The antimycobacterial activity of twenty South African medicinal plants were investigated using two methods commonly used; the conventional agar plate method and the BACTEC radiometric method. Fourteen of the twenty acetone extracts of medicinal plants used to treat pulmonary diseases showed inhibitory activity at a concentration of 0.5 mg/ml against a sensitive strain of Mycobacterium tuberculosis using the conventional agar plate method. These fourteen extracts were also tested against M tuberculosis by the BACTEC radiometric method against a sensitive as well as a strain resistant to the drugs isoniazid and rifampin. Eight plants showed activity against both the strains at a concentration of 1.0 mg/ml. Susceptibility testing of M tuberculosis by the agar plate method is reliable, economical, and reproducible whereas the BACTEC radiometric method is much faster and probably more accurate than the agar plate method. A cytotoxicity assay of the fourteen plants on primary vervet monkey kidney cells showed that the crude acetone extracts of E. natalensis was the least cytotoxic extract with significant antimycobacterial properties. It was therefore, chosen for the isolation of active compound(s). An antibacterial assay of the water and acetone extracts of the roots of E. natalensis showed that they inhibited the growth of Gram-positive bacteria at concentrations ranging between 0.1 and 6.0 mg/ml. The water extract did not exert any inhibitory action on Gram-negative bacteria while the acetone extract showed inhibitory activity at a concentration of 5.0 mg/ml. The MIC of diospyrin, isolated from E. natalensis, was found to be 100 µg/ml for a drug-sensitive and a number of drug-resistant strains of M. tuberculosis and Gram-positive bacterial species. An antiviral investigation of the crude extracts of E. natalensis showed that the water extract of the roots of the plant inhibited the replication of herpes simplex virus type 1 moderately at a concentration of 0.2 mg/ml whereas, acetone extract at concentrations ranging from 0.1 to 0.02 mg/ml. Diospyrin exhibited no inhibitory effect against the virus. The MIC of 7-methyljuglone, isolated from E. natalensis, was found to be 50 µg/ml for both drug-sensitive and drug-resistant strains of M. tuberculosis. The compound inhibited the growth of Gram-positive bacterial species at concentrations ranging from 50 to 100 µg/ml. No inhibitory effect of the compound was observed on any Gram-negative bacteria at the highest concentration tested. A significant synergistic effect of the two naphthoquinones was observed against M tuberculosis and some of the bacterial species. MICs obtained were 10 µg/ml and 50 µg/ml for M tuberculosis and the bacterial species respectively. No synergistic effect was observed on any Gram-negative bacterial species investigated. In view of the encouraging results obtained from this study on the biological activity of the two naphthoquinones; diospyrin and 7 -methyljuglone, it appears that the compounds deserve further investigation in order to explore its potential as antimycobacterial agents. / Thesis (DPhil (Plant Physiology))--University of Pretoria, 2007. / Plant Science / unrestricted

Vegetable soybean, also known as edamame, has become increasingly popular in the United States due to its excellent nutrition and health benefits. This rising demand has sparked the interest of local farmers in growing edamame. However, a significant problem in edamame production is the poor seedling emergence. This dissertation focuses on three key objectives: 1) exploring the physiological traits linked to the low emergence of edamame seeds; 2) enhancing edamame seedling emergence by identifying genotypes with high vigor and resistance to soil-borne diseases; and 3) determining the optimal temperature for edamame seedling emergence. The study includes newly developed edamame breeding lines from the soybean breeding programs at Virginia Tech and the University of Arkansas, and major edamame cultivars commonly used in the Mid-Atlantic region. The results have identified several genotypes that exhibit high seeding vigor, aging tolerance, and consistently achieve a plant stand of over 80% in both laboratory and field conditions. It is also clarified that edamame's larger seed size leads to lower germination rates and slower emergence, although this is not correlated to total emergence. Moreover, environmental factors, pathogens and temperature, impact emergence. The study highlights that current edamame genotypes are commonly affected by soilborne pathogens, including Rhizoctonia solani, Athelia rolfsii, and Pythium irregulare, leading to seed rot and seedling damping off. However, the research has successfully identified partially resistant varieties characterized by significantly low disease indexes (p<0.05). Furthermore, the optimal temperature range for edamame seedling emergence (25-32°C) was found to be lower than that of other types of soybeans such as grain-type soybeans (29-36°C). This research provides a scientific foundation to improve edamame production practices. / Doctor of Philosophy / Vegetable soybean, also known as edamame, commonly consumed as a healthy snack, is steadily gaining popularity in the United States. However, there are significant challenges in achieving successful edamame plant growth from seeds. This research focuses on three primary objectives: first, understanding the underlying factors contributing to poor seedling emergence in edamame; second, identifying edamame genotypes with exceptional vigor and resistance to soil-borne diseases; and third, determining the ideal temperature conditions for optimal edamame seedling development. To accomplish these goals, a comprehensive study was conducted, encompassing various edamame varieties, including those developed by Virginia Tech and the University of Arkansas. The research identified some edamame genotypes that exhibited exceptional seed vigor, aging tolerance, and consistently achieved plant stands of over 80% under both laboratory and field conditions. Additionally, we also learned that bigger edamame seeds take longer time to grow, but the seed size does not affect the total emergence. Furthermore, we found that some diseases in the soil can hurt edamame seedlings, but we identified a few genotypes that are more resistant to these diseases. Lastly, in terms of temperature, we found that edamame seedlings grow the best between 25-32°C, which is slightly lower than other types of soybeans. Overall, this research helps farmers grow better edamame and brings more delicious and healthy food to our tables.

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O nitrogênio é um dos elementos mais limitantes no desenvolvimento de plantas. Vernonia herbacea (Vell.) Rusby, Asteraceae do cerrado, possui órgãos subterrâneos (rizóforos) que armazenam frutanos do tipo inulina. Estudos anteriores mostraram que o tratamento com solução nutritiva contendo 1,3 mmol L-1 NO3 - (Nlimitado) promoveu o acúmulo de frutanos nos rizóforos em detrimento do aumento de biomassa aérea e que o inverso ocorreu com plantas que receberam 10,7 mmol L-1 NO3 - (N-suficiente). Entretanto, não foram obtidas informações quanto às atividades das enzimas, em plantas sob esses tratamentos. Considerando a importância de estudos de nutrição mineral para a adequação de tratamentos de fertilização visando à produtividade de plantas de interesse econômico e em vista do teor elevado de frutanos em V. hebacea, este projeto teve como objetivos analisar o efeito do nitrogênio no crescimento e na alocação da biomassa, bem como no conteúdo e na composição de frutanos, nas atividades das enzimas de síntese (SST e FFT) e degradação (FEH e INV) de frutanos nos rizóforos e na atividade da redutase do nitrato (RN) e conteúdo de nitrato em folhas de V.herbacea. No presente trabalho, plantas de V. herbacea tratadas com baixo teor de nitrogênio (2,5 mmolL-1 de nitrato) apresentaram atividades de síntese (SST e FFT) superiores às tratadas com teor mais elevado de nitrogênio (11,9 mmol L-1 de nitrato), enquanto o inverso, ou seja, atividade elevada de despolimerização (FEH) ocorreu nas plantas que receberam 11,9 mmol L-1 de nitrato. O conteúdo de frutanos foi maior em plantas sob condições limitantes de nitrogênio, coerente com a maior atividade de síntese encontrada nestas plantas. Entretanto, maiores biomassas aérea e subterrânea foram encontradas nas plantas que receberam 2,5 mmolL-1 NO3 -, não sendo possível afirmar que baixos níveis de nitrato limitaram o seu crescimento. Dessa forma, para melhor compreensão do efeito do nitrato no crescimento, na alocação de biomassa e no metabolismo de frutanos em V. herbacea, foi conduzido um novo experimento que teve como objetivos analisar o efeito de diferentes concentrações de nitrato (0, 2,5, 5, 10 e 15 mM de KNO3) nos mesmos parâmetros analisados no experimento anterior em rizóforos e folhas de V. herbacea. Assim foi possível concluir que plantas tratadas com 10 mM apresentaram melhor eficiência no acúmulo total de biomassa e de frutanos nos rizóforos. Neste experimento, também foi demonstrado que plantas de V. herbacea, além dos frutanos, acumulam quantidades elevadas de nitrato nos rizóforos, mas assimilam preferencialmente esse mineral nas folhas. Uma vez que as plantas apresentaram maior massa seca aérea e subterrânea quando receberam soluções nutritivas enriquecidas com 10 mM de nitrato, foi realizado outro experimento para verificar a melhor fonte de nitrogênio no cultivo dessa espécie. As plantas foram submetidas ao cultivo com nitrato (KNO3), amônio ((NH4)2SO4) e a mistura de nitrato e amônio(NH4NO3), ambas na concentração de 10 mM, sendo possível verificar que esta espécie não apresentou preferência pela fonte nitrogenada, e sugerindo que o cultivo pode ser realizado em qualquer uma das fontes nitrogenadas estudadas. / Nitrogen is the most limiting element to plant development. Vernonia herbacea (Vell.) Rusby, Asteracea from the cerrado, bears underground organs (rhizophores) which accumulate inulin-type fructans. Previous studies showed that nutrient solution containing 1.3 mmol L-1 NO3 - (N-Limited treatment) promoted fructan accumulation in rhizophores and decrease of aerial biomass, while the opposite occurred in plants treated with nutrient solution containing 10.7 mmol L-1 NO3 - (N-sufficient treatment). However, as the activities of fructan metabolizing enzymes were not measured in these plants, new experiments were designed with this purpose. Thus, considering the importance of studies on mineral nutrition for the adjustment of the fertilization treatment, aiming at high contents of fructan and increase in plant productivity, the aim of this project was to analyse the effect of nitrogen on growth and biomass allocation, on fructan content and composition, on the activity of enzymes involved in fructan metabolism (SST, FFT, FEH and INV) in rhizophores, as well as on the activity of nitrate reductase (NR) and nitrogen content in leaves and rhizophores of V. herbacea. In the present work, plants treated with a low nitrogen concentration (2.5 mmol L-1 NO3 -) presented higher fructan biossynthetic activities than those treated with higher nitrogen concentration (11.9 mmol L-1 NO3 -). Oppositely, a higher mobilization activity occurred under high nitrogen concentration. Fructan content was higher in plants under low nitrogen concentration, in accordance with the higher biosynthetic activity in this treatment. However, higher aerial and underground biomass were detected in the 2.5 mmol L-1 NO3 - plants, indicating that growth was not limited under low levels of nitrate. Therefore, in order to improve the understanding of the effect of nitrate on growth, biomass allocation and fructan metabolism in V. herbacea, a new experiment was performed in which different concentrations of nitrate concentration (0, 2.5, 5.0, 10.0, 15.0 mM) were supplied in the same conditions mentioned above. The results showed that 10 mM nitrate was the most efficient concentration for total plant biomass and fructan accumulation in the rhizophore. It was also shown that, besides fructan, nitrate is accumulated in the rhizophores, but is preferably assimilated in leaves, where RN activity is higher. Considering results obtained with 10 mM nitrate, a third experiment was done in order to compare the effect of different nitrogen sources on growth of V. herbacea. The plants were treated with nutrient solutions containing ammoniun ((NH4)2SO4), nitrate(KNO3) and a mixture of nitrate and ammoniun (NH4NO3), both at a final concentration of 10 mM. No preference for the nitrogen source was observed when growth parameters were analysed. Therefore, the results suggest that plants of V. herbacea can be cultivated under any of the nitrogen sources used in this study.

A produção de mudas de caramboleira é um dos fatores limitantes à expansão comercial da cultura, devido ao tempo que estas levam para serem formadas e iniciarem a produção. Esta pesquisa teve como objetivo estudar os processos mais adequados para aumentar a eficiência da propagação por estaquia em caramboleira, utilizando-se diferentes tipos de estacas, técnicas de estiolamento e ferimento na base combinadas ao uso de reguladores de crescimento (AIB), e também estudar a estrutura anatômica e histológica dos diferentes tipos de estacas com relação à formação de raízes adventícias. O trabalho foi realizado com a instalação e condução de 3 (três) experimentos. Nos dois primeiros experimentos (I e II) foram testadas técnicas para maximizar a propagação por estacas da caramboleira. Foram utilizadas estacas da variedade Malásia, padronizadas com um par de folhas inteiras, com 12 (doze) cm de comprimento e 3 (três) gemas. O delineamento estatístico utilizado foi o inteiramente casualizado, em arranjo fatorial 3 x 4, onde os fatores estudados foram técnicas aplicadas nas estacas (estiolamento, ferimento na base e controle) e diferentes concentrações de AIB (0, 3000, 6000 e 9000 mg L-1) para estacas lenhosas (experimento I) e (0, 2000, 4000 e 6000 mg L-1) para estacas herbáceas (experimento II). As estacas foram mantidas em câmara de nebulização intermitente e após 75 dias, avaliaram-se as porcentagens de enraizamento, sobrevivência, formação de calos e número de raízes por estaca. Concluiu-se, para os dois experimentos, que as técnicas de estiolamento e ferimento na base da estaca foram prejudiciais à formação de raízes adventícias e a aplicação de AIB não mostrou diferença significativa para o enraizamento dos dois tipos de estacas estudados. No terceiro experimento foram feitos estudos anatômicos e histológicos que envolvem o processo de formação de raízes nas estacas. Estacas herbáceas, semilenhosas e lenhosas tratadas por imersão rápida em 0 e 3000 mg L-1 de ácido indolbutírico (AIB) foram mantidas em câmara de nebulização sob condições controladas por até 70 dias. Periodicamente as estacas foram cortadas, fixadas, desidratadas e preparadas para os cortes histológicos seriados e análise por microscopia óptica. Como conclusão, verificou-se que os diferentes tipos de estacas caulinares de caramboleira apresentaram estruturas anatômicas e histológicas distintas e a formação endógena de primórdios de raízes em estacas herbáceas ocorreu a partir do câmbio vascular. / The star fruit seedling production is one of the limiting factors to the commercial expansion of this culture, due to the time that they take to be formed and begin the production. The aim of this paper is to study the most adapted processes to increase the efficiency of stem propagation for star fruit using different types of cuttings, etiolating techniques and wound in the base combined to the use of growth regulators (IBA), and also to study the anatomical and histological structure of the different types of cuttings with related to the formation of adventitious roots. The work was accomplished with the installation and conduction of 3 (three) experiments. In the first two experiments (I and II) techniques were tested in order to improve the propagation by cuttings of the star fruit. Cuttings of the variety Malaysia were used and standardized with a pair of whole leaves, with 12 (twelve) cm of length and 3 (three) gems. The statistical design used was entirely randomized in arrangement to factorial 3 x 4, where the studied factors were the techniques applied in the cuttings (etiolating, wound in the base and control) and different concentrations of IBA (0, 3000, 6000 and 9000 mg L-1) for hardwood cuttings (experiment I) and (0, 2000, 4000 and 6000 mg L-1) for herbaceous cuttings (experiment II). The cuttings were maintained in chamber of intermittent mist and after 75 days, the percentages of root formation, survival, formation of calluses and number of roots per cuttings were evaluated. It is concluded for both experiments, that the etiolating techniques and wound in the base of the cuttings were harmful to the formation of adventitious roots and the application of IBA did not show significant difference for root formation of both types of cuttings studied. The third experiment carried out anatomical and histological studies that involve the process of formation of roots in the cuttings. Herbaceous, softwood and hardwood cuttings treated in fast immersion at 0 and 3000 mg L-1 of indolbutyric acid (IBA) were maintained in mist chamber under controlled conditions for up to 70 days. Periodically the cuttings were cut, fastened, dehydrated and prepared for the serial histological cuts and analysis through optical microscopy. As conclusion, it was verified that the herbaceous, softwood and hardwood cuttings of star fruit present different anatomical and histological structures and the endogenous formation of roots primordium in herbaceous cuttings occurred from the cambium.

A produção de mudas de caramboleira é um dos fatores limitantes à expansão comercial da cultura, devido ao tempo que estas levam para serem formadas e iniciarem a produção. Esta pesquisa teve como objetivo estudar os processos mais adequados para aumentar a eficiência da propagação por estaquia em caramboleira, utilizando-se diferentes tipos de estacas, técnicas de estiolamento e ferimento na base combinadas ao uso de reguladores de crescimento (AIB), e também estudar a estrutura anatômica e histológica dos diferentes tipos de estacas com relação à formação de raízes adventícias. O trabalho foi realizado com a instalação e condução de 3 (três) experimentos. Nos dois primeiros experimentos (I e II) foram testadas técnicas para maximizar a propagação por estacas da caramboleira. Foram utilizadas estacas da variedade Malásia, padronizadas com um par de folhas inteiras, com 12 (doze) cm de comprimento e 3 (três) gemas. O delineamento estatístico utilizado foi o inteiramente casualizado, em arranjo fatorial 3 x 4, onde os fatores estudados foram técnicas aplicadas nas estacas (estiolamento, ferimento na base e controle) e diferentes concentrações de AIB (0, 3000, 6000 e 9000 mg L-1) para estacas lenhosas (experimento I) e (0, 2000, 4000 e 6000 mg L-1) para estacas herbáceas (experimento II). As estacas foram mantidas em câmara de nebulização intermitente e após 75 dias, avaliaram-se as porcentagens de enraizamento, sobrevivência, formação de calos e número de raízes por estaca. Concluiu-se, para os dois experimentos, que as técnicas de estiolamento e ferimento na base da estaca foram prejudiciais à formação de raízes adventícias e a aplicação de AIB não mostrou diferença significativa para o enraizamento dos dois tipos de estacas estudados. No terceiro experimento foram feitos estudos anatômicos e histológicos que envolvem o processo de formação de raízes nas estacas. Estacas herbáceas, semilenhosas e lenhosas tratadas por imersão rápida em 0 e 3000 mg L-1 de ácido indolbutírico (AIB) foram mantidas em câmara de nebulização sob condições controladas por até 70 dias. Periodicamente as estacas foram cortadas, fixadas, desidratadas e preparadas para os cortes histológicos seriados e análise por microscopia óptica. Como conclusão, verificou-se que os diferentes tipos de estacas caulinares de caramboleira apresentaram estruturas anatômicas e histológicas distintas e a formação endógena de primórdios de raízes em estacas herbáceas ocorreu a partir do câmbio vascular. / The star fruit seedling production is one of the limiting factors to the commercial expansion of this culture, due to the time that they take to be formed and begin the production. The aim of this paper is to study the most adapted processes to increase the efficiency of stem propagation for star fruit using different types of cuttings, etiolating techniques and wound in the base combined to the use of growth regulators (IBA), and also to study the anatomical and histological structure of the different types of cuttings with related to the formation of adventitious roots. The work was accomplished with the installation and conduction of 3 (three) experiments. In the first two experiments (I and II) techniques were tested in order to improve the propagation by cuttings of the star fruit. Cuttings of the variety Malaysia were used and standardized with a pair of whole leaves, with 12 (twelve) cm of length and 3 (three) gems. The statistical design used was entirely randomized in arrangement to factorial 3 x 4, where the studied factors were the techniques applied in the cuttings (etiolating, wound in the base and control) and different concentrations of IBA (0, 3000, 6000 and 9000 mg L-1) for hardwood cuttings (experiment I) and (0, 2000, 4000 and 6000 mg L-1) for herbaceous cuttings (experiment II). The cuttings were maintained in chamber of intermittent mist and after 75 days, the percentages of root formation, survival, formation of calluses and number of roots per cuttings were evaluated. It is concluded for both experiments, that the etiolating techniques and wound in the base of the cuttings were harmful to the formation of adventitious roots and the application of IBA did not show significant difference for root formation of both types of cuttings studied. The third experiment carried out anatomical and histological studies that involve the process of formation of roots in the cuttings. Herbaceous, softwood and hardwood cuttings treated in fast immersion at 0 and 3000 mg L-1 of indolbutyric acid (IBA) were maintained in mist chamber under controlled conditions for up to 70 days. Periodically the cuttings were cut, fastened, dehydrated and prepared for the serial histological cuts and analysis through optical microscopy. As conclusion, it was verified that the herbaceous, softwood and hardwood cuttings of star fruit present different anatomical and histological structures and the endogenous formation of roots primordium in herbaceous cuttings occurred from the cambium.

O nitrogênio é um dos elementos mais limitantes no desenvolvimento de plantas. Vernonia herbacea (Vell.) Rusby, Asteraceae do cerrado, possui órgãos subterrâneos (rizóforos) que armazenam frutanos do tipo inulina. Estudos anteriores mostraram que o tratamento com solução nutritiva contendo 1,3 mmol L-1 NO3 - (Nlimitado) promoveu o acúmulo de frutanos nos rizóforos em detrimento do aumento de biomassa aérea e que o inverso ocorreu com plantas que receberam 10,7 mmol L-1 NO3 - (N-suficiente). Entretanto, não foram obtidas informações quanto às atividades das enzimas, em plantas sob esses tratamentos. Considerando a importância de estudos de nutrição mineral para a adequação de tratamentos de fertilização visando à produtividade de plantas de interesse econômico e em vista do teor elevado de frutanos em V. hebacea, este projeto teve como objetivos analisar o efeito do nitrogênio no crescimento e na alocação da biomassa, bem como no conteúdo e na composição de frutanos, nas atividades das enzimas de síntese (SST e FFT) e degradação (FEH e INV) de frutanos nos rizóforos e na atividade da redutase do nitrato (RN) e conteúdo de nitrato em folhas de V.herbacea. No presente trabalho, plantas de V. herbacea tratadas com baixo teor de nitrogênio (2,5 mmolL-1 de nitrato) apresentaram atividades de síntese (SST e FFT) superiores às tratadas com teor mais elevado de nitrogênio (11,9 mmol L-1 de nitrato), enquanto o inverso, ou seja, atividade elevada de despolimerização (FEH) ocorreu nas plantas que receberam 11,9 mmol L-1 de nitrato. O conteúdo de frutanos foi maior em plantas sob condições limitantes de nitrogênio, coerente com a maior atividade de síntese encontrada nestas plantas. Entretanto, maiores biomassas aérea e subterrânea foram encontradas nas plantas que receberam 2,5 mmolL-1 NO3 -, não sendo possível afirmar que baixos níveis de nitrato limitaram o seu crescimento. Dessa forma, para melhor compreensão do efeito do nitrato no crescimento, na alocação de biomassa e no metabolismo de frutanos em V. herbacea, foi conduzido um novo experimento que teve como objetivos analisar o efeito de diferentes concentrações de nitrato (0, 2,5, 5, 10 e 15 mM de KNO3) nos mesmos parâmetros analisados no experimento anterior em rizóforos e folhas de V. herbacea. Assim foi possível concluir que plantas tratadas com 10 mM apresentaram melhor eficiência no acúmulo total de biomassa e de frutanos nos rizóforos. Neste experimento, também foi demonstrado que plantas de V. herbacea, além dos frutanos, acumulam quantidades elevadas de nitrato nos rizóforos, mas assimilam preferencialmente esse mineral nas folhas. Uma vez que as plantas apresentaram maior massa seca aérea e subterrânea quando receberam soluções nutritivas enriquecidas com 10 mM de nitrato, foi realizado outro experimento para verificar a melhor fonte de nitrogênio no cultivo dessa espécie. As plantas foram submetidas ao cultivo com nitrato (KNO3), amônio ((NH4)2SO4) e a mistura de nitrato e amônio(NH4NO3), ambas na concentração de 10 mM, sendo possível verificar que esta espécie não apresentou preferência pela fonte nitrogenada, e sugerindo que o cultivo pode ser realizado em qualquer uma das fontes nitrogenadas estudadas. / Nitrogen is the most limiting element to plant development. Vernonia herbacea (Vell.) Rusby, Asteracea from the cerrado, bears underground organs (rhizophores) which accumulate inulin-type fructans. Previous studies showed that nutrient solution containing 1.3 mmol L-1 NO3 - (N-Limited treatment) promoted fructan accumulation in rhizophores and decrease of aerial biomass, while the opposite occurred in plants treated with nutrient solution containing 10.7 mmol L-1 NO3 - (N-sufficient treatment). However, as the activities of fructan metabolizing enzymes were not measured in these plants, new experiments were designed with this purpose. Thus, considering the importance of studies on mineral nutrition for the adjustment of the fertilization treatment, aiming at high contents of fructan and increase in plant productivity, the aim of this project was to analyse the effect of nitrogen on growth and biomass allocation, on fructan content and composition, on the activity of enzymes involved in fructan metabolism (SST, FFT, FEH and INV) in rhizophores, as well as on the activity of nitrate reductase (NR) and nitrogen content in leaves and rhizophores of V. herbacea. In the present work, plants treated with a low nitrogen concentration (2.5 mmol L-1 NO3 -) presented higher fructan biossynthetic activities than those treated with higher nitrogen concentration (11.9 mmol L-1 NO3 -). Oppositely, a higher mobilization activity occurred under high nitrogen concentration. Fructan content was higher in plants under low nitrogen concentration, in accordance with the higher biosynthetic activity in this treatment. However, higher aerial and underground biomass were detected in the 2.5 mmol L-1 NO3 - plants, indicating that growth was not limited under low levels of nitrate. Therefore, in order to improve the understanding of the effect of nitrate on growth, biomass allocation and fructan metabolism in V. herbacea, a new experiment was performed in which different concentrations of nitrate concentration (0, 2.5, 5.0, 10.0, 15.0 mM) were supplied in the same conditions mentioned above. The results showed that 10 mM nitrate was the most efficient concentration for total plant biomass and fructan accumulation in the rhizophore. It was also shown that, besides fructan, nitrate is accumulated in the rhizophores, but is preferably assimilated in leaves, where RN activity is higher. Considering results obtained with 10 mM nitrate, a third experiment was done in order to compare the effect of different nitrogen sources on growth of V. herbacea. The plants were treated with nutrient solutions containing ammoniun ((NH4)2SO4), nitrate(KNO3) and a mixture of nitrate and ammoniun (NH4NO3), both at a final concentration of 10 mM. No preference for the nitrogen source was observed when growth parameters were analysed. Therefore, the results suggest that plants of V. herbacea can be cultivated under any of the nitrogen sources used in this study.

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