No description available.

There is an increasing trend towards advancing the understanding and development of ethylene oligomerization catalysts, both in academia and industry. The metal of choice in this chemistry is invariably chromium, which has shown great versatility in selective trimerization/tetramerization, non-selective oligomerization and polymerization of ethylene. While much success has been achieved in ethylene trimerization, the same con not be said about tetramerization catalysis. Aminophosphine based ligands have demonstrated their ability towards selective 1-octene production, however, the popular PNP catalyst is able to achieve only 70% selectivity. In order to explore the possibility of developing and enhancing the selectivity of chromium based ethylene tetramerization catalyst, this thesis work was undertaken. The ligand systems we chose for our work were bidentate aminophosphine based (PN(CH2)nNP), which has yielded interesting selective oligomerization. Subtle modifications were found to result in drastic changes in selectivity, from tetramerization (PN(CH2)3NP) to trimerization (PN(CH2)2NP). We managed to successfully develop the first truly selective (over 90%) 1-octene catalyst with polymer-free behavior. Further modifications on the ligand framework, where one atom of Si was used to link the two NP units, resulted in non-selective oligomerization, in which case we determined that the oxidation-state of chromium is a key player. We explored other modifications on our selective ligands in which one of the arms on the bidentate ligand was replaced with a base-donor amine, phosphine or pyridine, and resulted in interesting selectivity changes. The final modification that we tested was a novel N(CH2)2P ligand and found it to be a highly active, non-selective oligomerization catalyst.

There is an increasing trend towards advancing the understanding and development of ethylene oligomerization catalysts, both in academia and industry. The metal of choice in this chemistry is invariably chromium, which has shown great versatility in selective trimerization/tetramerization, non-selective oligomerization and polymerization of ethylene. While much success has been achieved in ethylene trimerization, the same con not be said about tetramerization catalysis. Aminophosphine based ligands have demonstrated their ability towards selective 1-octene production, however, the popular PNP catalyst is able to achieve only 70% selectivity. In order to explore the possibility of developing and enhancing the selectivity of chromium based ethylene tetramerization catalyst, this thesis work was undertaken. The ligand systems we chose for our work were bidentate aminophosphine based (PN(CH2)nNP), which has yielded interesting selective oligomerization. Subtle modifications were found to result in drastic changes in selectivity, from tetramerization (PN(CH2)3NP) to trimerization (PN(CH2)2NP). We managed to successfully develop the first truly selective (over 90%) 1-octene catalyst with polymer-free behavior. Further modifications on the ligand framework, where one atom of Si was used to link the two NP units, resulted in non-selective oligomerization, in which case we determined that the oxidation-state of chromium is a key player. We explored other modifications on our selective ligands in which one of the arms on the bidentate ligand was replaced with a base-donor amine, phosphine or pyridine, and resulted in interesting selectivity changes. The final modification that we tested was a novel N(CH2)2P ligand and found it to be a highly active, non-selective oligomerization catalyst.

There is an increasing trend towards advancing the understanding and development of ethylene oligomerization catalysts, both in academia and industry. The metal of choice in this chemistry is invariably chromium, which has shown great versatility in selective trimerization/tetramerization, non-selective oligomerization and polymerization of ethylene. While much success has been achieved in ethylene trimerization, the same con not be said about tetramerization catalysis. Aminophosphine based ligands have demonstrated their ability towards selective 1-octene production, however, the popular PNP catalyst is able to achieve only 70% selectivity. In order to explore the possibility of developing and enhancing the selectivity of chromium based ethylene tetramerization catalyst, this thesis work was undertaken. The ligand systems we chose for our work were bidentate aminophosphine based (PN(CH2)nNP), which has yielded interesting selective oligomerization. Subtle modifications were found to result in drastic changes in selectivity, from tetramerization (PN(CH2)3NP) to trimerization (PN(CH2)2NP). We managed to successfully develop the first truly selective (over 90%) 1-octene catalyst with polymer-free behavior. Further modifications on the ligand framework, where one atom of Si was used to link the two NP units, resulted in non-selective oligomerization, in which case we determined that the oxidation-state of chromium is a key player. We explored other modifications on our selective ligands in which one of the arms on the bidentate ligand was replaced with a base-donor amine, phosphine or pyridine, and resulted in interesting selectivity changes. The final modification that we tested was a novel N(CH2)2P ligand and found it to be a highly active, non-selective oligomerization catalyst.

O mamão é um fruto climatérico, cujas transformações resultantes do amadurecimento ocorrem rapidamente após a colheita. O tratamento com 1- metilciclopropeno (1-MCP) tem sido testado para ampliar sua vida útil, entretanto, com resultados até então pouco consistentes. Pesquisas com peras, bananas e ameixas foram realizadas utilizando conjuntamente 1-MCP e etileno, com resultados relevantes. Portanto, o objetivo deste trabalho foi estudar a fisiologia e a conservação pós-colheita do mamão Golden, submetido a diferentes combinações de 1-MCP e etileno, aplicados simultaneamente. Os frutos foram colhidos em pomares comerciais no estádio 1 de maturação, tratados e armazenados em câmaras frias a 11 e a 22ºC. O projeto foi dividido em três etapas. Na primeira etapa, observou-se que doses de 100 e 200 nL.L-1 de etileno combinados com iguais concentrações de 1-MCP, apresentaram resultados semelhantes aos do 1-MCP aplicado isoladamente. Na segunda etapa, o etileno nas concentrações entre 0 e 10 SL.L-1 foi combinado com 100 nL.L-1 de 1-MCP. Esse aumento na concentração de etileno diminuiu ou até mesmo anulou a ação do 1-MCP, nas concentrações mais elevadas. A mudança de cor e a perda da firmeza foram mais lentas nos tratamentos com 1-MCP na dose de 100 nL.L-1, aplicado sozinho ou associado a menor dose de etileno (2,5 SL.L-1). Estes mesmos tratamentos apresentaram atividade respiratória e produção de etileno menores que o controle. Na terceira etapa, os frutos tratados apenas com 1-MCP e 1-MCP mais etileno nas doses de 1 e 2,5 SL.L-1, mostraram maior retenção da firmeza externa, firmeza interna e cor da casca. A aparência também foi melhor nestes tratamentos, com menor porcentagem de frutos podres. O teor de sólidos solúveis foi semelhante em todos os tratamentos e o de ácido ascórbico foi mais elevado nos frutos tratados apenas com 1-MCP. A produção de etileno e a concentração de etileno endógeno foram maiores nos frutos que receberam apenas 1-MCP. A atividade respiratória e a concentração de CO2 endógeno mostraram pouca variação entre os tratamentos, durante o armazenamento. O teor de carotenóides foi menor nos tratamentos que receberam as maiores doses de etileno. O teor de clorofila foi maior no tratamento que recebeu apenas 1-MCP o qual levou mais tempo para tornar-se amarelo. A atividade da enzima pectinametilesterase (PME) foi menor nos tratamentos com 1-MCP e 1-MCP mais etileno na dose de 1 SL.L-1. A atividade das enzimas 1-aminociclopropano-1- carboxílico sintase (ACS) e oxidase (ACO) alternaram períodos de elevada e de baixa atividade em todos os tratamentos, durante o armazenamento. A aplicação simultânea de 1-MCP e do etileno mostrou resultados promissores no controle do amadurecimento do mamão Golden. / Papaya is a climacteric fruit which ripening resulting transformations occur rapidly after harvest. Treatment with 1-methylcyclopropene (1-MCP) has been tested to extend its shelf life, however, with inconsistent results so far. Researches with pears, bananas and plums were carried out using 1-MCP and ethylene with relevant results. Therefore, the aim was to study the physiology and postharvest storage of \'Golden\' papaya subjected to different combinations of 1-MCP and ethylene applied in the same time. The fruits were harvested from commercial orchards in stage 1 of ripening, they were treated and stored in cold chambers. The study was divided into three stages. In the first step it was observed that doses of 100 and 200 nL.L-1 of ethylene combined with equal concentrations of 1-MCP showed similar results to the 1-MCP applied alone. In the second step, ethylene concentrations between 0 and 10 L.L-1 were combined with 100 nL.L-1 of 1-MCP. This increase in ethylene concentrations, decreased or even nullified the action of 1-MCP. The change in color and the firmness loss were slower in the treatments using 100 nL.L-1 of 1-MCP applied alone or associated with a lower dose (2.5 L.L-1) of ethylene. These same treatments showed less respiratory activity and ethylene production than the control. In the third step, the fruits treated only with 1-MCP and 1-MCP more ethylene at the doses of 1 and 2.5 L.L-1, showed higher retention of external and internal firmness and the green color of peel. The appearance was also better in these treatments, with a lower percentage of rotten fruit. The soluble solids content was similar for all treatments and the ascorbic acid was higher in the fruits treated only with 1-MCP. The ethylene production and endogenous ethylene concentration was higher in fruits treated only with 1-MCP. Respiratory activity and endogenous CO2 concentration showed few variation among the treatments during the storage. The carotenoid content was lower in the treatments that received the highest doses of ethylene. The chlorophyll content was higher in treatments with only 1-MCP, which took longer to become yellow. The pectinmethylesterase (PME) enzyme activity was lower in treatments only with 1-MCP and 1-MCP more ethylene at a dose of 1 L.L-1. The 1- aminocyclopropane-1-carboxylic acid synthase (ACS) and oxidase (ACO) enzyme activity, alternate periods of high and low activity in all treatments during storage. Simultaneous application of 1-MCP and ethylene showed promising results in the ripening of papaya \'Golden\'.

O mamão é um fruto climatérico, cujas transformações resultantes do amadurecimento ocorrem rapidamente após a colheita. O tratamento com 1- metilciclopropeno (1-MCP) tem sido testado para ampliar sua vida útil, entretanto, com resultados até então pouco consistentes. Pesquisas com peras, bananas e ameixas foram realizadas utilizando conjuntamente 1-MCP e etileno, com resultados relevantes. Portanto, o objetivo deste trabalho foi estudar a fisiologia e a conservação pós-colheita do mamão Golden, submetido a diferentes combinações de 1-MCP e etileno, aplicados simultaneamente. Os frutos foram colhidos em pomares comerciais no estádio 1 de maturação, tratados e armazenados em câmaras frias a 11 e a 22ºC. O projeto foi dividido em três etapas. Na primeira etapa, observou-se que doses de 100 e 200 nL.L-1 de etileno combinados com iguais concentrações de 1-MCP, apresentaram resultados semelhantes aos do 1-MCP aplicado isoladamente. Na segunda etapa, o etileno nas concentrações entre 0 e 10 SL.L-1 foi combinado com 100 nL.L-1 de 1-MCP. Esse aumento na concentração de etileno diminuiu ou até mesmo anulou a ação do 1-MCP, nas concentrações mais elevadas. A mudança de cor e a perda da firmeza foram mais lentas nos tratamentos com 1-MCP na dose de 100 nL.L-1, aplicado sozinho ou associado a menor dose de etileno (2,5 SL.L-1). Estes mesmos tratamentos apresentaram atividade respiratória e produção de etileno menores que o controle. Na terceira etapa, os frutos tratados apenas com 1-MCP e 1-MCP mais etileno nas doses de 1 e 2,5 SL.L-1, mostraram maior retenção da firmeza externa, firmeza interna e cor da casca. A aparência também foi melhor nestes tratamentos, com menor porcentagem de frutos podres. O teor de sólidos solúveis foi semelhante em todos os tratamentos e o de ácido ascórbico foi mais elevado nos frutos tratados apenas com 1-MCP. A produção de etileno e a concentração de etileno endógeno foram maiores nos frutos que receberam apenas 1-MCP. A atividade respiratória e a concentração de CO2 endógeno mostraram pouca variação entre os tratamentos, durante o armazenamento. O teor de carotenóides foi menor nos tratamentos que receberam as maiores doses de etileno. O teor de clorofila foi maior no tratamento que recebeu apenas 1-MCP o qual levou mais tempo para tornar-se amarelo. A atividade da enzima pectinametilesterase (PME) foi menor nos tratamentos com 1-MCP e 1-MCP mais etileno na dose de 1 SL.L-1. A atividade das enzimas 1-aminociclopropano-1- carboxílico sintase (ACS) e oxidase (ACO) alternaram períodos de elevada e de baixa atividade em todos os tratamentos, durante o armazenamento. A aplicação simultânea de 1-MCP e do etileno mostrou resultados promissores no controle do amadurecimento do mamão Golden. / Papaya is a climacteric fruit which ripening resulting transformations occur rapidly after harvest. Treatment with 1-methylcyclopropene (1-MCP) has been tested to extend its shelf life, however, with inconsistent results so far. Researches with pears, bananas and plums were carried out using 1-MCP and ethylene with relevant results. Therefore, the aim was to study the physiology and postharvest storage of \'Golden\' papaya subjected to different combinations of 1-MCP and ethylene applied in the same time. The fruits were harvested from commercial orchards in stage 1 of ripening, they were treated and stored in cold chambers. The study was divided into three stages. In the first step it was observed that doses of 100 and 200 nL.L-1 of ethylene combined with equal concentrations of 1-MCP showed similar results to the 1-MCP applied alone. In the second step, ethylene concentrations between 0 and 10 L.L-1 were combined with 100 nL.L-1 of 1-MCP. This increase in ethylene concentrations, decreased or even nullified the action of 1-MCP. The change in color and the firmness loss were slower in the treatments using 100 nL.L-1 of 1-MCP applied alone or associated with a lower dose (2.5 L.L-1) of ethylene. These same treatments showed less respiratory activity and ethylene production than the control. In the third step, the fruits treated only with 1-MCP and 1-MCP more ethylene at the doses of 1 and 2.5 L.L-1, showed higher retention of external and internal firmness and the green color of peel. The appearance was also better in these treatments, with a lower percentage of rotten fruit. The soluble solids content was similar for all treatments and the ascorbic acid was higher in the fruits treated only with 1-MCP. The ethylene production and endogenous ethylene concentration was higher in fruits treated only with 1-MCP. Respiratory activity and endogenous CO2 concentration showed few variation among the treatments during the storage. The carotenoid content was lower in the treatments that received the highest doses of ethylene. The chlorophyll content was higher in treatments with only 1-MCP, which took longer to become yellow. The pectinmethylesterase (PME) enzyme activity was lower in treatments only with 1-MCP and 1-MCP more ethylene at a dose of 1 L.L-1. The 1- aminocyclopropane-1-carboxylic acid synthase (ACS) and oxidase (ACO) enzyme activity, alternate periods of high and low activity in all treatments during storage. Simultaneous application of 1-MCP and ethylene showed promising results in the ripening of papaya \'Golden\'.

Fruit of Capsicum annuum L. (capsicum or pepper) are one of the major sources of red food colourant and pungency for spice production. In the spice production industry, fruit are mechanically harvested at different ripeness stages and fruit colour needs to be synchronised before being processed. However, even though capsicum ripens normally on the plant it often fails to ripen fully and turn red once harvested at the green stage. Attempts to promote ripening of harvested fruits have had limited success and the reason for this has been unclear. This project, therefore, investigated ripening behaviour on and off the plant of capsicum fruit grown in Australia and examined effects of pre- and postharvest applications on ripening of green harvested fruit. To examine ripening behaviour on and off the plant, capsicum fruit from three different cultivars (a mild paprika type cv. “Papri Queen”, a cayenne chilli cv. “Caysan”, and a sweet type bell pepper cv. “Aries”) were either allowed to ripen naturally on the plant or harvested at three different maturity stages: light green, deep green and breaker. Harvested fruit were stored individually at room temperature and several ripening characteristics including internal ethylene (C2H4) and carbon dioxide (CO2) concentration, extractable colour, 1-aminocyclopropane-1-carboxylic acid (ACC) synthase and oxidase activity, and total soluble solid content (TSSC) were studied during storage. There was very limited involvement of C2H4 during ripening of capsicum and the change in ACC synthase and ACC oxidase (two enzymes in C2H4 biosynthesis pathway) activity was not closely related to that of C2H4. However, it appeared that colour development in cv. “Papri Queen” was closely associated with what C2H4 production did occur while a climacteric-like peak of C2H4 could be observed in all fruit from cv. “Caysan”. For all three cultivars, the level of internal CO2 concentration, extractable colour and TSSC were greater in fruit ripened on the plant followed by fruit harvested at the breaker, deep green and light green stage, respectively. Fruit harvested at the light green stage failed to change colour properly and had very low levels of internal CO2 concentration and TSSC while fruit harvested from the breaker stage onwards ripened normally and developed sufficient colour for spice processing. This may suggest a role of external carbon-supply during ripening. To study the effect of the external-carbon supply during ripening, the stem of fruit were cinctured when fruit reached the light green stage and fruit were left to ripen on the plant. Cincturing delayed colour development of fruit by approximately five days but cinctured fruit were still able to turn red and develop extractable colour higher than the acceptable level of 140 ASTA units. Cincturing did not significantly alter other ripening behaviour such as CO2 concentration or TSSC. The lack of external carbon-supply is, therefore, unlikely to play a major role in the failure of green harvested fruit to ripen. To study the effect of application of plant growth regulators (both pre- and postharvest), an effective method of solution application utilising cincturing was firstly developed. Different plant growth regulator solutions including ethephon, naphthalene acetic acid, abscisic acid, jasmonic acid, sucrose, and different combinations of these were applied to fruit at the light green stage to study preharvest effects on ripening parameters during storage. Only treatment with high concentrations of ethephon increased the extractable colour higher than the acceptable level of 140 ASTA units and induced the complete degradation of chlorophyll. To study effects of postharvest application, 10 µL of various plant growth regulators was dropped into the hole created on the stem of harvested fruit for ten consecutive days. Treatment with ethephon significantly increased extractable colour and degraded chlorophyll content of fruit. Pre- and postharvest ethephon treatment strongly up-regulated Capsanthin-capsorubin synthase (Ccs) gene expression in a manner similar to the up-regulation of Ccs observed in fruit ripened on the plant. This explains the effect of C2H4 on colour development and also indicates the possible reason for the failure of green harvested fruit to ripen. However, the Ccs gene expression and chlorophyll degradation induced by ethephon was not visible until 14 days after harvest which indicated it may not be a direct effect and other signal transduction factors may be involved. When fruit are ripened on the plant, colour development may, therefore, be induced by ripening-related factors (other than C2H4) which is possibly inhibited or inactivated when fruit are harvested at the green stage. C2H4 application to fruit at this stage may help to reactivate or recover these factors which in turn induce colour development. Thus, although capsicum fruit show typical non-climacteric behaviour, C2H4 appears to be involved in some aspects of the ripening process. / http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1294648 / Thesis(Ph.D.)-- School of Agriculture, Food and Wine, 2007

The market for polyamide desalination membranes is expected to continue to grow during the coming decades. Purification of alternative water sources will also be necessary to meet growing water demands. Purification of produced water, a byproduct of oil and gas production, is of interest due to its dual potential to provide water for beneficial use as well as to reduce wastewater disposal costs. However, current polyamide membranes are prone to fouling, which decreases water flux and shortens membrane lifetime. This research explored surface modification using poly(ethylene glycol) diglycidyl ether (PEGDE) to improve the fouling resistance of commercial polyamide membranes. Characterization of commercial polyamide membrane performance was a necessary first step before undertaking surface modification studies. Membrane performance was found to be sensitive to crossflow testing conditions. Concentration polarization and feed pH strongly influenced NaCl rejection, and the use of continuous feed filtration led to higher water flux and lower NaCl rejection than was observed for similar tests performed using unfiltered feed. Two commercial polyamide membranes, including one reverse osmosis and one nanofiltration membrane, were modified by grafting PEGDE to their surfaces. Two different PEG molecular weights (200 and 1000) and treatment concentrations (1% (w/w) and 15% (w/w)) were studied. Water flux decreased and NaCl rejection increased with PEGDE graft density ([microgram]/cm2), although the largest changes were observed for low PEGDE graft densities. Surface properties including hydrophilicity, roughness and charge were minimally affected by surface modification. The fouling resistance of modified and unmodified membranes was compared in crossflow filtration studies using model foulant solutions consisting of either a charged surfactant or an oil in water emulsion containing n-decane and a charged surfactant. Several PEGDE-modified membranes demonstrated improved fouling resistance compared to unmodified membranes of similar initial water flux, possibly due to steric hindrance imparted by the PEG chains. Fouling resistance was higher for membranes modified with higher molecular weight PEG. Fouling was more extensive for feeds containing the cationic surfactant, potentially due to electrostatic attraction with the negatively charged membranes. However, fouling was also observed in the presence of the anionic surfactant, indicating hydrodynamic forces are also responsible for fouling. / text

The current work focused on defining the material science options to fabricate novel, high performing ethylene/ethane (C₂H₄/C₂H₆) separation carbon molecular sieve (CMS) dense film membranes. Three polymer precursors: Matrimid®, 6FDA-DAM and 6FDA:BPDA-DAM were used as precursors to the CMS membranes. CMS performances were tailored by way of tuning pyrolysis conditions such as the pyrolysis temperature, heating rate, pyrolysis atmosphere etc. The CMS dense film membranes showed attractive C₂H₄/C₂H₆ separation performance far exceeding the polymeric membrane performances. Semi-quantitative diffusion size pore distributions were constructed by studying the transport performance of a range of different penetrant gases as molecular sized probes of the CMS pore structure. This, in conjunction with separation performance data, provided critical insights into the structure-performance relationships of the CMS materials. The effects of testing conditions, i.e. the testing temperature, pressure and feed composition on C₂H₄/C₂H₆ separation performance of CMS dense films were also analyzed. These studies were useful not just in predicting the membrane behavior from a practical stand-point, but also in a fundamental understanding of the nature of CMS membrane separation. The study helped clarify why CMS membranes outperform polymeric membrane performance, as well as allowed comparison between CMS derived from different precursors and processing conditions. The effects on C₂H₄/C₂H₆ separation in the presence of binary gas mixture were also assessed to get a more realistic measure of the CMS performance resulting from competition and bulk flow effects. The current work thus establishes a framework for guiding research ultimately aimed at providing a convenient, potentially scalable hollow fiber membrane formation technology for C₂H₄/C₂H₆ separation

Le caoutchouc naturel (CN), a cis-1,4-polyisoprene, est produit principalement par Hevea brasiliensis. Le CN est un matériau très important pour l’industrie du transport et médicale. La demande en CN augmente d’année en année. Le CN est obtenu à partir du latex. Le latex s’écoule des laticifères après saignée de l’écorce des hévéas. L’éthéphon, un libérateur d’éthylène, peut être appliqué sur certains clones d’hévéa pour stimuler la production de latex. La saignée et la stimulation à l’éthéphon sont des stress de récolte conduisant à la production de métabolites secondaires et par conséquence au caoutchouc. La biosynthèse et la signalisation de l’éthylène (ET) et de l’acide jasmonique (JA) jouent un rôle crucial dans la réponse aux stress de récolte. Deux gènes codant des facteurs de réponse à l’éthylène (ethylene response factor, ERF), HbERF-IXc4 et HbERF-IXc5, ont été prédits être orthologue à ERF1 d’Arabidopsis. ERF1 est considéré comme un facteur clé de la réponse de défense à travers l’intégration des voies de signalisation de l’éthylène et du jasmonate. Les transcrits de HbERF-IXc4 et HbERF-IXc5 s’accumulent dramatiquement en réponse à des traitements combinant la blessure, le méthyl jasmonate, et l’éthylène. Ces facteurs sont ainsi supposés être des régulateurs clés au croisement des voies de signalisation de l’éthylène et du jasmonate dans les laticifères. HbERF-IXc4 et HbERF-IXc5 ont plusieurs caractéristiques des facteurs de transcription révélés respectivement lors des expériences de trans-activation et de localisation subcellulaire : ils peuvent activer des éléments GCC agissant en cis des promoteurs des gènes cibles et ils sont présents au niveau du noyau.Dans cette étude, l’analyse fonctionnelle des gènes HbERF-IXc4 et HbERF-IXc5 a été effectuées par sur-expression de ces gènes sous le contrôle de deux promoteurs, 35S CaMV et HEV2.1 dans des lignées transgéniques d’Hevea obtenues par transformation génétique via Agrobacterium tumefaciens. Cette sur-expression a conduit à augmenter les effets des gènes natifs HbERF-IXc4 et HbERF-IXc5. Vingt-neuf lignées à activité GFP ont été sélectionnées sur un milieu contenant de la paromomycine. Douze lignées ont permis régénérées des plantes mais seulement dix ont produit un nombre suffisant de plantes pour réaliser les observations de phénotypage avec au total 1622 plantes transgéniques acclimatées en serre. Ces dix lignées transgéniques ont été confirmées par hybridation moléculaire de type Southern. L’observation morphologique des plants jusqu’à un an montre que les deux gènes (HbERF-IXc4 and HbERF-IXc5) favorisent une meilleure croissance, en termes de hauteur des plants, du diamètre des tiges, et du poids frais et sec des parties aériennes et racinaires, avec une plus forte vigueur et tolérance aux stress abiotiques. Les plants sur-exprimant HbERF-IXc5 ont aussi une meilleure performance que ceux sur-exprimant HbERF-IXc4. Ces résultats montrent aussi un système racinaire plus vigoureux et bien équilibré par rapport à la plante entière. Les analyses de RT-PCR en temps réel révèlent que l’expression des gènes HbERF-IXc4 et HbERF-IXc5 est plus forte dans les lignées transgéniques que la lignée sauvage. L’analyse fine des lignées HbERF-IXc5 montre aussi des modifications anatomiques (activité cambiale, nombre de cellules laticifères, amidon, et largeur du xylème).Ce travail est la première analyse fonctionnelle de facteurs de transcription chez Hevea. Des différences ont été observées entre les lignées HbERF-IXc4 et HbERF-IXc5. Comme ERF1, HbERF-IXc4 et HbERF-IXc5 doivent diriger la réponse à certains stress. HbERF-IXc5 serait un régulateur de la différentiation des laticifers. Cette étude pourrait être complétée par des analyses dans des lignées éteintes pour ces gènes, une comparaison des transcriptomes et métabolome de lignées sauvages et transgéniques, et l’identification des gènes cibles contrôlés par HbERF-IXc4 et HbERF-IXc5. / Natural rubber (NR) (cis-1,4-polyisoprene) is the main production from Hevea brasiliensis. NR is a very important industrial material for transportation, consumer, and medical. The demand for NR is increasing from year to year. NR is obtained from latex. The latex flows out from laticifers after tapping the bark. Ethephon, an ethylene releaser, can be applied on certain clones to stimulate the latex production. Tapping and ethephon stimulation are sources of harvesting stresses conducing to the production of secondary metabolites and consequent rubber. Ethylene (ET) and jasmonic acid (JA) biosynthesis and signalling pathways play a crucial role in the response to latex harvesting stress. Two Hevea ethylene response factor genes, HbERF-IXc4 and HbERF-IXc5, were predicted to be orthologue to ERF1 from Arabidopsis. ERF1 was suggested to be a key component of defence responses through the integration of ethylene and jasmonic acid signalling pathways. Transcripts of HbERF-IXc4 and HbERF-IXc5 were dramatically accumulated by combining wounding, methyl jasmonate, and ethylene treatment. These factors were assumed to be a key regulator at the crosstalk of ethylene and jasmonate signalling pathways in latex cells. HbERF-IXc4 and HbERF-IXc5 have several features of transcription factor revealed by transactivation experiment and subcellular localization, respectively: they can activate the GCC cis-acting element of promoters of target genes and are localized in nucleus, In this study, functional analysis of HbERF-IXc4 and HbERF-IXc5 genes have been carried out by overexpression under control of two promoters, 35S CaMV and HEV2.1 in transgenic Hevea lines obtained by Agrobacterium tumefaciens-mediated genetic transformation. This overexpression led to emphasize the effect of native HbERF-IXc4 and HbERF-IXc5 genes. Twenty-nine GFP-positive lines were established on paromomycin selection medium. Twelve lines regenerated plants but only ten led to produce a sufficient number of plants for further phenotyping with totally 1,622 transgenic plants in greenhouse. These ten ines were confirmed as transgenic by Southern blot hybridization. Observation of morphology until one year showed both genes (HbERF-IXc4 and HbERF-IXc5) promoted a better growth in terms of plant height, stem diameter, and weight of aerial and root system with higher vigour and better tolerance to some abiotic stresses. Plants overexpressing HbERF-IXc5 have also a better performance than HbERF-IXc4. Data also showed a vigorous root system well balanced with regard to the whole plant. Real-time RT-PCR analyses revealed that expression of HbERF-IXc4 and HbERF-IXc5 genes was higher in transgenic lines compared to wild-type . Analysis in details of HbERF-IXc5 lines also showed some changes in anatomy (cambium activity, number of latex cells, starch, and width of xylem).This work is the first successful functional analysis of transcription factors in Hevea. Some differences have been observed between HbERF-IXc4 and HbERF-IXc5. As ERF1, HbERF-IXc4 and HbERF-IXc5 should drive the response to some stresses. HbERF-IXc5 might be a regulator of laticifer differentiation. This study could be completed with analysis of silenced transgenic lines, comparison of transcriptome, metabolome of wild-type and transgenic lines, and identification of target genes controlled by HbERF-IXc4 and HbERF-IXc5.