La réponse et l’adaptation des plantes à un stress métallique mettent en jeu de nombreux mécanismes afin de limiter les effets néfastes des éléments toxiques. Bien que certains de ces mécanismes soient bien caractérisés, de nombreux acteurs cellulaires et moléculaires restent à identifier pour mieux comprendre la diversité des stratégies mises en œuvre dans ces processus complexes et vitaux pour les plantes.Dans un premier temps, nous nous sommes intéressés au rôle de deux modifications post-traductionnelles, la phosphorylation et la méthylation des protéines non-histone dans la réponse à un stress induit par deux éléments non essentiels et toxiques, le cadmium (Cd) et l’uranium (U). Nous avons analysé la dynamique de ces modifications chez trois espèces du genre Arabidopsis : A. thaliana et A. lyrata, deux espèces sensibles au Cd, et A. halleri, espèce naturellement capable de tolérer et d’hyper-accumuler ce métal toxique dans ses feuilles. En utilisant une combinaison d’analyses par Western blot et par spectrométrie de masse nous avons montré que les patterns de méthylation des protéines changent au cours de stress métalliques. Puis, nous avons analysé l’expression des gènes codant les enzymes impliquées dans les réactions de phosphorylation et méthylation des protéines dans différentes conditions de stress. Ces analyses ont montré qu’un grand nombre de protéines kinases sont régulés au niveau transcriptionnel par un stress métallique tandis que seules quelques une en ce qui concerne la méthylation. Pour finir, nous avons mis en place un criblage génétique de mutants d’A. thaliana et identifié deux gènes codant des protéines lysine méthyltransférases impliqués dans la tolérance au Cd.Dans un deuxième temps, nous avons étudié les mécanismes cellulaires de la réponse du système racinaire d’A. thaliana lors d’une exposition à l’U. L’utilisation de différents systèmes rapporteurs et la mesure de différents paramètres physiologiques nous ont permis de mettre en évidence que l’architecture racinaire est fortement modulée en réponse à l’U et ceci de façon dose dépendante. Cet effet est lié à l’inhibition du cycle cellulaire et à la synthèse d’espèces réactives de l’oxygène et d’oxyde nitrique dont l’accumulation provoque la mort cellulaire. Ces changements sont associés à une perturbation du transport et de la distribution de l’auxine dans les racines. Ces événements sont temporellement corrélés avec l’accumulation de polymères de défense (callose et lignine) impliqués dans l’imperméabilisation des cellules et des parois. Cette étude confirme enfin que le stress induit par l’U est intimement lié à une perturbation de l’homéostasie de certains macronutriments (phosphate et fer) et partage les cascades de signalisation d’une carence en phosphate.Ce travail met en évidence des mécanismes de réponse et d’adaptation aux métaux toxiques à travers la régulation fine des phénomènes de méthylation des protéines non-histone et l’identification de processus cellulaires impliqués dans la réponse à la toxicité de l’U dans le système racinaire. / Plant response and adaptation to metallic stress are involving numerous mechanisms limiting the toxic effect of metals. Although a large number of these mechanisms are well characterized, many processes are in need to be identified in order to have a better understanding of strategies involved in plant response to toxic elements.In first instance, we investigated the role of two post-translational modifications, phosphorylation and methylation of non-histone proteins in response to stress induced by two toxic metals, cadmium and uranium. We analyzed the dynamic of these modifications in three species of Arabidopsis: A. thaliana, A. lyrata two species sensitive to cadmium and A. halleri, a species which naturally tolerate and hyperaccumulate toxic metals in her leaves. By using Western blots and mass spectrometry in parallel, we showed that lysine methylation pattern were changing during metallic stresses. Next, we analyzed the gene expression of enzymes involved in phosphorylation and lysine methylation processes in plants exposed to different adverse conditions. These analyses showed that numerous kinases expressions were differentially regulated in response to metallic stress. Concerning protein lysine methyltransferases, only a few enzymes were differentially regulated. Finally, through a mutant genetic screening we identified two genes coding for protein lysine methyltransferases involved in tolerance to a stress induced by cadmium.Secondly, we studied the physiological and cellular processes involved in the response of A. thaliana root system to uranium. Through the utilization of several reporters and the measure of physiological parameters, we demonstrated that the root architecture was strongly modulated in response to a stress induced by uranium and that in a dose dependent manner. These effects are linked to a cell cycle inhibition and the synthesis and accumulation of reactive oxygen species and nitric oxyde wich participated in the root apex cell death. These changes were associated with perturbation in auxin transport and distribution at the root apex and were temporally correlated to the deposition of defense polymers (callose and lignin) involved in cell proofing and cell wall stiffness. This study is confirming the fact that uranium induced stress is intimately linked to a disruption of phosphate and iron homeostasis. Furthermore, uranium-signaling cascade are sharing a part of the phosphate starvation-signaling cascade.Together, these two studies are revealing mechanisms involved in plant response and adaptation to metallic trace elements through the thin tuning of non-histone methylation and the identification of cellular process involved in the toxicity of uranium in roots.

Master of Science / Department of Animal Sciences and Industry / Michael D. Tokach / A total of 5,212 nursery pigs were used in 11 experiments to evaluate amino acids in nursery pig diets. Experiments 1 and 2 were conducted to determine whether the Lys level fed during one phase of the nursery influenced the response to Lys during subsequent phases. Experiment 1 tested a wide range of dietary Lys in 2 phases and reported that pigs fed high Lys during each period had increased growth performance; however, compensatory growth occurred for the pigs previously fed low Lys diets, resulting in no impact on overall ADG or final BW. Experiment 2 tested a narrow range of dietary Lys in 3 phases and found that marginally deficient diets can be fed in the early nursery phases without influencing final BW or the response to Lys levels in subsequent phases. Both experiments demonstrate that the low dietary Lys levels used in each can be fed in the early nursery phases with no negative impact on overall nursery growth rate provided that adequate levels are fed thereafter. Experiments 3 to 6 were conducted to determine the standardized ileal digestible (SID) Lys requirement of nursery pigs from 7- to 14-kg. Data from all experiments were combined and break-point and quadratic broken-line analysis was used to determine the estimated SID Lys requirement. The SID Lys requirement for optimal growth was at least 1.30% for ADG and 1.37% for G:F, or at least 3.86 and 4.19 g SID Lys/Mcal ME, respectively. Experiments 7 to 11 were conducted to evaluate the effect of replacing specialty protein sources with crystalline AA and AA requirements for 7- to 12-kg pigs. Experiment 7 demonstrated that crystalline AA can be used to replace fish meal in diets with no negative effects on growth performance. Experiment 8 demonstrated that L-Trp, L-Val, and a source of non-essential AA were needed in low-CP, AA-fortified nursery diets to achieve maximum growth performance, whereas the addition of L-Ile was not required. Experiment 9 indicated that feeding greater than 7.35% total Lys:CP decreased growth performance and Exp. 10 indicated that a SID Val:Lys ratio of 65% was sufficient for optimal growth of early nursery pigs. Implementing the results from the previous experiments, Exp. 11 determined that crystalline AA in nursery pigs diets can replace high amounts of fish meal, meat and bone meal, and poultry meal when balanced for minimum AA ratios and maximum Lys:CP with no negative effect on growth performance.

Master of Science / Department of Animal Sciences and Industry / J.S. Drouillard / A series of experiments were conducted in which wheat gluten film forming solutions were modified by various means to produce films that would improve resistance to ruminal degradation. There was an interaction between pH and temperature, whereby low pH (pH 3) and high temperature (75°C) of film forming solution resulted in films that had highest resistance to microbial degradation. Strategies that proved unsuccessful in improving resistance to ruminal degradation included use of the cross-linking enzyme, transglutaminase; induction of a Maillard reaction; and increasing the time of heating film forming solutions. Utilizing HCl versus acetic acid as the means to lower the pH of the film forming solution resulted in poor film formation, which can be attributed to glutenin‟s solubility in acetic acid. When acetic acid was replaced with 25% HCl, however, no compromise in film formation was observed and ruminal degradability was not affected. In order to develop an economical and effective means of encapsulating lysine for rumen bypass, wheat gluten and corn zein were evaluated as encapsulation materials. Coating soybean meal with either wheat gluten or zein resulted in superior protection against ruminal degradation when compared to unprotected soybean meal. Compared to wheat gluten, zein was observed to have greater resistance to ruminal degradation in vitro. Lysine was encapsulated by the spray dry method with wheat gluten or zein. Results from an in vitro ammonia release experiment were inconclusive with respect to effectiveness of the encapsulation process. Wheat gluten films were approximately 59% degraded in pepsin solution. Our results suggest that 72% of the wheat gluten film will bypass the rumen and 59% of the bypass fraction of the film will be degraded in the abomasum. Wheat gluten and zein are suitable candidates for development of encapsulated nutrients for ruminal protection.

Assignment (MPhil)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: The study conducted was aiming on evaluating the influence of different levels of energy and amino acids, mainly lysine and methionine, on production performance of the layer bird. There were three treatments, namely the Control diet, a high energy, lysine and methionine diet (High spec.) and a low energy, lysine and methionine diet (Low spec.). The energy levels were 11.2 MJ/kg, 11.5 MJ/kg and 10.9 MJ/kg respectively. Lysine levels were 0.67%, 0.73% and 0.63% whereas methionine levels were 0.36%, 0.38% and 0.34% respectively. The experimental design was 3 x 4 factorial, which is 3 treatments with 4 replicates each. Results showed no significant difference (P>0.05) between treatments in egg production, egg mass, egg output, bodyweight and mortality. Feed intakes of the High spec. diet were significantly lower (P<0.05) than that of the control diet and the Low spec. diet. / AFRIKAANSE OPSOMMING: Hierdie studiestuk handeloor die evaluering van die invloed wat die verskillende vlakke van die energie en aminosure, veraiiisien en methionine op die produksie van 'n lê hoender het. Daar was gebruik gemaak van drie behandelings, naamlik die kontrole dieet, 'n hoë energie, lisien en methionien dieet (Hoë spesifikasie), en 'n lae energie, lisien en methionien dieet (Lae spesifikasie). Die energievlakke was 11.2 MJ/kg, 11.5 MJ/kg en 10.9 MJ/kg onderskeidelik. Lisienvlakke was 0.67%, 0.73% en 0.63% waarby methionienvlakke was 0.36%, 0.38% and 0.34% onderskeidelik. Die eksperimentele ontwerp was 3 x 4 fakulteitsfunksies: 3 behandelings met 4 replikas elk. Die resultate het geen noemenswaardige verskille (P>0.05) tussen die behandelinge in eierproduksie, eiergewig, eier-uitset, liggaamsgewig en mortaliteite nie. Die voerinnames van die hoë spesifikasie dieet was aansienlik laer (P<0.05) as die van die kontrole en lae spesifikasie dieet.

Among multiple interconnected pathways for L-Lysine catabolism in pseudomonads, it has been reported that Pseudomonas aeruginosa PAO1 employs the decarboxylase and the transaminase pathways. However, knowledge of several genes involved in operation and regulation of these pathways was still missing. Transcriptome analyses coupled with promoter activity measurements and growth phenotype analyses led us to identify new members in L-Lys and D-Lys catabolism and regulation, including gcdR-gcdHG for glutarate utilization, dpkA, amaR-amaAB and PA2035 for D-Lys catabolism, lysR-lysXE for putative L-Lys efflux and lysP for putative L-Lys uptake. The amaAB operon is induced by L-Lys, D-Lys and pipecolate supporting the convergence of Lys catabolic pathways to pipecolate. Growth on pipecolate was retarded in the gcdG and gcdH mutants, suggesting the importance of glutarate in pipecolate and 2-aminoadipate utilization. Furthermore, this study indicated links in control of interconnected networks of lysine and arginine catabolism in P. aeruginosa. Effect of D-amino acids and the genes involved in their metabolism are of great interest in both bacteria and mammals. D-Arg utilization in PAO1 requires the coupled dehydrogenases DauB and DauA. In this study, DauB was found to use only L-Arg as its substrate unlike its partner dehydrogenase DauA with wide substrate specificity. However, evidence from this study and previous studies suggest that the coupled enzymes DauB and DauA are unique for D-Arg catabolism. The three D-amino acid dehydrogenases DguA, DadA and DauA were found to have somewhat limited in vivo substrate specificity compared to that found in vitro tested using purified enzymes. Many studies showed that D-amino acids are toxic to bacteria. The ΔdguA, ΔdadA and ΔdauA triple mutant had two-fold lower minimum inhibition concentration of carbenicillin and tetracycline compared to wild-type PAO1. Both in the wild-type PAO1 and the triple mutant, synergy was observed between gentamicin or tetracycline (at concentrations below the MIC) and D-amino acids resulting in growth inhibition or reduction, respectively. However, no special synergistic or antagonistic effects were observed specifically in the ΔdguA, ΔdadA and ΔdauA triple mutant as compared to the wild-type PAO1 when D-amino acids were given in combination with antibiotics.

The hydrogenation of β-ketoesters over chirally modified Ni catalysts is a celebrated and thoroughly researched example of an enantioselective heterogeneous catalytic reaction. Enantioselective heterogeneous processes, although extremely attractive in terms of fewer complications in the separation of products from the catalyst, are hindered in their viability as industrial applications due to the lack of detailed knowledge on how chirality is conferred to the metal surface. Surface science techniques have afforded substantial progress into determining mechanisms between modifier, reactant and catalyst to explain the source of enantioselectivity of the system. In this study, a combination of solution and ultra-high vacuum (UHV)-based experiments allow a more realistic interpretation of the surface chemistry underpinning the catalytic reaction as the key step in achieving enantioselective performance is the adsorption of chiral modifiers from solution. The behaviour of (S)-aspartic acid and (S)-lysine on Ni{111} and their interaction with the prochiral β-ketoester methylacetoacetate is investigated in this study to understand their potential as chiral modifiers for the system. In UHV, scanning tunnelling microscopy (STM), reflection absorption infrared spectroscopy (RAIRS), and temperature programmed desorption (TPD) are used to analyse the conformation and order of the amino acids on the metal, and their thermal stability. Additionally, liquid-solid interface RAIRS and X-ray photoelectron spectroscopy (XPS) are used to examine the modified Ni surface, prepared under aqueous conditions, to give an accurate representation of the catalytic studies. It has been found highly likely that, for (S)-aspartic acid modified Ni{111}, enantioselective sites exist at step or step/kink defects, formed by corrosive leaching of the Ni substrate. Conversely, lysine appears to bind with a high sticking probability to Ni, in the form of lysine islands, and does not appear to etch the Ni chirally. Finally, similar experiments have been carried out on Au{111}, where lysine was found to chiral restructure the surface and form nanofingers, and 2D Ni clusters grown on Au{111} in order to investigate the formation of possible metal-organic frameworks.

Porphyromonas gingivalis, a gram-negative anaerobic bacterium, is implicated as a major etiological agent in the initiation and progression of severe forms of periodontal disease. It has been reported that gingivitis and periodontal disease affect roughly 50.3% and 35% of the adult population, respectively. Therefore, approximately over 85% of the adult population may suffer from some form of gingival disease. Porphyromonas gingivalis, an established periodontopathogen, requires hemin for growth. Although multiple hemin uptake systems appear to be present in this organism, their specific role in hemin uptake and virulence remains unknown. Pigmentation is thought to result from the accumulation of iron protoporphyrin IX (FePPIX) derived from erythrocyte hemoglobin. It has been observed that mutations abolishing activity of the Lys-X specific cysteine protease, Kgp, resulted in loss of black pigmentation of P. gingivalis W83; they were less virulent than their wild-type counterparts. Thus, we have observed that Kgp degradation of fibrinogen deregulates the clotting cascade, thereby minimizing the availability of free erythrocytes. Additionally, Kgp binds erythrocytes and degrades them, releasing hemoglobin. The interference with mechanisms involved in the accumulation of black pigmentation may be significant in controlling the pathogenic potential of P. gingivalis. These results suggest that Lys-gingipain protease is a principal protein involved in acquisition of hemin from hemoglobin as well as a major factor in transport, by affecting the accumulation of FePPIX on the bacterial cell surface. Microarray analysis indicates a change in the expression of key enzymes and proteins required for hemin uptake, iron storage, electron transport and oxidative stress. Therefore, interference with mechanisms involved in accumulation of black pigmentation may be significant in controlling the pathogenic potential of P. gingivalis.

Les dendrimères greffés de L-lysine (DGL) ont des applications potentielles variées (agents antibactériens, antifongiques…). Ces dendrimères greffés sont obtenus selon un procédé original, mis au point au laboratoire, basé sur la polymérisation des N-carboxyanhydrides (NCA) de L-lysine. Les travaux de recherche décrits dans ce mémoire ont pour objectif d'évaluer (i) la faisabilité des différents modes de modification des DGL et (ii) l'activité antibactérienne des nouveaux conjugués synthétisés.Le manuscrit resitue d'abord les DGL parmi les différentes catégories de polymères dendritiques décrites dans la littérature. Il développe également les applications des oligo- et poly-ethylène glycols (OEG et PEG) comme agents pour la fonctionnalisation de molécules bioactives et la synthèse de bioconjugués. L'approche expérimentale de greffage d'oligo-homoarginines (Har)n à un DGL de troisième génération (DGL-G3) est ensuite abordée. Ces entités, ont été synthétisées de manière rapide et économique en introduisant les fonctions guanidinium à partir d'un DGL de première génération (DGL-G1) par une méthode innovante. La première partie de travail est consacrée à la synthèse de ces oligomères. La possibilité de greffage ultérieure de ces derniers nécessite la synthèse préalable de bras d'espacement bifonctionnels porteurs d'une fonction amine à une des extrémités et d'une fonction aldéhyde masquée à l'autre. L'amine de cet intermédiaire est destinée à amorcer la polymérisation du Lys(Tfa)-NCA, alors que l'aldéhyde sera utilisé pour l'ancrage covalent à la plateforme DGL-G3. La seconde partie de ce travail est consacrée à la conjugaison de l'oligomère (Har)n sur la plateforme DGL selon une réaction d'amination réductrice qui a été optimisée et à la synthèse de nouveaux conjugués portant des chaînes hydrophobes. Parmi tous les conjugués DGL synthétisés, seuls les ceux portant les chaînes hydrophobes ont amélioré l'activité antibactérienne. / L-Lysine dendrigrafts (DGLs) have various potential applications (antibacterial agents, antifungal agents…). These dendrigrafts are obtained according to an original procedure elaborated in our laboratory based on the polymerization of L-lysine N-carboxyanhydrides (Lys-NCA). The investigations carried out in the present dissertation are aimed at assessing (i) the feasibility of the different ways of modification of DGLs and (ii) the antibacterial activity of the synthesized conjugates. The manuscript begins by locating DGLs among the different categories of dendritic polymers reported in the literature. It also develops the applications of oligo- and poly-ethylene (OEG and PEG) as agents for the functionalization of bioactive molecules and for bioconjugate synthesis. An approach consisting in grafting third generation DGL (DGL-G3) with oligo-homoarginines (Har)n is then described. These entities have been synthesized from a first generation DGL (DGL-G1) using an innovative strategy for the elaboration of guanidinium-rich peptides in a straightforward and cheap strategy. The first part of this work is dedicated to the oligomer synthesis. The possibility of further grafting of the latter is conditioned by the preceding access to bifunctional spacers bearing an amino group on the one end and a masked aldehyde function on the other end. The amine will enable the initiation of Lys(Tfa)-NCA polymerization, whereas the aldehyde will serve for the covalent grafting to the DGL-G3 scaffold. The second part of this work is devoted to the DGL-G3 functionalization by the (Har)n oligomer through a reductive amination strategy that has been optimized and to the synthesis of new conjugates with hydrophobic side-chains. Among all the conjugates prepared, only those having hydrophobic chains lead to an increase in antibacterial activity.

This thesis "Effect of concentrates feeding on slaughter weight and carcass composition in farmed fallow deer (Dama dama)" evaluates the influence of two different sorts of complementary food and a nutritive supplement to slaughter weight and structure of a fatted body. The literature summary is complemented with results of the experiment conducted on The Mnich Farm near Kardašova Řečice in association with The Institute of Animal Science. Ten-month fallow deers were divided into three groups. Each of them was kept separately, one (the control group No.1) was fed only by pasture, the group No.2 and No.3 were fed by complementary food consisting of barley and oat in a ratio of 2/3:1/3 in the amount of 0,4 kg per one head and day. The group No. 3 was extra served by the nutritive supplement containing protected lysine. The animals were weighted at the beginning of the experiment and in the process of slaughter at the age of sixteen months. Fifteen heads of cattle were randomly chosen from every group and they were slaughtered during three days - five at a day from each of group. The animals were transported to the slaughterhouse afterwards where the slaughter preparation was done according to the JUT´s (The Slaughter Preparation of meat stock classification) and the SEUROP´s (The System of Slaughter Preparation of meat stock classification) rules. The differences were statistically compared. Beyond the task the economical evaluation of profitability of complementary food and nutritive supplement admixture to the feeding ration and the slaughter processing effectivity has been made.

O crescente aumento da contaminação do solo por metais pesados, em especial o cádmio (Cd), associado à importância dos cereais, sendo estes nos países subdesenvolvidos e alguns em desenvolvimento a maior fonte protéica, são aspectos importantes que originaram a ideia deste estudo que procura analisar o metabolismo do aminoácido essencial lisina em milho (Zea mays), submetido à contaminação por Cd. Foram realizados vários ensaios a fim de se avaliar a atividade das principais enzimas do sistema antioxidante, a quantidade de aminoácidos solúveis totais e a atividade das enzimas da via do anabolismo e catabolismo da lisina. Os resultados foram apresentados na forma de dois capítulos. O capítulo 1 apresenta a caracterização bioquímica das plantas de milho (linhagem 161) submetidas ao estresse pelo Cd analisando-se a quantificação do metal nos diferentes tecidos vegetais, análise das principais enzimas do sistema antioxidante, quantificação de proteínas de reserva e aminoácidos solúveis totais, além da análise das principais enzimas da via da lisina. Os resultados da caracterização bioquímica mostraram que estes parâmetros avaliados não diferiram significativamente entre as plantas contaminadas e as do controle. No capítulo 2 foi realizada a análise das principais enzimas da via da lisina em um outro genótipo de milho, sendo uma variedade comercial (AL Avaré). De maneira geral, os resultados mostraram que o Cd induziu leves alterações nas atividades de algumas enzimas da via da lisina. Além disso, foram observadas diferenças entre os dois genótipos, tanto nas atividades específicas de enzimas como na quantificação de aminoácidos livres. Além dos dois capítulos, foram incluídos dois estudos complementares, que trouxeram análises adicionais ao estudo principal. O estudo complementar 1, apresenta os resultados de um estudo com plântulas de milho, de diferentes genótipos, sendo um com maiores teores de lisina (opaco2) e os outros para alta eficiência no uso de nitrogênio (EUN) e para baixa EUN. Tanto os resultados da peroxidação lipídica, quanto a quantidade de aminoácidos solúveis totais apresentaram diferenças entre os genótipos e doses de Cd utilizadas. O estudo complementar 2 apresenta alguns dados de enzimas antioxidantes, em PAGE não-desnaturante, de coleóptilos e radículas de embriões imaturos (sem a presença de endosperma) e germinados na presença de Cd. Estes dados mostraram uma nítida resposta antioxidante. Além disso, foram analisadas algumas células provenientes de radículas de sementes de milho germinada na presença de Cd, a fim de se avaliar os danos do metal sobre o DNA. Em resumo, os resultados obtidos neste estudo nos ajudaram a entender um pouco mais sobre o efeito do Cd nos processos fisiológicos e bioquímicos das plantas analisadas. Entretanto, estes dados podem ser considerados o ponto de partida para estudos mais detalhados. / The increase of soil contamination by heavy metals, especially cadmium (Cd), associated with the importance of cereals, which are the major source of protein in the underdeveloped and some developing countries, are important aspects that gave rise to the idea for this study which tries to analyze the metabolism of the essential amino acid lysine in maize (Zea mays), submitted to the contamination by Cd. Several tests were carried out to evaluate the activity of the main enzymes of the antioxidant system, the amount of total soluble amino acids and the activity of enzymes of lysine metabolism. The results were presented two chapters. Chapter 1 reports the biochemical characterization of the maize plants (a line with higher levels of lysine, L161) submitted to stress by Cd analyzing the metal quantification in different plant tissues, analysis of the main enzymes of the antioxidant system, quantification of reserve proteins and total soluble amino acids, in addition to the analysis of the main enzymes of lysine pathway The results showed that these parameters did not differ significantly between contaminated plants and those of the control. In Chapter 2 the main enzymes of lysine metabolism were analyzed in a commercial variety of maize (AL Avaré). Overall, the results showed that Cd induced slight changes in the activities of some enzymes of lysine pathway. In addition, differences were observed between the two genotypes, both in the specific activities of enzymes and on quantification of soluble amino acids. In addition to the two chapters, two complementary studies were included, which provided additional analyzes to the main study. Complementary study 1 presents the results of a study with maize seedlings of different genotypes, one with higher lysine (opaque2) and others for high efficiency in nitrogen use (EUN) and low EUN. Lipid peroxidation results and the amount of total soluble amino acids showed differences between the genotypes and the Cd concentrations used. Complementary study 2 presents some non-denaturing antioxidant enzyme data from coleoptiles and immature embryo rootlets (without the presence of endosperm) and germinated in the presence of Cd. These data showed a clear antioxidant response. In addition, some cells from germinated maize seedlings were analyzed in presence of Cd in order to evaluate the damage of the metal on the DNA. In summary, the results obtained in this study helped us to understand a little more about the effect of Cd on the physiological and biochemical processes of the plants analyzed. However, these data can be considered the starting point for more detailed studies.