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Investigations into response of potato to cadmium with special emphasis on genotypic and somaclonal variations.Ashrafzadeh, Seyedardalan January 2015 (has links)
Tuber crops such as potato (Solanum tuberosum L.) can take up high levels of soil cadmium (Cd) which can be accumulated in their tubers. Thus, they can act as vehicles for transporting Cd to human body which can seriously threaten our health due to its high toxicity. In some circumstances, consumption of potato can contribute to more than 50 percent of human dietary Cd intake. In the present research two approaches were used to probe the potential for genetic improvement to contribute towards the goal of “minimisation of Cd level in potato” which is a novel food safety strategy: (1) assess the natural occurrence of variation in Cd accumulating potential among different potato cultivars already in cultivation in New Zealand, and (2) as a proof-of-concept study to generate potato plants with improved Cd resistance from a model experimental potato cultivar Iwa based on plant cell culture-selection (in vitro breeding approach).
In the first approach, 10 New Zealand cultivars, namely Red Rascal (RR), Russet Burbank (RB), Fianna (F), Agria (A), Laura (L), Purple Heart (PH), Purple Passion (PP), Yukon Gold (YG), Moonlight (M) and Summer Delight (SD) were chosen randomly among over 30 cultivars grown for seed production in a block situated approximately one kilometre east of Lincoln, Canterbury within the 2011-2012 growing season. The tubers as well as the soil samples immediately surrounding the tubers were harvested and prepared for analytical analyses using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). The results showed that the soil samples were low in Cd level (0.06 mg kg-1), compared with the national soil average (0.35 mg kg-1), while the tubers varied widely in Cd content from 0.04 to 0.34 mg kg-1 among different cultivars. Therefore, SD with the lowest mean Cd content (0.05 mg kg-1) and an Enrichment Factor (EF) of just below one showed promise as a potential cadmium safe cultivar (CSC). There might be of concern if L, YG, PP with the highest mean Cd contents (0.18-0.21 mg kg-1) are grown in soils with higher Cd levels.
Potato tissue culture required for the second approach based on somaclonal variation was established from the model experimental genotype Iwa in the lab. Leaf and internode explants were used as the starting plant materials to initiate two morphologically distinct calli (type-A and -B). Upon morphological assessment and analysis of antioxidative enzymes such as peroxidase, it was revealed that they exhibited differential Cd sensitivity. The more Cd-resistant callus type (type-B) was chosen for in vitro selection using 18 different Cd treatments varying in Cd exposure timing and duration. Following shoot and root regeneration from these calli, 18 different new Iwa plant lines were obtained. After at least three months of sub-culturing of all 18 plant lines on Cd-free media, in vitro screening of the lines was carried out to identify the most promising plant lines as far as Cd resistance was concerned. After two rounds of in vitro growth screening under a low and high Cd levels, two lines including line 9 (L9) and line 11 (L11) were found to exhibit enhanced Cd resistance compared to control Iwa plants. Further studies of L9 and L11 compared to control Iwa plants including biochemical analysis of reactive oxygen species such as hydrogen peroxide, and transmission electron microscopic studies uncovered that L11 was more resistant to Cd than L9 and control plants. L11 plantlets had about 20 and 10 percent less H2O2 level than control and L9 plantlets, while antioxidative activities were four and two times higher in L11 compared with control and L9, respectively. Moreover, L11 seemed to exhibit a high rate of Cd compartmentalisation in the vacuoles and Cd binding to the cell walls in the roots, suggesting a potential to exclude or limit Cd translocation to other parts of the plant.
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Characterization of genotype variation and agronomic biofortification of cowpea with selenium : impacts on phytic acid and nutritional quality of grains /Silva, Vinícius Martins. January 2019 (has links)
Orientador: André Rodrigues dos Reis / Resumo: O selênio (Se) é um nutriente para humanos e animais e um elemento benéfico para as plantas, sua baixa concentração nos solos do Brasil pode gerar deficiência nos animais e humanos. O fitato é a principal forma de reserva de fósforo (P) encontrado nas sementes de plantas, sendo considerado um “anti-nutriente” por formar complexos não digeríveis com nutrientes como Fe, Ca e Zn. Desta forma, existe a necessidade de se buscar alternativas para aumentar os teores de Se e reduzir o teor de fitato nas partes comestíveis de cultivares modernos. O objetivo do trabalho foi avaliar doses e fonte ótimas de Se a serem aplicadas em condições brasileiras, bem como a influência do Se na produção e qualidade nutricional em 29 genótipos de feijão-caupi. Para isso, foram desenvolvidos dois experimentos a seguir: Experimento 1: Foi avaliada a eficiência da biofortificação agronômica utilizando 2 fontes de Se (selenato e selenito) e 7 doses de Se (0; 2,5; 5,0; 10,0; 20,0; 40,0 e 60 g ha-1) aplicados via solo, foi realizada analise de fitatos nos grãos. Experimento 2: Foi realizado um experimento para caracterizar a absorção e acúmulo de Se, teor de fitatos, açucares, proteínas de reversa e amino ácidos nos grãos de diferentes genótipos de feijão-caupi, nesse experimento, 29 genótipos foram avaliados na presença e ausência de Se (0 e 25 kg ha-1), cultivados até o final do ciclo para a obtenção dos grãos. No experimento 1, observou-se que a aplicação de selenato proporciona maiores concentrações d... (Resumo completo, clicar acesso eletrônico abaixo) / Mestre
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Micronutrientes e metais pesados tóxicos: do fertilizante ao produto agrícola / Micronutrients and toxic heavy metals: from fertilizer to agricultural productMoraes, Milton Ferreira de 27 April 2009 (has links)
A presença de metais pesados tóxicos em fertilizantes tem sido motivo de preocupação e apontada como um dos obstáculos à produção sustentável de alimentos. Por outro lado, há uma crescente busca por produtos agrícolas de melhor qualidade, com maior teor de micronutrientes e menos fatores antinutricionais, como os metais pesados tóxicos. No Brasil, há poucos trabalhos relacionando fertilização e qualidade dos produtos agrícolas, em termos de micronutrientes e metais pesados tóxicos. Neste contexto, no presente trabalho foram realizados quatro experimentos tendo como objetivos avaliar: 1) a eficiência de métodos de extração e de quantificação simultânea de micronutrientes e de metais pesados tóxicos em fertilizantes; 2) a influência da fertilização nos teores de micronutrientes e metais pesados tóxicos no solo, nos indicadores microbiológicos, nas atividades enzimáticas em plantas e na qualidade dos produtos agrícolas; 3) a variação genotípica para teor de Cd, micronutrientes e suas relações em 35 cultivares de arroz de terras altas do Brasil; 4) a influência do estado nutricional e genotípica nos teores de Cd e 70Zn no arroz. Quando se usa reagentes e água de alta pureza, a análise de metais pesados tóxicos em amostras de fertilizantes pode ser realizada por micro-ondas ou sistema aberto, sendo que as quantificações dos elementos por ICP-MS e ICP-AES produzem resultados semelhantes. Porém, na análise dos teores naturais de Cd, Cr e Pb apenas a quantificação por ICP-MS foi adequada. Nas condições deste trabalho, tanto os subprodutos e rocha fosfática quanto os fertilizantes foram capazes de fornecer nutrientes às plantas, sem causar aumentos excessivos de metais pesados tóxicos nos solos e nos produtos agrícolas. Os indicadores microbiológicos do solo e as atividades enzimáticas em plantas de alface reagiram positivamente à fertilização. Foram identificadas variedades de arroz de terras altas com baixo e alto teor de Cd nos grãos. Os teores de Fe, Zn e Se apresentaram relações inversas ao teor de Cd. Observou-se interação entre estado nutricional da planta e genótipo no teor de Cd em grãos de arroz de terras altas cultivado em solução nutritiva. Concluiu-se que, com manejo adequado, a fertilização aumenta a produtividade e melhorar qualidade dos produtos agrícolas para alimentação humana e animal / The presence of toxic heavy metals in fertilizers has been a big concern. It has been indicated as one of the obstacles to sustainable food production. On the other hand, there is a growing demand for better-quality products, with high micronutrient content and low malnutrition factors, such as toxic heavy metals. In Brazil there are scarce number of studies regarding fertilization and the quality of agricultural products for micronutrients and toxic heavy metals. In this context, the present study, involving four experiments, was conducted with the objectives: 1) to assess the efficiency of methods to extract and quantify micronutrients and toxic heavy metals in fertilizers; 2) to study the influence of fertilization on the levels of micronutrients and toxic heavy metals in agricultural products; 3) to evaluate the genotypic variation in response to the content of Cd, micronutrients and their relations in 35 upland rice cultivars from Brazil; and 4) to determine the influence of the nutritional status and genotype on the levels of Cd and 70Zn in rice plant. The results showed that with the use of reagents and water of high purity, toxic heavy metals can be extracted for analysis by microwave or an open air system, and that quantification of the elements by ICP-MS and ICP-AES yields similar results. However, for the analysis of natural contents of Cd, Cr and Pb only ICP-MS quantification was appropriate. Further, both by-products and phosphate rock, as fertilizers were able to supply nutrients to the plants without causing excessive increases of toxic heavy metals in soil and agricultural products. Microbiological soil indicators and enzyme activities in plants responded positively to fertilization. Furthermore, results also showed that there were upland rice cultivars with low and high Cd content in the grains, and the levels of Fe, Zn and Se showed inverse relations with the Cd content. There was an interaction between plants the nutritional status and genotype for Cd content in grains of upland rice cultivars. Based on the results, it can be concluded that with adequate management, fertilization can increase crop yields and improve the quality of agricultural products for human and animal consumption
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Micronutrientes e metais pesados tóxicos: do fertilizante ao produto agrícola / Micronutrients and toxic heavy metals: from fertilizer to agricultural productMilton Ferreira de Moraes 27 April 2009 (has links)
A presença de metais pesados tóxicos em fertilizantes tem sido motivo de preocupação e apontada como um dos obstáculos à produção sustentável de alimentos. Por outro lado, há uma crescente busca por produtos agrícolas de melhor qualidade, com maior teor de micronutrientes e menos fatores antinutricionais, como os metais pesados tóxicos. No Brasil, há poucos trabalhos relacionando fertilização e qualidade dos produtos agrícolas, em termos de micronutrientes e metais pesados tóxicos. Neste contexto, no presente trabalho foram realizados quatro experimentos tendo como objetivos avaliar: 1) a eficiência de métodos de extração e de quantificação simultânea de micronutrientes e de metais pesados tóxicos em fertilizantes; 2) a influência da fertilização nos teores de micronutrientes e metais pesados tóxicos no solo, nos indicadores microbiológicos, nas atividades enzimáticas em plantas e na qualidade dos produtos agrícolas; 3) a variação genotípica para teor de Cd, micronutrientes e suas relações em 35 cultivares de arroz de terras altas do Brasil; 4) a influência do estado nutricional e genotípica nos teores de Cd e 70Zn no arroz. Quando se usa reagentes e água de alta pureza, a análise de metais pesados tóxicos em amostras de fertilizantes pode ser realizada por micro-ondas ou sistema aberto, sendo que as quantificações dos elementos por ICP-MS e ICP-AES produzem resultados semelhantes. Porém, na análise dos teores naturais de Cd, Cr e Pb apenas a quantificação por ICP-MS foi adequada. Nas condições deste trabalho, tanto os subprodutos e rocha fosfática quanto os fertilizantes foram capazes de fornecer nutrientes às plantas, sem causar aumentos excessivos de metais pesados tóxicos nos solos e nos produtos agrícolas. Os indicadores microbiológicos do solo e as atividades enzimáticas em plantas de alface reagiram positivamente à fertilização. Foram identificadas variedades de arroz de terras altas com baixo e alto teor de Cd nos grãos. Os teores de Fe, Zn e Se apresentaram relações inversas ao teor de Cd. Observou-se interação entre estado nutricional da planta e genótipo no teor de Cd em grãos de arroz de terras altas cultivado em solução nutritiva. Concluiu-se que, com manejo adequado, a fertilização aumenta a produtividade e melhorar qualidade dos produtos agrícolas para alimentação humana e animal / The presence of toxic heavy metals in fertilizers has been a big concern. It has been indicated as one of the obstacles to sustainable food production. On the other hand, there is a growing demand for better-quality products, with high micronutrient content and low malnutrition factors, such as toxic heavy metals. In Brazil there are scarce number of studies regarding fertilization and the quality of agricultural products for micronutrients and toxic heavy metals. In this context, the present study, involving four experiments, was conducted with the objectives: 1) to assess the efficiency of methods to extract and quantify micronutrients and toxic heavy metals in fertilizers; 2) to study the influence of fertilization on the levels of micronutrients and toxic heavy metals in agricultural products; 3) to evaluate the genotypic variation in response to the content of Cd, micronutrients and their relations in 35 upland rice cultivars from Brazil; and 4) to determine the influence of the nutritional status and genotype on the levels of Cd and 70Zn in rice plant. The results showed that with the use of reagents and water of high purity, toxic heavy metals can be extracted for analysis by microwave or an open air system, and that quantification of the elements by ICP-MS and ICP-AES yields similar results. However, for the analysis of natural contents of Cd, Cr and Pb only ICP-MS quantification was appropriate. Further, both by-products and phosphate rock, as fertilizers were able to supply nutrients to the plants without causing excessive increases of toxic heavy metals in soil and agricultural products. Microbiological soil indicators and enzyme activities in plants responded positively to fertilization. Furthermore, results also showed that there were upland rice cultivars with low and high Cd content in the grains, and the levels of Fe, Zn and Se showed inverse relations with the Cd content. There was an interaction between plants the nutritional status and genotype for Cd content in grains of upland rice cultivars. Based on the results, it can be concluded that with adequate management, fertilization can increase crop yields and improve the quality of agricultural products for human and animal consumption
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Eficiência de uso de fósforo por cultivares de café e adaptação morfológica do sistema radicular sob deficiência do nutriente. / Phosphorus use efficiency by coffee cultivars and morphological adaptation of the root system under nutrient deficiencyPaula Neto, Ana 21 February 2014 (has links)
O fósforo (P) é um elemento essencial à produção agrícola, finito e insubstituível em suas funções no metabolismo vegetal. A baixa disponibilidade do nutriente nos solos tropicais está relacionada à sua forte interação com os colóides e íons na solução do solo, por meio da adsorção e precipitação, que reduzem a fração disponível. As plantas desenvolvem mecanismos de adaptação sob deficiência de P nos solos. Diversos estudos indicam variação genotípica das plantas em relação ao uso eficiente do nutriente. O aumento da eficiência de uso pode ser conseguida pelo aumento da aquisição do nutriente do solo (eficiência de absorção) e pelo aumento da produção por unidade de P absorvido (eficiência de utilização). Esta pesquisa foi realizada com o objetivo de caracterizar os cultivares das espécies Coffea arabica e Coffea canephora quanto ao uso de P, agrupar em relação a eficiência e resposta ao nutriente, e avaliar as adaptações morfológicas do sistema radicular do cafeeiro submetido a baixa disponibilidade de P. O crescimento do cafeeiro reduziu sob baixa disponibilidade de P, e a concentração do nutriente foi superior nos cultivares de C. canephora. As folhas jovens concentraram mais P, principalmente na forma de Pi. A colonização micorrízica em C. arabica foi superior nas raízes sob deficiência de P, e a atividade da enzima fosfatase ácida não variou com os níveis do nutriente. Os cultivares de C. canephora foram eficientes na absorção de P, enquanto os cultivares de C. arabica eficientes na utilização do nutriente. A eficiência de P variou entre os cultivares de café, em que E16 Shoa, E22 Sidamo, Iêmen e Acaiá foram eficientes e responsivos. A deficiência de P reduziu o crescimento e o acúmulo de biomassa no cafeeiro, mas aumentou a razão raiz/parte aérea em C. arabica. As raízes sob deficiência de P foram mais finas e cresceram menos. A eficiência de absorção de P correlacionou positivamente com a área superficial, comprimento, volume de raízes, número de ramificações e densidade de tecido de raiz, e negativamente com o comprimento específico. A eficiência de utilização correlacionou positivamente com a altura, número de folhas, massa seca e razão raiz/parte aérea, e negativamente com a concentração e acúmulo de P nos tecidos. Os cultivares mais eficientes em P apresentaram maior área superficial, comprimento, volume de raízes e densidade de tecido radicular, e menor comprimento específico sob deficiência do nutriente. Os cultivares mais eficientes em P foram: E22 Sidamo, Acaiá, Jimma Tane, Obatã, Ouro Verde, Caturra Amarelo, Icatu Precoce e Guarini. / Phosphorus is a nutrient essential to agricultural production, finite and irreplaceable in their functions in plant metabolism. Low P availability in tropical soils is related to its strong interaction with colloids and ions in soil solution by means of adsorption and precipitation, which reduce the fraction available. Plants develop adaptation mechanisms under P deficiency in soils. Several studies indicate genotypic variation of plants in relation to the efficient use of P. Increased use efficiency can be achieved by increasing soil nutrient acquisition (uptake efficiency) and by enhancing production per unit of P absorbed (utilization efficiency). The objective of this study was to characterize cultivars of the species Coffea arabica and Coffea canephora regarding the use of P, group them in terms of efficiency and response to P and assess the morphological adaptations of the root system of coffee cultivars subjected to low availability of P. Coffee growth reduced under low availability of P, and P concentration was higher in cultivars of C. canephora. Young leaves concentrated more P, mostly in the form of Pi. Mycorrhizal colonization of C. arabica was higher in the roots under P deficiency, and the activity of the phosphatase acid enzyme did not vary with nutrient levels. Cultivars of C. canephora were efficient in P uptake, while the cultivars of C. arabica were more efficient in nutrient utilization. P efficiency varied between the coffee cultivars, and E16 Shoa, E22 Sidamo, Iêmen and Acaiá were efficient and responsive. P deficiency reduced growth and biomass accumulation in the coffee plant, but increased the root/shoot ratio in C. arabica. Roots under P deficiency were thinner and grew less. The P uptake efficiency correlated positively with the surface area, length, root volume, number of branches and root tissue density, and negatively with the specific length. P utilization efficiency correlated positively with height, number of leaves, dry matter and root/shoot ratio, and negatively with the concentration and accumulation of P in the tissues. Cultivars that were more efficient in P uptake showed more surface area, length, root volume and root tissue density, and smaller specific length under P deficiency. The most P efficient cultivars were: E22 Sidamo, Acaiá, Jimma Tane, Obatã, Ouro Verde, Caturra Amarelo, Icatu Precoce and Guarini.
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Eficiência de uso de fósforo por cultivares de café e adaptação morfológica do sistema radicular sob deficiência do nutriente. / Phosphorus use efficiency by coffee cultivars and morphological adaptation of the root system under nutrient deficiencyAna Paula Neto 21 February 2014 (has links)
O fósforo (P) é um elemento essencial à produção agrícola, finito e insubstituível em suas funções no metabolismo vegetal. A baixa disponibilidade do nutriente nos solos tropicais está relacionada à sua forte interação com os colóides e íons na solução do solo, por meio da adsorção e precipitação, que reduzem a fração disponível. As plantas desenvolvem mecanismos de adaptação sob deficiência de P nos solos. Diversos estudos indicam variação genotípica das plantas em relação ao uso eficiente do nutriente. O aumento da eficiência de uso pode ser conseguida pelo aumento da aquisição do nutriente do solo (eficiência de absorção) e pelo aumento da produção por unidade de P absorvido (eficiência de utilização). Esta pesquisa foi realizada com o objetivo de caracterizar os cultivares das espécies Coffea arabica e Coffea canephora quanto ao uso de P, agrupar em relação a eficiência e resposta ao nutriente, e avaliar as adaptações morfológicas do sistema radicular do cafeeiro submetido a baixa disponibilidade de P. O crescimento do cafeeiro reduziu sob baixa disponibilidade de P, e a concentração do nutriente foi superior nos cultivares de C. canephora. As folhas jovens concentraram mais P, principalmente na forma de Pi. A colonização micorrízica em C. arabica foi superior nas raízes sob deficiência de P, e a atividade da enzima fosfatase ácida não variou com os níveis do nutriente. Os cultivares de C. canephora foram eficientes na absorção de P, enquanto os cultivares de C. arabica eficientes na utilização do nutriente. A eficiência de P variou entre os cultivares de café, em que E16 Shoa, E22 Sidamo, Iêmen e Acaiá foram eficientes e responsivos. A deficiência de P reduziu o crescimento e o acúmulo de biomassa no cafeeiro, mas aumentou a razão raiz/parte aérea em C. arabica. As raízes sob deficiência de P foram mais finas e cresceram menos. A eficiência de absorção de P correlacionou positivamente com a área superficial, comprimento, volume de raízes, número de ramificações e densidade de tecido de raiz, e negativamente com o comprimento específico. A eficiência de utilização correlacionou positivamente com a altura, número de folhas, massa seca e razão raiz/parte aérea, e negativamente com a concentração e acúmulo de P nos tecidos. Os cultivares mais eficientes em P apresentaram maior área superficial, comprimento, volume de raízes e densidade de tecido radicular, e menor comprimento específico sob deficiência do nutriente. Os cultivares mais eficientes em P foram: E22 Sidamo, Acaiá, Jimma Tane, Obatã, Ouro Verde, Caturra Amarelo, Icatu Precoce e Guarini. / Phosphorus is a nutrient essential to agricultural production, finite and irreplaceable in their functions in plant metabolism. Low P availability in tropical soils is related to its strong interaction with colloids and ions in soil solution by means of adsorption and precipitation, which reduce the fraction available. Plants develop adaptation mechanisms under P deficiency in soils. Several studies indicate genotypic variation of plants in relation to the efficient use of P. Increased use efficiency can be achieved by increasing soil nutrient acquisition (uptake efficiency) and by enhancing production per unit of P absorbed (utilization efficiency). The objective of this study was to characterize cultivars of the species Coffea arabica and Coffea canephora regarding the use of P, group them in terms of efficiency and response to P and assess the morphological adaptations of the root system of coffee cultivars subjected to low availability of P. Coffee growth reduced under low availability of P, and P concentration was higher in cultivars of C. canephora. Young leaves concentrated more P, mostly in the form of Pi. Mycorrhizal colonization of C. arabica was higher in the roots under P deficiency, and the activity of the phosphatase acid enzyme did not vary with nutrient levels. Cultivars of C. canephora were efficient in P uptake, while the cultivars of C. arabica were more efficient in nutrient utilization. P efficiency varied between the coffee cultivars, and E16 Shoa, E22 Sidamo, Iêmen and Acaiá were efficient and responsive. P deficiency reduced growth and biomass accumulation in the coffee plant, but increased the root/shoot ratio in C. arabica. Roots under P deficiency were thinner and grew less. The P uptake efficiency correlated positively with the surface area, length, root volume, number of branches and root tissue density, and negatively with the specific length. P utilization efficiency correlated positively with height, number of leaves, dry matter and root/shoot ratio, and negatively with the concentration and accumulation of P in the tissues. Cultivars that were more efficient in P uptake showed more surface area, length, root volume and root tissue density, and smaller specific length under P deficiency. The most P efficient cultivars were: E22 Sidamo, Acaiá, Jimma Tane, Obatã, Ouro Verde, Caturra Amarelo, Icatu Precoce and Guarini.
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The effectiveness of induced plant disease resistance: genotypic variation and quantification by chlorophyll fluorescenceTung, Jonathan 16 September 2011 (has links)
Cultivars of Agrostis stolonifera showed weak and strong responsiveness to the systemic acquired resistance (SAR) activator, benzothiadiazole (BTH), or the induced systemic resistance (ISR) activator, 2R, 3R-butanediol (BD). Next Generation RNA sequencing was used to identify 2163 putative transcripts with increased expression in BTH versus water-treated A. stolonifera. Among three BTH-induced genes, AsASP-2 and AsHIR-1 were induced faster, while AsLOX-1 had stronger transient induction, in one out of two strongly BTH-responsive cultivars. Three ISR-responsive genes, AsGNS-5, AsOPR-4 and AsAOS-1, showed no greater induction or priming in the strongly versus weakly BD-responsive cultivars. Cultivars of A. stolonifera vary significantly in their response to defense activators, however this is not consistently related to defense gene expression. To quantify disease severity, chlorophyll fluorescence imaging of the maximum quantum efficiency of photosystem II (Fv/Fm) was tested on Nicotiana benthamiana infected with Colletotrichum orbiculare. Leaf areas of healthy, non-necrotic affected and necrotic tissue could be individually quantified, which demonstrated that BD delayed symptom development by approx. 24-hour and reduced non-necrotic affected tissue compared to controls. Chlorophyll fluorescence imaging can quantify and reveal novel features about induced disease resistance.
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Wood anatomy and cytokinin-related responses in poplar (Populus sp.) under environmental stressPaul, Shanty 01 March 2017 (has links)
No description available.
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Variabilité intraspécifique de la sensibilité des macrophytes aquatiques à la contamination chimique : l'exemple du cuivre / Intraspecific variation in the sensitivity of aquatic macrophytes to chemical contamination : the case of copperRoubeau Dumont, Eva 30 November 2018 (has links)
La variabilité intraspécifique fait partie intégrante de la réponse à court et à long terme des organismes vivants aux fluctuations environnementales. Cette variabilité, exprimée au travers de différents traits des individus, peut potentiellement influencer la sensibilité des espèces à une contamination chimique. La variabilité intraspécifique n'est pas, à l'heure actuelle, prise en compte en évaluation des risques écotoxicologiques, alors même qu'elle pourrait en biaiser les résultats. Pour examiner cette hypothèse, l'importance de la variabilité intraspécifique dans la réponse au cuivre (Cu) a été quantifiée en conditions contrôlées pour trois espèces de macrophytes aquatiques, Lemna minor, Myriophyllum spicatum et Ceratophyllum demersum. Les variations entre génotypes de chacune de ces 3 espèces ont été comparées à la variabilité interspécifique. Les résultats ont mis en évidence une variabilité génotypique significative, dont l'importance dépend de l'espèce considérée. En effet, L. minor a montré une faible variabilité, au contraire de M. spicatum dont la variabilité de l'inhibition de croissance par le Cu est supérieure aux différences interspécifiques. Afin de préciser l'étendue et les mécanismes de la variabilité génotypique chez M. spicatum, d'autres expériences impliquant des mesures de traits d'histoire de vie ont été réalisées sur 7 génotypes exposés au Cu. Les résultats ont montré que certains génotypes étaient jusqu'à 8 fois plus sensibles au Cu à des concentrations allant de 0.15 à 0.5 mg/L). Ces différences de sensibilité sont en partie expliquées par les traits mesurés, mais des mesures physiologiques et/ou des approches en transcriptomique devraient pouvoir expliquer de façon plus consistante la source de ces différences de sensibilité. Enfin, 3 expériences faisant varier respectivement la teneur en nutriments, l'intensité lumineuse et la préexposition au Cu, ont démontré que la plasticité phénotypique joue un rôle majeur dans la sensibilité au Cu chez L. minor. En effet, l'affaiblissement des individus, résultant des conditions environnementales défavorables, peut conduire au doublement de la sensibilité de L. minor au Cu. [...] / Intraspecific variability plays a pivotal role in short and long term responses of species to environmental fluctuations. This variability, expressed through different traits of individuals, can potentially influence species sensitivity to chemical contamination. This intraspecific variability is currently not taken into account in ecotoxicological risk assessment, whereas it can mislead its results. To examine this hypothesis, the importance of intraspecific variability in the response to copper (Cu) was quantified in controlled conditions for three aquatic macrophyte species, Lemna minor, Myriophyllum spicatum and Ceratophyllum demersum. Variations among genotypes of each of these 3 species were compared to interspecific variability. Results have highlighted a significant genotypic variability, whose importance depends on the species considered. Indeed, L. minor demonstrated a low variability, contrarily to M. spicatum whose variability in growth inhibition by Cu was higher than interspecific differences. In order to specify the extent and the mechanisms of genotypic variability in M. spicatum, other experiments involving measurements of life-history traits have been conducted on 7 genotypes exposed to Cu. Results showed that some genotypes were up to eightfold more sensitive to Cu than others (at concentrations ranging between 0.15 and 0.5 mg/L). These differences in sensitivity were partly explained by the traits measured, but physiological or transcriptomic endpoints may explain more precisely the source of these differences in sensitivity. Finally, 3 experiments with fluctuations in nutrient concentrations, light intensity and Cu pre-exposure have demonstrated that phenotypic plasticity plays an important role in L. minor sensitivity to Cu. Indeed, the weakening of individuals, as a result of unfavorable environmental conditions, can lead to a two-fold increase in sensitivity to Cu.[...]
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