Further Evidence of Oxygen Diffusion as the Determining Factor in the Relation Between Disk Thickness and Respiration of Potato Tissue

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Abstract
The effect of SjjiTension above atmospheric pO2 on the development of respiratory capacity in potato disks has been examined. Raising the O2 tension of the aqueous environment to 40% during the aging of 2.0 mm or 3.0 mm thick disks at 25 [degree] progressively increased the respiration rate of the tissue as shown by subsequent assay in 100% O2. Disks 3.0 mm thick showed a greater response to increase pO2 than did 2.0 mm disks. A comparison of center 1.0 mm sections excised from 3.0 mm disks after aging, showed that the respiration rate of internal tissue from disks aged in high pO2 was approximately 40% greater than such tissue aged with atmospheric pO2. The characteristic inverse relationship between respiration rate and thickness in aged disks can be modified from a concave-downwards curve to a convex-downwards curve by pretreating the tissue with increased pO2, thus indicating that raising the pO2 during aging can increase the thickness threshold at which the transition from tissue manifesting the respiratory characteristics of thin disks to that manifesting the characteristics of thick disks, occurs. Similarly increased pO2 during aging can modify the hyperbolic relationship obtaining between pretreatment temperature in the range 10[degree] to 25[degree] and respiratory capacity of aged 3.0 mm disks, to approximately to the linear relationship observed with 0.75 mm disks. It is concluded that the development of respiratory capacity in disks between 0.75 mm and 3.0 mm thick is restricted by O2 deficiency and that the characteristic inverse relationship between respiration rate and thickness in aged disks is largely attributable to this factor, the influence of which is discernible both on the development of respiratory capacity and on its subsequent assay.

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