© 2007 Heron Publishing—Victoria, Canada
Interaction of drought and elevated CO2 concentration on photosynthetic down-regulation and susceptibility to photoinhibition in Japanese white birch seedlings grown
with limited N availability
Mitsutoshi Kitao (1,2), Thomas T. Lei (1,3), Takayoshi Koike (1,4), Masazumi Kayama (1), Hiroyuki Tobita (1) and Yutaka Maruyama (1)
1. Hokkaido Research Center, Forestry and Forest Products Research Institute, Sapporo 062-8516, Japan / 2. Corresponding author (kitao@ffpri.affrc.go.jp) / 3. Department of Environmental Solution Technology, Ryukoku University, Shiga 520-2194, Japan / 4. Hokkaido University Forests, FSC, Sapporo 060-0809, Japan / Received December 16, 2005; accepted June 5, 2006; published online February 1, 2007
Summary
The interaction of drought and elevated carbon dioxide concentration ([CO2]) on carboxylation capacity of Rubisco (Vcmax) and susceptibility to photoinhibition may be an important determinant of plant responses to seasonal fluctuations in precipitation
in an anticipated elevated [CO2] environment. Japanese white birch (Betula platyphylla var. japonica) leaves that developed wholly during a period of drought showed an increase in leaf nitrogen and a decrease in leaf carbohydrates
that could ameliorate photosynthetic down-regulation, defined as a decrease in Vcmax in response to elevated [CO2]. Photochemical quenching (qP) was decreased by elevated [CO2] but increased by drought when compared at a given intercellular [CO2] (Ci), indicating that elevated [CO2] could increase the risk of photoinhibition, whereas long-term drought could alleviate the risk of photoinhibition. However,
only a small variation in qP was measured among seedlings in the various water availability × [CO2] treatment combinations, consistent with the small treatment differences in chronic photoinhibition among the seedlings,
as indicated by the ratio of variable to maximum chlorophyll fluorescence after overnight dark-adaptation. Our results suggest
that the offsetting responses—reduced Vcmax plus increased Ci at elevated [CO2] and increased Vcmax plus reduced Ci under drought conditions—resulted in a narrow range of susceptibility to photoinhibition at the growth [CO2] in Japanese white birch seedlings grown in various water availability × [CO2] treatment combinations.
Keywords:
Betula platyphylla, electron transport rate, leaf N concentration, leaf sugar and starch concentration, photochemical quenching, shoot/root
ratio.
