Growth and Photosynthetic Responses of One C₃ and Two C₄ Chenopodiaceae Plants to Three CO₂ Concentration Conditions
2008
Ishikawa, Shin-Ichi (Gunma University, Maebashi, Gunma, Japan), E-mail: [email protected]
Growth and photosynthetic responses of one C₃ and two C₄ plants in the family Chenopodiaceae in three CO₂ concentration ([CO₂]) conditions-low (about 243 μmol mol-¹, LC), present (about 378, PC), and high (about 465, HC)-were investigated in open top chambers. The relative growth rate (RGR) and net assimilation rate in the C₃ plant, Chenopodium album, increased with increasing [CO₂], though the RGR was not enhanced significantly in the HC condition. The leaf area ratio and leaf weight ratio of the C₃ plant drastically decreased with increasing [CO₂], suggesting that the C₃ plant invests more biomass to leaves in lower [CO₂] conditions. The two C₄ plants, Atriplex glauca and A. lentiformis, showed relatively small changes in those growth parameters. These photosynthetic-pathway-dependent responses suggest that growth patterns of C₃ and C₄ plants have been altered by past increases in atmospheric [CO₂] but that there will be relatively little further alteration in the future high-CO₂ world.
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