Orientadores: Marcos Silveira Buckeridge, Marilia Gaspar / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-09T03:07:16Z (GMT). No. of bitstreams: 1 Souza_AmandaPereirade_M.pdf: 752519 bytes, checksum: 0abdf68fd1d19b70a0af931741ccf052 (MD5) Previous issue date: 2007 / Resumo: Desde o início da Revolução Industrial as concentrações de CO2 atmosférico aumentaram em cerca de 30% e estimativas apontam que esta concentração poderá atingir aproximadamente 720 ppm até a metade deste século. Estudos sobre o efeito do alto CO2 no desenvolvimento de diversas espécies vegetais já foram realizados, porém poucos com espécies de gramíneas tropicais do tipo C4, como é o caso da cana-de-açúcar. Considerando a importância econômica da cana e seu potencial na obtenção de biocombustíveis é importante saber como esta cultura irá responder ao aumento previsto na concentração de CO2 atmosférico. Sendo assim, o objetivo deste trabalho foi estudar o efeito do aumento do CO2 atmosférico sobre o crescimento, desenvolvimento e metabolismo de carboidratos da cana-de-açúcar visando avaliar o potencial de seqüestro de carbono e o impacto das mudanças climáticas sobre a produtividade. Parâmetros fisiológicos, bioquímicos e moleculares foram analisados em plantas cultivadas em câmaras de topo aberto durante 50 semanas com atmosfera de CO2 ambiente (~370 ppm) e elevada (~720 ppm). Os principais resultados obtidos indicam incremento em altura, na taxa fotossintética e em biomassa de colmo e folhas das plantas cultivadas sob elevado CO2. Ao final das 50 semanas foi detectado no colmo das plantas crescidas em tais condições, um aumento no teor de sacarose, de fibras e no conteúdo de celulose. A análise do perfil de transcritos de folhas após 9 e 22 semanas de cultivo usando microarranjos revelou expressão diferencial de 37 genes, sendo que 14 foram reprimidos e 23 foram induzidos e correspondem principalmente a genes de fotossíntese e desenvolvimento. Nossos resultados indicam que a cultura da cana-de-açúcar tem capacidade para seqüestro de carbono e potencial para aumento na produtividade em condições de alta concentração de CO2 / Abstract: Since the beginning of the Industrial Revolution, the concentrations of CO2 in the atmosphere increased about 30% and the current forecasts point out that this concentration will reach approximately 720 ppm until the middle of this century. Studies about the effect of CO2 on the development of several plant species have been performed. However, few studies have been performed with tropical grass species having photosynthesis C4, as is the case of sugar cane. Due to the economic importance of sugar cane and its high potential to obtain biofuel, it is important to known how this crop will respond to the forecasted increase in the CO2 concentration in the atmosphere. Therefore, the goal of this work was to study the effects of increased CO2 concentration on growth, development and carbohydrate metabolism of sugar cane aiming the evaluation of the potential of this specie for carbon sequestration and the impact of the global climatic change on its productivity. Physiological, biochemical and molecular features of these plants have been analyzed during 50 weeks of growth in Open-Top-Chambers (OTCs) with ambient (~370 ppm) and elevated (~720 ppm) CO2 concentrations. After 50 weeks of growth under these conditions, we observed an increase of sucrose content, fiber an also in cellulose contents in stems of plants grown under elevated CO2. The microarray analysis of the transcriptome of leaves was obtained after 9 and 22 weeks and revealed differential expression of 37 genes. Fourteen genes were repressed and 23 induced by elevated CO2. The latter correspond mainly to the processes of photosynthesis and development. Our results indicate that the sugar cane crop has a high potential for carbon sequestration and increase of productivity under elevated CO2 concentrations / Mestrado / Biologia Celular / Mestre em Biologia Celular e Estrutural

There have been a number of support initiatives rendered to the small-scale sugarcane farmers in Mpumalanga but the sugarcane production there has remained low. This raised some questions on the efficient use of available resources and the fruitfulness of the Producer Development Initiatives (PDIs). Justification for further assistance to the small-scale farmers requires empirical evidence of efficient resource use. This study employed the stochastic frontier production function to calculate the technical, allocative and cost efficiency. This study provides insight into three issues: the levels of technical, economic and allocative efficiencies of small-scale sugarcane farmers; the relationship between efficiency level and various farm/farmer specific factors; and implications of policy and strategies for improving small-scale sugarcane production. The technical, allocative and economic efficiencies of small-scale sugarcane farming were estimated in order to identify the potential increase in production without incurring additional costs. The study used data obtained from a field survey covering 231 small-scale sugarcane farmers in the Nkomazi region for the 2009/2010. sugarcane production season. According to the stochastic frontier production function using the Cobb-Douglas model, labour, herbicides and fertilizer showed significant positive effects on sugarcane production. The results also indicated that the small-scale sugarcane farmers suffer from considerable lack technical, allocative and cost efficiency. The mean technical, allocative and cost efficiency estimates are 68.5%, 61.5% and 41.8% respectively. A Tobit regression was used to analyse the impact of the farm/farmer characteristics on efficiency. The impact analysis revealed that age, level of education and gender are significant determinants of technical efficiency. On the other hand, level of education, off-farm income, land size and experience are significant determinants of allocative efficiency. In so far as cost efficiency is concerned, the significant determinants are level of education, land size and experience in sugarcane farming. The findings of the study justify the need for improved agricultural partnerships between the sugar mills and the sugarcane farmers. An example of such collaboration would be if millers were to not only give credit to the farmers, but also give technical guidance to small producers in return for the delivery of a specific quantity and quality of cane at a stipulated time. The collective efforts of these farmers and millers, once harmoniously co-ordinated, can enhance production efficiency and economic prosperity. Also, appropriate policy formulation and implementation is an effective instrument to improvement in farm efficiency and productivity which promotes overall growth of the economy. Therefore, there is need for all stakeholders (both private and public sector) to make combined efforts to remove the bottlenecks that have constrained effective policy implementation in, and its accrued benefits to, South African agriculture. / Dissertation MSc (Agric)--University of Pretoria, 2013. / gm2014 / Agricultural Economics, Extension and Rural Development / unrestricted