Diffusion and assimilation of the CO2 in C4 plants (Saccharum spp. e Sorghum bicolor) its relationship with leaf nitrogen and water deficit

Author(s)

Naiara Célida dos Santos de Souza

• Document type: Doctoral Thesis
• Press: Piracicaba.
• Institution: Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC)
• Defense date: 2016-12-15

Examining board members

Victor Alexandre Vitorello; Gustavo Habermann; Lazaro Eustaquio Pereira Peres; Rafael Vasconcelos Ribeiro; Joaquim Albenisio Gomes da Silveira

• Advisor: Victor Alexandre Vitorello

Abstract

Increased demand for food production and the possibility of global climate change has promoted renewed interest in photosynthesis research. It is expected that with the photosynthetic improving the crop productivity increase. For this, besides of the use of biotechnological practices, further studies are needed about intrinsic limitations of the photosynthetic process that can contribute to the identification of targets for genetic engineering. In this context, this thesis discusses specific questions about photosynthesis regulation C4 by nitrogen nutrition, water deficit and the interaction of these two factors. In the chapter I, it was developed a study of the effects of nitrogen nutrition in the internal diffusion of CO2. It was observed that the leaf nitrogen (N) is essential for the internal CO2 conductance (Δ 18O-gm). A lower leaf N induces initial reductions in Δ18O-gm by lower activity of the carboxylation enzymes. With N leaf reduction in older leaves anatomy changes began to contribute to the regulation of Δ18 O-gm. In the chapter II, the genotypic variation of sugarcane to photosynthetic parameters and leaf nitrogen was explored, involving the photosynthetic nitrogen use efficiency (PNUE) and heritability analysis. The variability of the genetic material is explained mainly by gas exchange parameters that contributed to the grouping of materials into three groups. From this, it is possible examine the differences between the materials in response to nitrogen nutrition. Furthermore, gas exchange parameters such as CO2 assimilation rate and stomatal conductance along with PNUE showed high heritability in the narrow sense. Finally, the chapter III investigated the regulation of CO2 assimilation metabolism in response to water deficit sugarcane leaves and how nitrogen metabolism is involved in this process. Different factors involved in the negative regulation of photosynthesis were identified. Interestingly, changes in nitrogen components only contributed to metabolic inhibition in severe stress. Additionally it noted that overcoming metabolic inhibition during rehydration is faster when the cultivar presents slower decreases in N metabolism during water deficit, associated with less damage to the photosynthetic capacity. (AU)

• FAPESP's process: 13/07665-8 - CHANGES IN LEAF NITROGEN METABOLISM OF SUGARCANE PLANTS EXPOSED TO WATER DEFICIT AND ITS RELATION TO CO2 ASSIMILATION
• Grantee: Naiara Célida dos Santos de Souza
• Support Opportunities: Scholarships in Brazil - Doctorate