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Physiology and Growth of Wheat Across a Subambient Carbon Dioxide Gradient

H. WAYNE POLLEY, HYRUM B. JOHNSON, HERMAN S. MAYEUX and STEPHEN R. MALONE
Annals of Botany
Vol. 71, No. 4 (April 1993), pp. 347-356
Published by: Oxford University Press
Stable URL: http://www.jstor.org/stable/42758835
Page Count: 10
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Physiology and Growth of Wheat Across a Subambient Carbon Dioxide Gradient
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Abstract

Two cultivars of wheat (Triticum aestivum L.), 'Yaqui 54' and 'Seri M82', were grown along a gradient of daytime carbon dioxide concentrations ([CO₂]) from near 350-200 µmol CO₂ mol⁻¹ air in a 38 m long controlled environment chamber. Carbon dioxide fluxes and evapotranspiration were measured for stands (plants and soil) in five consecutive 7·6-m lengths of the chamber to determine potential effects of the glacial/interglacial increase in atmospheric [CO₂] on C₃ plants. Growth rates and leaf areas of individual plants and net assimilation per unit leaf area and daily (24-h) net CO₂ accumulation of wheat stands rose with increasing [CO₂]. Daytime net assimilation (PD, mmol CO₂ m⁻² soil surface area) and water use efficiency of wheat stands increased and the daily total of photosynthetic photon flux density required by stands for positive CO₂ accumulation (light compensation point) declined at higher [CO₂]. Nighttime respiration (RN, mmol CO₂ m⁻² soil surface) of wheat, measured at 369-397 µmol mol⁻¹ CO₂, apparently was not altered by growth at different daytime [CO₂], but RN/PD of stands declined linearly as daytime [CO₂] and PD increased. The responses of wheat to [CO₂], if representative of other C₃ species, suggest that the 75-100% increase in [CO₂] since glaciation and the 30 % increase since 1800 reduced the minimum light and water requirements for growth and increased the productivity of C₃ plants.

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