Conselho Nacional de Desenvolvimento Científico e Tecnológico / Maize is an important crop of cereals around the world and one of the most mathematical models used to simulate the growth and development of maize is the CSM-Ceres-Maize model. However, the use of this model for open pollination varieties (landraces and improved) was not found in the literature. The objectives of this dissertation were (a) Calibrate the CSM-Ceres-Maize model available on the DSSAT v4.5 platform (Decision Support System for Agrotechnology Transfer) for two landrace maize cultivars ('Cinquentinha' and 'Bico de Ouro ), an improved variety ('BRS Missões') and a modern hybrid ('AS 1573PRO') and (b) Apply the CSM-Ceres-Maize model in Rio Grande do Sul State to simulate the kernel yield of the four cultivars for the recommended period and compare the agronomic performance of the open pollinated varieties with the hybrid in the condition without water restriction. The calibration of the CSM-Ceres-Maize model on the DSSAT platform was performed using the trial and error approach, obtaining a total of 7 parameters calibrated with a field experiment conducted in Santa Maria, in the 2013/14 growing seasons (Sowing date: 11/04/2013). The test of the model was performed with independent data obtained from the field experiment in Santa Maria, RS, with sowings dates in 08/20/2013, 02/03/2014 and 08/15/2014, and also the model was run for 15 locations in Rio Grande do Sul State, with sowing date range in a 5-day time step to analyze the kernel yield between cultivars. The model was able to simulate the phenology and productivity of four cultivars, capturing the evolution of each one during your cycle. Also, it was possible to prove the stability of potential kernel yield of the landrace maize cultivars in comparison with the hybrid. / O milho é uma importante cultura de cereais ao redor do mundo e um dos modelos matemáticos mais usados para simular o crescimento e desenvolvimento desta cultura é o modelo CSM-Ceres-Maize. No entanto, o uso deste modelo para cultivares de polinização aberta (crioulas e melhoradas) não foi observado na literatura. Os objetivos desta dissertação foram (a) calibrar o modelo CSM-Ceres-Maize disponível na plataforma DSSAT v4.5 (Decision Support System for Agrotechnology Transfer) para duas cultivares crioulas de milho ( Cinquentinha e Bico de Ouro ), e duas melhoradas, uma variedade de polinização aberta ( BRS Missões ) e um híbrido simples ( AS 1573PRO ) e (b) aplicar o modelo CSM-Ceres-Maize no Rio Grande do Sul para simular a produtividade de grãos das quatro cultivares durante o período recomendado e comparar o desempenho agronômico das cultivares de polinização aberta com o híbrido na condição sem restrição hídrica. A calibração do modelo CSM-Ceres-Maize na plataforma DSSAT foi realizada através do método dos mínimos quadrados, obtendo-se um total de sete parâmetros calibrados com um experimento de campo realizado em Santa Maria, RS, no ano agrícola 2013/14 (Semeadura: 04/11/2013). O teste do modelo foi realizado com dados independentes obtidos através do experimento de campo em Santa Maria, RS, com semeaduras em 20/08/2013, 03/02/2014 e 15/08/2014 e, também o modelo foi rodado para 15 locais no Rio Grande do Sul, com data de semeadura variando em um passo de tempo de 5 dias para analisar a diferença de produtividade entre as cultivares. O modelo foi capaz de simular a fenologia e produtividade das quatro cultivares, captando a evolução de cada uma no decorrer do seu ciclo. Também, foi possível comprovar a estabilidade na produtividade potencial de grãos das cultivares crioulas em comparação com o híbrido.

Seeds are essential elements within agricultural production and food systems. However, seed systems face multiple issues, including processes of commercialisation, privatisation, and crop diversity loss, that require reconsidering current approaches to seeds and varieties. Seed initiatives hold a potential to contribute to alternative and desirable seed system configurations and outcomes. In this thesis, I analyse how existing seed initiatives increase their impact, drawing on the typology of amplification processes by Lam et al. (2020). Furthermore, due to the long-term occurrence of variety losses and the complexity of the processes involved, this thesis uses system dynamics concepts and diagramming tools to map the use of local varieties from the initiatives’ perceptions. Thereby, I attempt to operationalise amplification, depict local variety use, and combine the two approaches within the context of seed initiatives. I employ a case-study approach in Italy and conducted semi-structured interviews with members of six seed initiatives. Concrete actions for almost all the frameworks’ processes were found. Building stability, influencing values and mindsets, and strategically impacting higher institutional levels emerged as suitable ways to amplify and might indicate that initiatives prepare and potentially navigate change. Enhancing the initiatives’ impact range and speed benefitted from more nuance due to diverging notions on these processes. A qualitative systems diagram with social and ecological components maps causal structures that influence the use of local varieties, showing a potential for desirable dynamics. By indicating how amplifying actions relate to the system structure, I illustrate how the seed initiatives are influencing multiple system parts. Thus, the system maps revealed perceived system structure, which by itself might run the risk of portraying path dependency, while amplification relates to agency on how initiatives might influence the system.

Submitted by Sandra Pereira (srpereira@ufrrj.br) on 2016-08-09T12:24:30Z No. of bitstreams: 1 2011 - Carlos Alberto Bucher.pdf: 775464 bytes, checksum: 84e941a946068132678bc3f55c09561d (MD5) / Made available in DSpace on 2016-08-09T12:24:30Z (GMT). No. of bitstreams: 1 2011 - Carlos Alberto Bucher.pdf: 775464 bytes, checksum: 84e941a946068132678bc3f55c09561d (MD5) Previous issue date: 2011-02-23 / Funda??o Carlos Chagas Filho de Amparo ? Pesquisa do Estado do RJ - FAPERJ / Nitrogen is one of the nutrient elements most limiting for plant growth. Thus, increasing plant nitrogen usage efficiency (NUE) is an essential factor for sustainable agriculture, leading to an increased food production with less fertilizer input and less environment impact. NUE in plant involves the uptake and accumulation efficiency, and N use efficiency for grain production. Understanding the mechanisms regulating these processes is crucial for the improvement of NUE in crops. Therefore, is essential to comprehend plants response to different N regimes, mainly N limitation. The usage of plants or varieties with differences in nutrient use efficiency is another important factor to determine the main mechanisms involved in these processes. The objectives of this study were to evaluate N metabolism and expression of genes involved in N uptake and assimilitation of two rice varieties (Piau? and IAC-47), under different N supply conditions. The N metabolism was evaluated by quantification of nitrogen fractions in plant tissue and enzymatic activity, expression of genes that code for high and low affinity N transporters, and N assimilation enzymes. Two experiments were conducted: the first, to investigate the plants behavior when grown under high and low N supply; and the second to verify plants response to NO3 - resupply. The IAC-47 variety showed greatest mass accumulation in all treatments. When plants were grown for a long period under low N supply it was observed a higher nitrate (NO3 -) content in the tissue of Piau? variety, which is adapted to low fertility conditions, as well as a high activity of nitrate reductase and glutamine synthetase in the roots of these plants. When under high NO3 - supply for a long period, Piau? variety had higher NO3 - concentrations in roots and sheaths, but no differences were observed in enzymes activity. The nitrate transporters expression was higher in roots of Piau? plants under low supply of NO3 - when compared to Piau? plants under high N supply. Nitrate transporters expression in roots of IAC-47 plants showed a pattern opposite to the one observed for Piau? plants. When plants were resupplied with NO3 -, after a 72 hours period without N, there was a rapid increase, after 6 hours of resupply, in the expression of high affinity nitrate transporters genes (OsNRT2.1) and the plastidial glutamine synthetase (GS2) in the Piau? variety roots, and a higher expression of these in IAC-47 roots after a 24 hours of N resupply. The efficiency of Piau? variety is related to the differentiated control of N absorption and assimilation mechanisms, which allow bigger expression of high affinity nitrate transporters in tissue with high levels of soluble N, high N status, indicating that the control of nitrogen uptake system may be essential for the nitrogen usage efficient. / O nitrog?nio ? um dos elementos minerais que mais limita o desenvolvimento das plantas. Assim, aumentar a efici?ncia de uso de nitrog?nio (EUN) ? um fator ? essencial para uma agricultura sustent?vel, levando a um aumento da produ??o de alimentos com menor uso de insumos e menos impactos ao ambiente. A EUN envolve a efici?ncia de absor??o e ac?mulo e a efici?ncia de utiliza??o de N para produ??o. Compreender os mecanismos envolvidos nesses processos e como eles s?o controlados ? fundamental para a melhoria da EUN nas plantas cultivadas. Para isso, ? essencial entender a resposta e comportamento das plantas a diferentes regimes de N, principalmente ? limita??o de N. O uso de plantas ou variedades com diferen?as na EUN ? outro fator importante para verificar os principais mecanismos envolvidos. Este trabalho teve por objetivo desse trabalho foi verificar o metabolismo e a express?o de genes envolvidos na absor??o e assimila??o de nitrog?nio nas variedades de arroz Piau? e IAC-47 sob diferentes condi??es de disponibilidade desse nutriente. O metabolismo de N foi avaliado atrav?s da quantifica??o das fra??es nitrogenadas no tecido e atividade enzim?tica, a express?o de genes que codificam para transportadores de N de alta e baixa afinidade e enzimas de assimila??o de N. Foram realizados dois experimentos: o primeiro para verificar o comportamento das plantas quando cultivadas sob alto e baixo suprimento de N; e o segundo, para verificar as repostas ao ressuprimento de N. O ac?mulo de massa foi maior na variedade IAC-47 em todos os tratamentos. Quando as plantas foram cultivadas por um longo per?odo sob baixo suprimento de N foi observado maior teor de nitrato (NO3 -) no tecido da variedade Piau?, adaptada a condi??es de baixa fertilidade, assim como uma alta atividade da nitrato redutase e glutamina sintetase nas ra?zes dessas plantas. Sob alto suprimento de NO3 -, por um longo per?odo, a variedade Piau? apresentou maiores teores de NO3 - nas bainhas e ra?zes, mas n?o foram observas diferen?as na atividade de enzimas. A express?o dos transportadores de nitrato na variedade Piau? foi mais elevada nas ra?zes das plantas sob baixo suprimento de NO3 - quando comparado as plantas sob alto suprimento de N. Na variedade IAC-47 a express?o dos transportadores de NO3 - teve comportamento oposto ao observado para a Piau?. Quando as plantas receberam NO3 -, ap?s um per?odo de 72 horas sem N, houve um r?pido aumento, ap?s 6 horas do ressuprimento, na express?o do gene que codifica para o transportador de NO3 - de alta afinidade OsNRT2.1 e glutamina sintetase plastidial (GS2) nas ra?zes da variedade Piau?, e 24 horas ap?s o ressuprimento a express?o foi maior na variedade IAC-47. A efici?ncia da variedade Piau? esta relacionada ao controle diferenciado dos mecanismos de absor??o e assimila??o de N, que permite a maior express?o dos transportadores de nitrato de alta afinidade em tecido com altos teores de N sol?vel, alto status de N, indicando que o controle do sistema de absor??o de N pode ser essencial para a efici?ncia no uso de nitrog?nio.