Relationships between needle nitrogen concentration and photosynthetic responses of Douglas-fir seedlings to elevated CO sub(2) and temperature

• Published in: The New phytologist Vol. 162; no. 2; pp. 355 - 364
• Main Authors: Lewis, J D, Lucash, M, Olszyk, D M, Tingey, D T
• Format: Journal Article
• Language: English
• Published: 01.05.2004
• Subjects: Pseudotsuga menziesii
• ISSN: 0028-646X; 1469-8137
• DOI: 10.1111/j.1469-8137.2004.01036.x

Here we examined correlations between needle nitrogen concentration ([N]) and photosynthetic responses of Douglas-fir (Pseudotsuga menziesii) seedlings to growth in elevated temperatures and atmospheric carbon dioxide concentrations ([CO sub(2)]). Seedlings were grown in sunlit, climate-controlled chambers at ambient or ambient +3.5 degree C and ambient or ambient +180 mu mol mol super(-1) CO sub(2) in a full factorial design. Photosynthetic parameters and needle [N] were measured six times over a 21-month period. Needle [N] varied seasonally, and accounted for 30-50% of the variation in photosynthetic parameters. Across measurement periods, elevated temperature increased needle [N] by 26% and light-saturated net photosynthetic rates by 17%. Elevated [CO sub(2)] decreased needle [N] by 12%, and reduced net photosynthetic rates measured at a common [CO sub(2)], maximum carboxylation activity (V sub(c,max)) and electron transport capacity (J sub(max)), indicating photosynthetic acclimatization. Even so, elevated [CO sub(2)] enhanced net photosynthesis, and this effect increased with needle [N]. These results suggest that needle [N] may regulate photosynthetic responses of Douglas-fir to climate change. Further, needle [N] may be altered by climate change. However, effects of elevated [CO sub(2)] on photosynthesis may be similar across growth temperatures.