EFFECT OF VARIOUS OXYGEN AND CARBON DIOXIDE CONCENTRATIONS ON COTTON ROOT DEVELOPMENT

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Abstract
Cotton seedlings of the Stoneville 2B var. were grown in nutrient solns., with the roots subjected to different concs. of O2 and CO2. Cotton root growth did not occur at concs. of 0.5% O2 or less. Opt. root growth occurred at concs. of 7.5-21% 62, while root growth was considerably depressed at 90 or 100% O2. In these tests, CO2 was held constant at 10%, except when pure gases were used. The influence of CO2 on cotton root growth was studied with O2 held constant at 21%. Cotton root growth was unaffected by concs. of CO2 up to 15%, was reduced about 1/2 at 30%, greatly reduced at 45% and was inhibited at 60% CO2. Tests were made to determine whether the tolerance of cotton roots to poor aeration could be affected by the form in which N was supplied to the nutrient solns. Tap root growth at each conc. of O2 was similar with both nitrate and ammonium N.