Effects of Elevated CO2 on Photosynthetic Induction in two Populus Species
Tomimatsu, H. and Tang, Y. 2012. Elevated CO2 differentially affects photosynthetic induction response in two Populus species with different stomatal behavior. Oecologia 169: 869-878.
Working with two Populus genotypes with different stomatal responses to changes in light intensity - Populus koreana x trichocarpa cv. Peace (which shows a minimal stomatal response to PFD change) and P. euramericana cv. I-55 (which has a normal stomatal response to PFD change) - Tomimatsu and Tang grew the two genotypes under three CO2 regimes (380, 700 and 1020 ppm) for a period of two months, whereupon they measured leaf photosynthetic rates during a sudden PFD increase from 20 to 800 µmol/m2/sec, in order to assess the photosynthetic induction time (IT) required for the CO2 uptake rate to reach 50% (IT50) and 90% (IT90) of the steady-state photosynthetic rate following the increase in PFD.
Results of the analysis revealed, in the words of the two researchers, that "photosynthetic induction times, both IT50 and IT90, were significantly shorter in plants grown in high CO2 regimes in the two poplar genotypes, which is consistent with an increase in the induction state under high CO2 regimes," as suggested by the work of Tinoco-Ojanguren and Pearcy (1993), Pearcy et al. (1994) and Valladares et al. (1997).
In describing the significance of their results, Tomimatsu and Tang write that their study suggests that "leaf carbon gain would increase under high CO2 environments in response to light fluctuations based on the reduction in photosynthetic induction observed" in their experiment. And they say that Leakey et al. (2005) and Niinemets (2007) suggest that "the stimulation of photosynthesis under high CO2 and fluctuating light conditions may lead to increases in seedling growth and future survival in the understory." In addition, Tomimatsu and Tang write that "climate change may particularly increase CO2 levels in the understory in closed canopies, and thus the increase in leaf carbon gain of photosynthetic induction under high CO2 regimes may further add to whole canopy photosynthesis," in support of which conclusion they cite the studies of Buchmann et al. (1997), Holtum and Winter (2001), Leakey et al. (2005) and Niinemets (2007).
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