Responses to Root-Zone CO2 Enrichment and Hypoxia of Wheat Genotypes Differing in Waterlogging Tolerance
1997
Huang, Bingru | Johnson, Jerry W. | NeSmith, D Scott
Knowledge of wheat (Triticum aestivum L.) responses to CO₂ and O₂ in the root environment could improve understanding of the mechanisms of waterlogging tolerance and thus help develop waterlogging tolerance wheat plants. This experiment was designed to investigate the responses to elevated CO₂ and hypoxia of two wheat genotypes, Bayles and Savannah, which differ in waterlogging tolerance. Plants were grown in a growth chamber in nutrient solutions. Nutrient solutions were bubbled with ambient air (control), N₂ containing 5 kPa O₂ and ambient CO₂ (hypoxia), N₂ containing 10 kPa CO₂ and ambient O₂ (high CO₂, ambient O₂), and N₂ containing 10 kPa CO₂ and 5 kPa O₂ (high CO₂, low O₂). Hypoxia alone had adverse effects on net photosynthesis (Pₙ), stomatal conductance (gₛ), water relations, chlorophyll (chl) content, and shoot and root growth. The effects were greater for waterlogging-sensitive Bayles. When compared with the aerated control, the combination of elevated CO₂ and hypoxia caused significant reductions in Pₙ, gₛ, leaf water potential, and leaf chl content for Bayles, and in shoot and root growth for both Bayles and Savannah. Photosynthetic rate and leaf chi content of Savannah were increased when roots of hypoxic plants were exposed to elevated CO₂, but this was not true for Bayles. Root-zone CO₂ enrichment at ambient O₂ had no significant effects on shoot growth, but reduced root growth in both genotypes. The results showed that CO₂ enrichment under root hypoxia can alleviate some negative effects of hypoxia on Pₙ, leaf chi content, and shoot growth, the effect being larger for waterlogging tolerance Savannah.
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