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Sugars have a profound impact on plant biology, acting as structural components, signalling molecules, and sources of energy. As such, the availability of sugars has important implications for plant growth and development. Sugar levels rise and fall as part of a daily cycle, while cues from other environmental stimuli are also in flux. As sessile organisms in an ever-changing environment, plants must integrate signals from multiple pathways in order to promote the appropriate developmental responses. To uncover pathways that interact with sugars during seedling development, a chemical screen was performed in search of compounds that modify responses to sucrose. This screen identified an interaction between the folate inhibitor sulfamethoxazole (SMX) and sucrose that resulted in changes to auxin signalling and distribution. Synergy between sucrose and SMX was used to explore the effect of metabolic cues on auxin signalling during hypocotyl elongation. A second line of investigation explored whether sucrose and folates influence root meristem activity. Sucrose induced hormone signalling pathways that promote cell division and differentiation. Treatment with SMX perturbed the effect of sucrose on hormone networks that mediate growth, and resulted in a loss of meristem integrity. This study highlights the influence of metabolism on hormone signalling at the root apex, and its role in maintaining balance of a complex signalling network that drives root growth. These studies characterise an interaction between metabolic pathways that is integrated with hormone signalling during plant development. Taken together, they highlight a mechanism through which plant growth might be regulated by metabolism.

Sugars have a profound impact on plant biology, acting as structural components, signalling molecules, and sources of energy. As such, the availability of sugars has important implications for plant growth and development. Sugar levels rise and fall as part of a daily cycle, while cues from other environmental stimuli are also in flux. As sessile organisms in an ever-changing environment, plants must integrate signals from multiple pathways in order to promote the appropriate developmental responses. To uncover pathways that interact with sugars during seedling development, a chemical screen was performed in search of compounds that modify responses to sucrose. This screen identified an interaction between the folate inhibitor sulfamethoxazole (SMX) and sucrose that resulted in changes to auxin signalling and distribution. Synergy between sucrose and SMX was used to explore the effect of metabolic cues on auxin signalling during hypocotyl elongation. A second line of investigation explored whether sucrose and folates influence root meristem activity. Sucrose induced hormone signalling pathways that promote cell division and differentiation. Treatment with SMX perturbed the effect of sucrose on hormone networks that mediate growth, and resulted in a loss of meristem integrity. This study highlights the influence of metabolism on hormone signalling at the root apex, and its role in maintaining balance of a complex signalling network that drives root growth. These studies characterise an interaction between metabolic pathways that is integrated with hormone signalling during plant development. Taken together, they highlight a mechanism through which plant growth might be regulated by metabolism.

Thesis (M.S.)--California Polytechnic State University, 2009. / Mode of access: Internet. Title from PDF title page; viewed on August 6, 2009. Major professor: Dr. Lauren Garner. "Presented to the faculty of California Polytechnic State University, San Luis Obispo." "In partial fulfillment of the requirements for the degree [of] Master of Science in Agriculture with specialization in Crop Science." "June 2009." Includes bibliographical references (p. 37-49).

Thesis (Ph.D.) - University of Queensland, 2005. / Includes bibliography.

Thesis (Ph. D.)--University of Texas at Austin, 2004. / Supervisor: Stanley J. Roux. Vita. Includes bibliographical references.

No description available.

The regulation of morphogenesis by exogenous auxin / cytokinin ratio was investigated in thirty ornamental species and cultivars of Rosaceae and Ericaceae. Shoot explants were cultured in vitro on nutrient medium containing 0 to 20 mg 1-1 indole-butyric acid (IBA), naphthalene-acetic acid (NAA), 2,4-dichlorophenoxyacetic acid (2,4-D), benzyladenine (BA), isopentenyladenine (2iP), or kinetin. Shoot, root and callus formation were recorded after four-week incubation periods. Exogenous cytokinin was necessary for shoot formation, and exogenous auxin for root formation, while callus formation occurred in the presence of exogenous auxin or cytokinin. BA induced the formation of many short shoots whereas 2iP induced fewer longer shoots probably due to 2iP oxidation and BA-stimulated ethene synthesis. Four different callus types formed in response to growth regulator applied, growth regulator concentration, light and temperature. Auxin-induced callus and root formation was promoted by darkness whereas cytokinin- promoted callus formation was promoted by light. Elimination of potassium from the medium increased root formation but decreased shoot and callus formation. Low medium pH promoted root and callus formation while a higher pH stimulated shoot formation. The presence of axillary buds and the shoot apex promoted root and callus formation but inhibited shoot formation. Cytokinin-enhanced respiration rate and ethene synthesis was related to caulogenesis, but auxin- promoted respiration rate and ethene synthesis was not correlated with rhizogenesis. Ethephon and ethene promoted simultaneous shoot and root formation but ethene was shown to be unlikely to act as an intermediate in all auxin- and cytokinin-induced differentiation. Repeated subculture of shoots resulted in an initial rise followed by a decline in caulogenesis, a decline in root formation and an increase in callus formation (apparently irreversible decline). Shoot length and leaf size decreased with repeated subculture but increased after auxin, gibberellin, or decreased illumination treatment. Auxin and cytokinin treatment could not override species and cultivar variation in morphogenesis.

Orientador: Iraê Amaral Guerrini / Coorientador: Léo Zimback / Banca: Dirceu Maximino Fernandes / Banca: Magali Ribeiro da Silva / Banca: Clarice Backes / Resumo: A cultura do eucalipto é de ampla distribuição mundial bem como no território nacional. A possibilidade de obtenção de genótipos superiores principalmente relacionado a questão nutricional, são os objetivos dos profissionais de melhoramento florestal. O uso de herbicidas proporcionou ganhos de produtividades para as culturas agrícolas, porém sua utilização direta e benéfica a uma espécie em questão, conhecido recentemente pelo termo hormese, pode ser associado a aplicação de reguladores vegetais. O herbicida 2,4-D possui este efeito e a utilização em uma cultura dicotiledônea e florestal, como a de Eucalyptus grandis, é o objetivo do presente trabalho, bem como mensurar parâmetros genéticos, utilizados em programas de melhoramento para a produção final de clones e na manutenção da variabilidade em futuros cruzamentos. O delineamento do experimento foram blocos ao acaso com 3 blocos de 20 progênies. As análises estatísticas foram teste t de Student, análise agrupamentos, análise de componentes principais scores e ranqueamento.Os nutrientes analisados foram: N, P, K, Ca, Mg, S, B, Cu, Fe, Mn e Zn. Os resultados demonstraram que houveram diferenças significativas nos nutrientes abordados, macro e micronutrientes bem como no principal caractere produtivo, matéria seca. P, B, Mn e K foram os nutrientes melhores correlacionados com matéria seca. Pela análise de variância de matéria seca as progênies 1, 18 e 17 foram as melhores, com herdabilidade de 0,89. As progênies 10, 15, 20 e ... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The eucalyptus crop is widely distributed worldwide as well as in the national territory. The possibility of obtaining superior genotypes mainly related to nutritional question, are the objectives of professionals of forest improvement. The herbicides uses provided yield gains for agricultural crops, but their direct and beneficial use to a species in question, recently known by the term hormesis, may be associated with the application of growth regulators. The 2,4-D herbicide has this effect and has use in a dicotyledonous and forest crops, like Eucalyptus grandis, the aim of the present work is to measure genetic parameters, used in breeding programs to the final clones productions and the maintenance of variability in the future crossings. Statistical tests used were Student's t test, cluster analysis, principal component analysis scores and rank. The analyzed nutrients were: N, P, K, Ca, Mg, S, B, Cu, Fe, Mn and Zn. The results showed that there were significant differences between macro and micronutrients as well as in the main productive character, dry matter. P, B, Mn and K were the best nutrients correlated with dry matter. By the dry matter variance analysis progenies 1, 18 and 17 were the best, with a heritability of 0.89. Progenies 10, 15, 20 and two other groups would act to maintain future variability at future crosses. The best genetic correlations between dry matter and nutrients involved phosphorus, boron, manganese and potassium, in this respective order. Using the index ... / Doutor

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