Alterações nutricionais, fisiológicas e moleculares em clones de eucalipto submetidos à omissão e ao ressuprimento de N ou P

• Autor(a) principal: Fernandes, Loane Vaz
• Data de Publicação: 2013
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/1652
• topic: Nutrição florestal; Eficiência nutricional; Expressão gênica; Forest nutrition; Nutritional efficiency; Gene expression; CNPQ::CIENCIAS AGRARIAS::AGRONOMIA::CIENCIA DO SOLO

Bigger EN is attributed to a larger acquisition (EA) and/or greater use (EU) of the nutrients and processes intermediated by transporting proteins, that answer in a different way to the supply of nutrients. Beyond proteins, many routes are modified in function of the nutritional supply and in different speeds. Thus, modifications in the coloration, nutritional content and growth are slower than physiological modifications, that, in turn, are slower than molecular ones. These different speeds of modification, united with the genetic control of these routes, join the nutrition of plants to genetic improvement, and can subsidize the choice of more e nutritionally efficient genetic materials, as well as indicating nutritional biomarkers. The objective of this study was to evaluate growth modifications, nutritional, physiological variables (gaseous exchanges, fluorescence of the chlorophyll and the pigment content), activity of key enzymes and expression of candidate genes associated with bigger efficiency of N or P in eucalyptus. Seedling of four clones (386, I-144, I-042 and VM 01) of eucalyptus grew in nutritional solution for 60 days, when the treatments, consisting of the omission of N or P, were applied for 21 days, followed by the resupply of the same for 14 days and controls (always with complete nutritional solution). Weekly, the growth of the plants was evaluated. On weeks 1, 3, 4 e 5, samples of diagnostic leaves were collected (young leaves totally expanded) to analyze the total content of P and N, the activity of reductase nitrate enzymes (NR - EC 1.0.0.1) and glutamine synthetase (GS - EC 6.3.1.2), for the treatments of N, and acid fosfate (APase - EC 3.1.3.2) and ribonuclease (RNase - EC 3.1.4.22) for the treatments of P. In weeks 1, 3, 4 and 5, samples were also taken to determine the content of photosynthetic pigments. Reading of the chlorophyll was also realized with a chlorophyll meter. In week 3, period of the largest omission of N or P, samples were collected to determine the expression of genes, with PCR-RT (reaction of reverse transcriptase in a chain of polymerase in real time) GS2;1, Gln1;3, NR1 e TIP2;1 for N and RNS1 e PHO1;H1 for P. At the end of the resupply, the mass of the dry matter of the plants, the content of the nutrients and the nutritional efficiencies were calculate. The omission/resupply of N caused a smaller production of dry matter, increase of EU and decrease of the EA. For P, there was an increase of EU and fall of EA, even though only clone 386 had presented lesser growth, indicating bigger adaptation of the plants due to the lack of P. The omission led to the fall of levels of N and increase in the activity of all the enzymes and expression of all the genes, especially the GS2; 1 and GLn1; 3. The fall in the level of liquid photosynthesis (A), omitting N, can be explained by lesser levels of pigments and damages in the photochemical stage of the photosynthesis, by the oxidation of photosystem II (FSII), and the possible fall in the level of rubisco. There was a fall in the level of P in the first week of omission. In week 3, still under the omission, the level was equal to the controls, in virtue of the high internal cycling, proven by the increase of the activity of phosphohidrolases and expression of the genes (PHO1;H1 and RNS1). The fall of A can be explained by damages to the FSII because of the lesser level of inorganic P for the formation of ATP and NADPH, diminishing the level of electron transport (ETR) and, with this A. The enzyme with bigger relative activity, for N, was the GS in the I-144 clone (73,6 times), because of the increase of the expression of the GS2; 1. For P, the biggest increase (16,2 times) was observed for RNase enzyme, also for the I-144 clone and proven by the increase of the RNS1, showing transcriptional control of this gene. The resupply tended to reestablish the nutritional status, variable of the photosynthetic apparatus and enzymes related to N (NR and GS) of the plants, evidencing great resilience of the eucalyptus. This pattern happened again for P, with exception of the enzymes APase and RNase, whose activities still were relatively high in week 5. The resistance/resilience of the eucalyptus clones against the omission/resupply of N or P involves alterations in many variables, and those that presented greater potential such as biomarkers in eucalyptus are: the coefficient of photochemical dissipation (YII); level of transportation of electrons; activity of the enzyme GS; and expression of the genes GS2;1 and Gln1;3 as to the status of N; photosynthetic level; RNase enzyme and the gene RNS1 as to the status of P.