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Ecophysiological characterization of two species of genus Cordia (Boraginaceae) grown under different light intensities and exposed to severe light stress

Grant number: 10/07014-9
Support type:Scholarships in Brazil - Scientific Initiation
Effective date (Start): July 01, 2010
Effective date (End): December 31, 2010
Field of knowledge:Biological Sciences - Botany
Principal Investigator:Carlos Alberto Martinez y Huaman
Grantee:Matheus Enrique Bianconi
Home Institution: Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto (FFCLRP). Universidade de São Paulo (USP). Ribeirão Preto , SP, Brazil


Given the richness of plant species in Brazil, knowledge of the physiology of native plants under stressful environmental conditions is a major step towards diversification of reforestation on the recovery of degraded areas and the suit to environmental laws. When subjected to extreme environmental conditions, such as water shortage or excess of sun radiation, plants have altered their physiology and may suffer local injuries or until the plant death. Such damage is mainly induced by oxidative stress caused by the accumulation and action of reactive oxygen species (ROS), free radicals that can cause the destruction of proteins and nucleic acids, lipid peroxidation of membranes and hence cell death. In this study, seedlings of two congeneric species of Boraginaceae, a pioneer - Cordia trichotoma (Vell.) Arrab. ex Steud. - And a non-pioneer - Cordia superba Cham. - Will be acclimated under three light conditions: 100% of radiation (full sunlight) and interference of 50% and 75% in the radiation (shadow). Plants grown under shade will later be transferred to full sunlight in order to induce severe light stress, mimicking the opening of a natural clearing or deforestation. Will be determined gas exchange parameters, pigment concentration, chlorophyll fluorescence and growth. Oxidative stress will be assessed based on the quantification of the activity of superoxide dismutase (SOD) and in situ detection of free radicals and cell death. The physiological and biochemical analysis will be conducted before, during and after the induction of severe light stress. The data generated will determine the best conditions for the development of such species and which are the physiological differences between these phylogenetically related species and evaluate the behavior of plants when subjected to light stress caused by treefall gaps or deforestation. The results will be analyzed based on the hypothesis that pioneer species have a set of biochemical and physiological responses consistent with greater tolerance to clearing areas compared to non-pioneer species.