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A Colorimetric Method for Assaying Dissolved Oxygen Loss from Container-Grown Rice Roots

Wetland Biogeochemistry Institute, Louisiana State Univ., Baton Rouge, LA 70803-7511

^* Corresponding author

ABSTRACTAlthough not easily measured, oxygen release from rice (Oryza sativa L.) roots determines the plant's ability to survive reducing conditions. Our main objective was to test titanium-citrate complex for its potential to quantify dissolved 02 concentrations in solutions bathing the whole root system of container-grown rice cuitivars. Influences of aeration status on root aerenchyma formation and radial oxygen loss from roots were also evaluated. Seven rice cultivars were grown in sand culture fertilized with nutrient solution under well drained and hypoxic conditions. Oxygen concentration was measured colorimetrically 6 h after placing plant roots in the Ti³⁺-citrate solution. Plants were harvested for root porosity and radial oxygen loss estimates at 14 and 35 d after transplanting. Estimates of radial oxygen loss with the Ti³⁺-citrate technique were comparable to those obtained with a polarographic oxygen electrode. Both radial oxygen loss and root porosity were enhanced by hypoxia. Rapid formation of aerenchyma at early growth stages coupled with correspondingly high 02 leakage from roots may explain why some rice cultivars cope with the adverse effects of anaerobiosis better than other cultivars.

Received for publication October 14, 1992.