Effects of air temperature and transitory CO2 availability on carbon assimilation in tropical woody species Swietenia macrophylla King, and Copaifera langsdorffi Desf.
Carlos
Henrique
Prado, Laboratory of Plant Physiology, Department of Botany, Federal University of Sao Carlos, SP, 13565-905, Brazil, caique@power.ufscar.br
(Presenting)
Zhang
Chengjun, Key Laboratory of Forest Plant Ecology, Northeast Forestry University, Harbin 150040, P. R. China, zhangcj211@hotmail.com
Leonnardo
Lopes
Ferreira, Laboratory of Plant Physiology, Department of Botany, Federal University of Sao Carlos, SP, 13565-905, Brazil, leonnardo@lycos.co.uk
After to display aerial plant part of seedlings of Swietenia macrophylla (mahogany) and Copaifera lagsdorffi (copaiba) to different overnight temperatures (13–35 ºC), the leaf net photosynthetic rate (A) was investigated by measuring photosynthetic light-response curves at 360 mmol mol-1 CO2, and photosynthetic CO2-response curves at light-saturated intensity (1500 mmol m-2 s-1). The optimal temperature for photosynthesis (OTP) measured at regular CO2 concentration (360 mmol mol-1) was 28,0ºC in S. macrophylla and 23,0ºC in C. langsdorffii. These OTP values shifted upward 5ºC under CO2 saturation. At temperature below 25 ºC, the decline in A was mainly due to the drop in carboxylation efficiency (Ce), while temperature was over 31 ºC, the reduction in A resulted from decrease in Ce, increase in both leaf respiration and photorespiration. The CO2-induced stimulation of photosynthesis was strongly inhibited at temperatures below 16 ºC. The results showed that, the leaf photosynthetic process of tropical evergreen plants should not be accelerated at low temperature in winter season under elevated CO2 concentration in the future if diurnal local mean temperature decreases beyond 16ºC. On the other hand, the OTP values could change significantly upward (5ºC) under atmospheric CO2 concentration able to saturate photosynthetic process. These results pointed out that both ambient factors changed by the greenhouse effect (air temperature and atmospheric CO2 availability) could act simultaneously on photosynthesis in a complex approach. Under elevated CO2 concentration low temperatures remove photosynthesis stimulation; and high temperatures increase negative components of carbon balance (respiration/photorespiration) and change photosynthetic biochemical machinery shifting upward OTP values.
Submetido por Carlos Prado em 23-MAR-2004
Tema Científico do LBA: CD (Armazenamento e Trocas de Carbono)