Enriquecimento e alocação de 13C em plantas de eucalipto

• Autor(a) principal: Machado, Daniel Nolasco
• Data de Publicação: 2009
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/5419
• topic: Eucalipto; Enriquecimento com 13C; Matéria orgânica do solo; Eucalypt; Enrichment with 13C; Soil organic matter; CNPQ::CIENCIAS AGRARIAS::AGRONOMIA::CIENCIA DO SOLO

In the last decades the use of stable isotopes has gained importance in several research areas, such as metabolites flow and pathways, the effects of biotic and abiotic stresses on plants, and in studies of soil organic matter (SOM). Studies on the alterations and dynamics of SOM using variation in 13C natural abundance require changes in the C isotopic composition, which not always is observed. One alternative is to label plant materials with 13C, via 13CO2, so that the C isotope ratio is different from that of native soil organic matter. Thus, the objective of the current study was to investigate how homogeneous was the labeling as well the allocation to different plant parts of applied 13C. Labeling was carried out with three 4-month old eucalypt plants grown in nutrient solution using a pulse technique. Plants were exposed to an atmosphere enriched with 13CO2 using 448 dm3 -glass chambers, under controlled temperature. The CO2 concentration and the 13C/12C ratio were monitored through off-line gas samples analysis in an isotope ratio mass spectrometer (IRMS) along the pulse-labeling period (126 days, using three pulses per week). After the labeling period the plants were separated in leaves (mature-source leaves and young-drain leaves), branches, bark, stem, and roots, which were then analyzed in an IRMS. The results were expressed in parts per mill ( ) relative to the Pee-Dee Belemnite standard (δ13CPDB). The δ13CPDB found were: 828.07 for young leaves, 645.7 for mature leaves, 672.5 for branches, 691.9 for bark, 632.02 for stem, and 536.6 for roots. The 13C allocation and enrichment pattern among plant parts was homogeneous (statistically equal), although variations in δ13CPDB of 292 % between plant parts were observed. The eucalypt plants maintained a high CO2 absorption, thus photosynthetic rates, even under high CO2 concentrations (180.4 mmol L-1 7.934 ppmv) that are well above the normal atmospheric CO2 concentration (8.64 mmol L-1 380 ppmv). The recently fixed 13C was proportionally less respired at night in comparison to the 12C.