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Relationship between photosynthesis and leaf nitrogen concentration in ambient and elevated [CO2] in white birch seedlings.
- Source :
- Tree Physiology; Jun2007, Vol. 27 Issue 6, p891-899, 9p, 1 Chart, 6 Graphs
- Publication Year :
- 2007
-
Abstract
- To study the effects of elevated CO<subscript>2</subscript> concentration ([CO<subscript>2</subscript>]) on relationships between nitrogen (N) nutrition and foliar gas exchange parameters, white birch (Betula papyrifera Marsh.) seedlings were exposed to one of five N-supply regimes (10, 80, 150, 220, 290 mg Nl<superscript>-1</superscript>) in either ambient [CO<subscript>2</subscript>] (360 µmol mol<superscript>-1</superscript>) or elevated [CO<subscript>2</subscript>] (720 µmol mol<superscript>-1</superscript>) in environment-controlled greenhouses. Foliar gas exchange and chlorophyll fluorescence were measured after 60 and 80 days of treatment. Photosynthesis showed a substantial down-regulation (up to 57%) in response to elevated [CO<subscript>2</subscript>] and the magnitude of the down-regulation generally decreased exponentially with increasing leaf N concentration. When measured at the growth [CO<subscript>2</subscript>], elevated [CO<subscript>2</subscript>] increased the overall rate of photosynthesis (P<subscript>n</subscript>) and instantaneous water-use efficiency (IWUE) by up to 69 and 236%, respectively, but decreased transpiration (E) and stomatal conductance (g<subscript>s</subscript>) in all N treatments. However, the degree of stimulation of photosynthesis by elevated [CO<subscript>2</subscript>] decreased as photosynthetic down-regulation increased from 60 days to 80 days of treatment. Elevated [CO<subscript>2</subscript>] significantly increased total photosynthetic electron transport in all N treatments at 60 days of treatment, but the effect was insignificant after 80 days of treatment. Both P<subscript>n</subscript> and IWUE generally increased with increasing leaf N concentration except at very high leaf N concentrations, where both P<subscript>n</subscript> and IWUE declined. The relationships of P<subscript>n</subscript> and IWUE with leaf N concentration were modeled with both a linear regression and a second-order polynomial function. Elevated [CO<subscript>2</subscript>] significantly and substantially increased the slope of the linear regression for IWUE, but had no significant effect on the slope for P<subscript>n</subscript>. The optimal leaf N concentration for P<subscript>n</subscript> and IWUE derived from the polynomial function did not differ between the CO<subscript>2</subscript> treatments when leaf N was expressed on a leaf area basis. However, the mass-based optimal leaf N concentration for P<subscript>n</subscript> was much lower in seedlings in elevated [CO<subscript>2</subscript>] than in ambient [CO<subscript>2</subscript>] (31.88 versus 37.00 mg g<superscript>-1</superscript>). Elevated [CO<subscript>2</subscript>] generally decreased mass-based leaf N concentration but had no significant effect on area-based leaf N concentration; however, maximum N concentration per unit leaf area was greater in elevated [CO<subscript>2</subscript>] than in ambient [CO<subscript>2</subscript>] (1.913 versus 1.547 g N m<superscript>-2</superscript>). [ABSTRACT FROM AUTHOR]
- Subjects :
- PHOTOSYNTHESIS
PAPER birch
TAIGAS
CLIMATE change
CARBON dioxide
Subjects
Details
- Language :
- English
- ISSN :
- 0829318X
- Volume :
- 27
- Issue :
- 6
- Database :
- Complementary Index
- Journal :
- Tree Physiology
- Publication Type :
- Academic Journal
- Accession number :
- 53298242
- Full Text :
- https://doi.org/10.1093/treephys/27.6.891