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ESCOLA POLITÉCNICA DA UNIVERSIDADE DE SÃO PAULO AGRICULTURAL AUTOMATION LABORATORY INSTITUTO DE BOTÂNICA PLANT PHYSIOLOGY AND BIOCHEMISTRY SECTION SEASONAL CHANGES OF ECOPHYSIOLOGICAL RESPONSES OF Hymenaea courbaril L. Madeleine Barriga Puente de la Vega Antonio Mauro Saraiva Marcos Silveira Buckeridge Henrique Pessoa dos Santos Isis Santos Costa
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2 TOPICS Motivation Objectives Experimental part Results Conclusions
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3 MOTIVATION Production of scientific data of native plants Role of tropical forests in the global carbon balance In this work CO 2 assimilation was monitored for one year in Hymenaea courbaril (jatobá) Photosynthesis process is a key
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4 OBJECTIVES Monitoring CO 2 assimilation and environmental variables for one year in young plants of Hymenaea courbaril to gather information on how they respond in the four seasons of the year. Analyzing the collected data to evaluate the correlation between CO 2 assimilation and environmental variables.
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5 EXPERIMENTAL PART The plants were placed on a stand covered with dark mesh. Instituto de Botânica – São Paulo Measurement were made in eight young plants of jatobá.
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6 EXPERIMENTAL PART Portable photosynthesis system LI-6400 Variables measured: Net photosynthesis Carbon dioxide concentrations Relative humidity Photosynthetically Active Radiation (PAR) Air temperature
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7 Level I Level II Level III Ápice Eófilo Leaf Folíolo knot EXPERIMENTAL PART Measurements: April 2001 to March 2002. Twice a week, four plants a day. From 6:20 a.m. to 6:00 p.m. At three levels of the plants. Data were collected every hour.
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8 RESULTS Carbon dioxide assimilation in jatobá corresponding to the four seasons
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9 RESULTS Characteristics of the CO 2 assimilation in jatobá in the four seasons. CharacteristicAutumnWinterSpringSummer The largest photosynthesis values at about 7 a.m. (µmol CO 2.m -2.s -1 ) 0.81.2 2.51.7 Time period in which the largest photosynthesis values were reached, for each season 11 a.m. – 12 a.m. 11 a.m. – 1 p.m. 8 a.m. – 10 a.m. 9 a.m. – 1 p.m. The largest photosynthesis values for each season (µmol CO 2.m -2.s -1 ) ~ 5.5~ 5.0~ 6.0~ 4.5 Time in which photosynthesis values are smaller than 0.5 µmol CO 2.m -2.s -1 ~ 4 p.m.~ 5 p.m. ~ 6 p.m.
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10 RESULTS Results of the correlation analysis between photosynthesis and the environmental variables. VariablesCorrelation Air temperature (Tair)0.195996 Reference CO 2 concentration (CO 2 _R)-0.003160 Sample CO 2 concentration (CO 2 _S)-0.076570 Reference Relative Humidity (RH_R)-0.274220 Sample Relative Humidity (RH_S)-0.205780 In-chamber PAR (PARi)0.613364 External PAR (PARo)0.624344
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11 CONCLUSION Results show that the largest photosynthesis rates occur during spring, but the largest photosynthesis period happens in summer. A correlation of 0.6 was found between photosynthesis and PAR, and correlations smaller than 0.3 with the other environmental variables. The great amount of data collected showed relevant characteristics of the seasonal behavior of photosynthesis in jatobá and can be further explored.
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