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| Author(s): |
Cristina Aledi Felsemburgh
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | Piracicaba. |
| Institution: | Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC) |
| Defense date: | 2009-08-11 |
| Examining board members: |
Plinio Barbosa de Camargo;
Antonio Natal Gonçalves;
Denis Ubeda de Lima;
Jean Pierre Henry Balbaud Ometto;
Simone Aparecida Vieira
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| Advisor: | Plinio Barbosa de Camargo |
| Field of knowledge: | Biological Sciences - Ecology |
| Indexed in: | Banco de Dados Bibliográficos da USP-DEDALUS; Biblioteca Digital de Teses e Dissertações - USP |
| Location: | Universidade de São Paulo. Biblioteca da Escola Superior de Agricultura Luiz de Queiroz; t634.90913 e.1 95081; F324r |
| Abstract | |
Tropical forests hold large stores of carbon as biomass. They are characterized by large net primary productivity, however, it is not well understood how carbon budgets of tropical forests respond to the advance of climatic changes. Temperature is one of the agents related to the increase of carbon dioxide concentration in the atmosphere and ambient temperatures can contribute to alterations in assimilation or emission of CO2 in tropical forests. Temperature has been pointed as responsible for gas exchange rates in plants, affecting the photosynthesis and respiration. Thus, studies aimed at better understanding of physiological processes of plants, particularly those which involve carbon cycling, are important to generate information on the effects of the global changes in the trends of CO2 assimilation response in plants or in ecosystems. The objective of this work was to determine the photosynthesis processes and respiration responses as a function of leaf temperature of an individual and of the community in study. The study was carried out at the Tapajós National Forest (FLONA, 2º 51` S 54º 58` W) located in the south of Santarém municipality, at kms 67 and 83 of the Santarém- Cuiabá highway (BR-163). Five towers were used to support measurements in leaves in the forest canopy. An infra-red gas analyzer (IRGA, LI-6400 model) was utilized for quantification of leaf photosynthesis and respiration. For each observed leaf, a curve relating the photosynthesis response to the photosynthetically active radiation (PAR) was obtained together with four curves of photosynthesis response in relation to the internal CO2 concentration (Ci) in four groups of leaf temperatures (Tleaf). The response curves of PAR, Tleave and internal CO2 concentration (Ci) were obtained between 07h00 and 14h00. For the diurnal cycle it was quantified photosynthesis (A), stomatal conductance (gs), transpiration (E) and vapor pressure deficit of the leaf (VPDf), and measurements were carried out throughout one day between 10h00 and 18h00. The main optimum temperature of photosynthesis was 29.9 °C, and the community presented optimum CO2 net assimilation rate of 7.2 µmol.m-2.s-1. Leaf temperature values above 32.9 °C and 32.5 °C decreased the maximum capacity of electron transport and the maximum speed of carboxylation, respectively. The carboxylation efficiency starts to decreased at 31 °C. The internal CO2 concentration diminished 32.6% at 42 °C In the evaluation of the diurnal cycle, photosynthesis and stomatal conductance decreased significantly after 16h00 and 15h00 hours, respectively. An increase of 0.34 kPa in VPDf diminished transpiration in 64%. The stomatal conductance decreased with increase of leaf temperature and leaf respiration was positively related to the increase of leaf temperature. (AU) | |
| FAPESP's process: | 06/57010-4 - Primary liquid productivity in different phytophysiognomies in the Serra do Mar State Park, São Paulo |
| Grantee: | Cristina Aledi Felsemburgh |
| Support Opportunities: | Scholarships in Brazil - Doctorate |