Journal Article

Low moisture availability inhibits the enhancing effect of increased soil temperature on net photosynthesis of white birch (<i>Betula papyrifera</i>) seedlings grown under ambient and elevated carbon dioxide concentrations

Titus F. Ambebe and Qing-Lai Dang

in Tree Physiology

Volume 29, issue 11, pages 1341-1348
Published in print November 2009 | ISSN: 0829-318X
Published online November 2009 | e-ISSN: 1758-4469 | DOI: http://dx.doi.org/10.1093/treephys/tpp079
Low moisture availability inhibits the enhancing effect of increased soil temperature on net photosynthesis of white birch (Betula papyrifera) seedlings grown under ambient and elevated carbon dioxide concentrations

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White birch (Betula papyrifera Marsh.) seedlings were grown under two carbon dioxide concentrations (ambient: 360 μmol mol−1 and elevated: 720 μmol mol−1), three soil temperatures (5, 15 and 25 °C initially, increased to 7, 17 and 27 °C, respectively, 1 month later) and three moisture regimes (low: 30–40%; intermediate: 45–55% and high: 60–70% field water capacity) in greenhouses. In situ gas exchange and chlorophyll fluorescence were measured after 2 months of treatments. Net photosynthetic rate (A n) of seedlings grown under the intermediate and high moisture regimes increased from low to intermediate T soil and then decreased to high T soil. There were no significant differences between the low and high T soil, with the exception that A n was significantly higher under high than low T soil at the high moisture regime. No significant T soil effect on A n was observed at the low moisture regime. The intermediate T soil increased stomatal conductance (g s) only at intermediate and high but not at low moisture regime, whereas there were no significant differences between the low and high T soil treatments. Furthermore, the difference in g s between the intermediate and high T soil at high moisture regime was not statistically significant. The low moisture regime significantly reduced the internal to ambient CO2 concentration ratio at all T soil. There were no significant individual or interactive effects of treatment on maximum carboxylation rate of Rubisco, light-saturated electron transport rate, triose phosphate utilization or potential photochemical efficiency of photosystem II. The results of this study suggest that soil moisture condition should be taken into account when predicting the responses of white birch to soil warming.

Keywords: boreal trees; chlorophyll fluorescence; CO2 enrichment; global change; stomatal and non-stomatal limitations

Journal Article.  6017 words.  Illustrated.

Subjects: Plant Sciences and Forestry

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