Response of Two Wheat Cultivars to CO(2) Enrichment under Subambient Oxygen Conditions.

Two cultivars of wheat (Triticum aestivum L. cvs Sonoita and Yecora Rojo) were grown to maturity in a growth chamber within four sub-chambers under two CO(2) levels (350 or 1000 microliters per liter) at either ambient (21%) or low O(2) (5%). Growth analysis was used to characterize changes in plant carbon budgets imposed by the gas regimes. Large increases in leaf areas were seen in the low O(2) treatments, due primarily to a stimulation of tillering. Roots developed normally at 5% O(2). Seed development was inhibited by the subambient O(2) treatment, but this effect was overcome by CO(2) enrichment at 1000 microliters per liter. Dry matter accumulation and seed number responded differently to the gas treatments. The greatest dry matter production occurred in the low O(2), high CO(2) treatment, while the greatest seed production occurred in the ambient O(2), high CO(2) treatment. Growth and assimilation were stimulated more by either CO(2) enrichment or low O(2) in cv Yecora Rojo than in Sonoita. These experiments are the first to explore the effect of whole plant low O(2) treatments on growth and reproduction. The finding that CO(2) enrichment overcomes low O(2)-induced sterility may help elucidate the nature of this effect.