principal mecanismo para evitar a perda excessiva de água. / São Cristóvão, SE

Orientador: Rafael Silva Oliveira / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-16T23:35:55Z (GMT). No. of bitstreams: 1 Lima_AlineLopese_M.pdf: 3394396 bytes, checksum: 696ed48aed8374dfcb4e215ad3c94135 (MD5) Previous issue date: 2010 / Resumo: Eventos de neblina constituem uma importante fonte de água em vários ecossistemas terrestres, pois molham as superfícies foliares das plantas sem aumentar significativamente o conteúdo de água no solo. A água interceptada pode escoar ou ser absorvida diretamente pelas folhas inclusive de espécies lenhosas. No entanto, pouco se sabe sobre o papel ecológico desse processo e os mecanismos e estruturas envolvidos no transporte de água do exterior para os tecidos foliares, especialmente em espécies tropicais. Nesse contexto, avaliamos as vias anatômicas envolvidas na absorção de água pelas folhas e elucidamos as consequências desse processo no desempenho ecofisiológico, crescimento e sobrevivência de três espécies lenhosas comuns em matas nebulares do sudeste brasileiro, Drimys brasiliensis, Eremanthus erythropappus e Myrsine umbellata. Experimentos com água deuterada e sais traçadores apoplásticos mostraram que as espécies são capazes de obter água diretamente pelas folhas. A absorção foliar pode contribuir em até 42% do conteúdo de água das folhas em D. brasiliensis, que inclusive apresentou fluxo reverso de seiva e menores taxas de transpiração noturna quando expostas à neblina. A água pode difundir diretamente pelas cutículas foliares em todas as espécies. Os tricomas tectores de E. erythropappus e os tricomas glandulares peltados de M. umbellata parecem ser estruturas importantes para a absorção de água nessas espécies. Após transpor a barrreira cuticular, as soluções podem difundir pelas vias apoplásticas da epiderme e do parênquima das folhas das três espécies e atingir o xilema de E. erythropappus e acumular nas células coletoras de M. umbellata. A alta concentração de compostos hidrofílicos nos tecidos foliares de D. brasiliensis e M. umbellata pode ter contribuído na retenção das soluções no mesofilo destas espécies. A borrifação de ramos causou aumento imediato do status hídrico foliar nas espécies, benefício também observado em um experimento de longa duração. Após dois meses, plantas das três espécies que receberam neblina exclusivamente na parte aérea apresentaram maior potencial hídrico, fotossíntese e condutância estomática em comparação às plantas do tratamento de seca em casa de vegetação. D. brasiliensis apresentou 100% de mortalidade após um mês no tratamento de seca. O conteúdo relativo de água no solo das plantas dessa espécie sob neblina manteve-se constante ao longo do experimento, indicando que a neblina pode ter sido usada como fonte de água transpirada neste período. E. erytropappus foi a única espécie que manteve taxas de crescimento e sobrevivência semelhantes entre os tratamentos, sendo que e os benefícios da nebulização só se tornaram evidentes no final do segundo mês. O conteúdo de água no solo das plantas de M. umbellata foi reduzido nos tratamentos de neblina e seca, mas não observamos reduções no potencial hídrico, condutância estomática e fotossíntese. Estes dados sugerem que a absorção de água pelas folhas desta espécie causou um desacoplamento das relações hídricas foliares e das trocas gasosas em relação à disponibilidade de água no solo. Demonstramos que durante eventos de neblina, as três espécies lenhosas de matas nebulares tropicais podem absorver água diretamente pelas folhas. Este processo favorece a hidratação, o desempenho ecofisiológico, o crescimento e a sobrevivência das plantas, mesmo sob baixa disponibilidade de água no solo. / Abstract: Fog deposition is an important water source in several terrestrial ecosystems. Fog water intercepted by the plants can run off to the soil or be absorbed by the leaves. However, very little is known about the ecological role of fog and the mechanisms and structures involved in foliar water uptake by woody species in tropical environments. In this context, we investigated the anatomical pathways involved in the process of foliar uptake of water and evaluated the consequences of this process in the ecophysiological performance, growth and survival of three common woody species from Brazilian cloud forests: Drimys brasiliensis, Eremanthus erythropappus e Myrsine umbellata. Greenhouse experiments using artificial fog enriched in deuterium and labelling experiments with fluorescent apoplastic tracers demonstrated that the three species absorbed water directly through their leaf surfaces. Leaf water uptake contributed to as much as 42% of total foliar water content in D. brasiliensis. Fog exposition caused reversals in sap flow and reduced nighttime transpiration for this species. Water diffused directly through leaf cuticles in all species. Tector trichomes of E. erythropappus and glandular peltate trichomes of M. umbellata are important pathways for water uptake in these species. After the cuticular barrier was transposed, solutions moved through apoplast routes at the epidermis and parenchyma in all species, reaching the xylem in E. erythropappus and accumulating on collector cells of M. umbellata. The high abundance of hidrofilic compounds found on leaf surfaces of D. brasiliensis and M. umbellata may have contributed to the great retention of solution with apoplastic tracers in the mesophyll of these species. Sprayed water on isolated branches caused an immediate increase in leaf water status in the three species, a benefit also observed in a long-term experiment. After two months, plants under the fog treatment improved leaf water potential, photosynthesis and stomatal conductance in relation to plants exposed to drought in a greenhouse experiment. Species responses to the treatments were different. D. brasiliensis had 100% mortality after a month under drought. Soil water content (SWC) of fogged plants was constant throughout the experiment, suggesting that fog water might have been used as the main water source for transpiration during this period. E. erytroppappus was the only species with similar growth and survival rates in all treatments and the beneficial effects of fog water was only observed after two months. For M. umbellata, SWC decreased substantially in the drought and fog treatments but no decrease in water potential, photosynthesis and stomatal conductance was observed. For this species, fog water deposition caused a decoupling of foliar water relations and gas exchange from soil water availability.We demonstrated that the three cloud forest woody species can absorb water directly through their leaves during fog deposition, allowing shoot rehidratation and improving ecophysiological performance, growth and survival when soils are dry. / Mestrado / Biologia Vegetal / Mestre em Biologia Vegetal

Salinity continues to be one of the world’s most serious environmental problems in agriculture. The increasing world population and urbanization are forcing farmers to utilize marginal lands as well as poor quality water. One of the strategies in dealing with salinity is growing salt tolerant plants and there has been increased need to understand the effects of salinity on crops. Owing to its high nutritive value and wide adaptability to diverse environments, amaranth is considered a promising crop for marginal lands and semiarid regions. The objective of the study was to investigate the response of amaranth to salinity stress and evaluate stress amelioration by calcium and seed priming. Salinity tolerance during germination and early seedling growth was examined for six genotypes of amaranth (Amaranthus species) at different salt concentrations ranging from 0 to 200 mM NaCl or Na2SO4. Enhancement of germination was observed at 25 mM, while increasing salt concentrations reduced the germination percentage as well as germination rate. A.tricolor and Accession ’83 were able to germinate in 200 mM NaCl while there was no germination at 200 mM Na2SO4 in all the genotypes. Overall, Accession ’83 was the most resistant and A. hybridus the most sensitive genotype, particularly at high salt concentrations. Inhibition of germination was greater in Na2SO4 than in NaCl salinity treatments. Amaranth was more salt tolerant at germination than at seedling growth. Seedling emergence, survival and growth were reduced by salinity and at much lower concentrations than at seed germination. Differences in salt tolerance were noted among the genotypes. Salinity stress was initiated at different growth stages (cotyledon stage, 2-leaf stage and 4-leaf stage) in order to determine whether tolerance of amaranth differs with the stage of development. The treatment either continued until termination of the experiment or for 14 days at each stage. Amaranth plants were less sensitive to salinity when the stress was initiated at the 4-leaf stage. Lower salt concentrations had less detrimental effects than higher concentrations when applied at the cotyledon stage. Application of low salt concentration at cotyledon stage for 14 days did not have any effect on plant growth. The results indicate that it is feasible to use saline water for growing amaranth with minimum yield losses if salt concentration, duration of exposure and time of salinization are carefully managed. Differences in salinity tolerance among amaranth genotypes were analyzed in terms of plant survival, growth, gas exchange, water use and leaf anatomical changes. A. hypochondriacus and A. cruentus showed greater tolerance to salinity since they survived in 200 mM NaCl treatment and the reduction in growth at 50 and 100 mM was lower than that of A. tricolor and Accession ’83. A. hypochondriacus and A. cruentus were more efficient water users and partitioned photosynthates towards shoot growth as opposed to the other two genotypes. Photosynthetic rate, stomatal conductance, stomatal density and apertures were reduced by salinity but were higher in A. tricolor than in A. cruentus. Salinity resulted in A. cruentus developing thicker leaves compared to A. tricolor. Productivity on saline soils can be increased by growing genotypes more tolerant to salinity. The interactive effect of salinity and water stress on amaranth plant growth was evaluated. It was found that the reduction in shoot growth was greater in plants submitted to water stress than in those submitted to salt or salt + water stress. Water use efficiency was increased while leaf water and osmotic potentials were reduced by the salinity stress treatments. In drying soil plants previously salinized had a greater degree of osmotic adjustment, so that plants were able to continue growth for a longer period compared to water stressed plants. The effect of calcium in ameliorating salt stress was investigated. Supplementary calcium, either as CaSO4 or CaCl2 ameliorated the negative effects of salinity on growth, gas exchange, membrane permeability and mineral uptake. In a separate experiment it was shown that it is feasible to mitigate the adverse effects of salinity on amaranth seed germination, seedling survival and growth by seed priming and that the positive effect of priming persisted to vegetative growth stage. Priming with CaSO4 + NaCl showed a greater positive response than priming with the individual salts. / Thesis (PhD (Plant Production andSoil Science))--University of Pretoria, 2007. / Plant Production and Soil Science / unrestricted

The seasonal changes in freezing resistance and water relations in four dwarf shrub species of Ericaceae family: Vaccinium vitis-idaea, V. myrtillus, V. uliginosum and Oxycoccus palustris in two study areas differing in altitude were studied in this work. To establish the freezing resistance, the plants were sampled eight times, to determine parameters of the water relations, the plants were sampled six times during the growing season of 2009. For the freezing resistance examination, ice nucleation temperature (exotherm) and 50 per cent lethal temperature (LT50) were found. The water relations were described using the parameters derived from the pressure-volume curves: osmotic potential at full turgor, osmotic potential at zero turgor, cytoplasmic water fraction, relative water content at turgor loss and bulk modulus of elasticity. An important seasonal variability in the freezing resistance was found. The highest levels of the freezing resistance were reached in the spring and in the autumn, the lowest levels were found in the summer. There were also changes in the used mechanisms of the freezing resistance - for most of the year, the plants were tolerant, they showed the avoidance mechanism only in the summer. The seasonal changes in the water relation parameter were less unambiguous. The most of...