Effects of low and elevated CO2 on C3 and C4 annuals. I. Growth and biomass allocation

• Published in: Oecologia 1995, Vol.101 (1), p.13-20
• Main Authors: Dippery, J.K, Tissue, D.T, Thomas, R.B, Strain, B.R
• Format: Article
• Language: English
• Subjects: Abutilon theophrasti; Amaranthus retroflexus; Animal and plant ecology; Animal, plant and microbial ecology; Annuals; atmosphere; Autoecology; Biological and medical sciences; Biomass; Biomass production; C3 photosynthesis; C3 plants; C4 photosynthesis; carbon dioxide; carbon dioxide enrichment; dry matter accumulation; dry matter partitioning; Fundamental and applied biological sciences. Psychology; growth rate; Leaf area; leaves; low carbonw dioxide levels; photosynthesis; Plant age; Plant growth; Plants; Plants and fungi; Root biomass; root shoot ratio; roots; Stems
• ISSN: 0029-8549; 1432-1939
• DOI: 10.1007/BF00328894

In order to study C₃ and C₄ plant growth in atmospheric CO₂ levels ranging from past through predicted future levels, Abutilon theophrasti (C₃) and Amaranthus retroflexus (C₄) were grown from seed in growth chambers controlled at CO₂ partial pressures of 15 Pa (below Pleistocene minimum), 27 Pa (pre-industrial), 35 Pa (current) and 70 Pa (predicted future). After 35 days of growth, CO₂ had no effect on the relative growth rate, total biomass or partitioning of biomass in the C₄ species. However, the C₃ species had greater biomass accumulation with increasing CO₂ partial pressure. C₃ plants grown in 15 Pa CO₂ for 35 days had only 8% of the total biomass of plants grown in 35 Pa CO₂. In 15 Pa CO₂, C₃ plants had lower relative growth rates and lower specific leaf mass than plants grown in higher CO₂ partial pressures, and aborted reproduction. C₃ plants grown in 70 Pa CO₂ had greater root mass and root-to-shoot ratios than plants grown in lower CO₂ partial pressures. These findings support other studies that show C₃ plant growth is more responsive to CO₂ partial pressure than C₄ plant growth. Differences in growth responses to CO₂ levels of the Pleistocene through the future suggest that competitive interactions of C₃ and C₄ annuals have changed through geologic time. This study also provided evidence that C₃ annuals may be operating near a minimum CO₂ partial pressure for growth and reproduction at 15 Pa CO₂.