With the purpose of finding some clue as to the physiological mechanism of tuberous roots formation, the studies were set about roots respiration by the use of Warburg's manometer. Following results were obtained. 1. Oxygen uptake of roots at varying pH of buffer solution from 4.2 to 7.6 showed a little change, but optimal region was found at pH 6-7. 2. It was found that the temperature coefficient (Q10) of oxygen uptake by tuber disks in air was 3-4 at temperature from 21 to 32°C. This was larger than the Q10 of fiberous roots or intact tuber. Both the Q10 of tuber disks and fiberous roots decreased in water compared with the Q10 in air. 3. Oxygen uptake of the roots in water markedly decreased, though CO2 output was less changeable compared with the respiration in air. Rate of decreasing of O2 uptake in water was different among kinds of roots, small diameter, large diameter and tuberous. The O2 uptake of roots in water decreased considerably by removing of lateral roots. 4. Oxygen uptake of roots in gas phase increased with O2 concentration up to 20 per cent. O2 uptake of roots in water increased in proportion to O2 concentration of gas phase in Warburgvessel over 20 per cent., however, there was difference of increased rate between the large diameter roots and small diameter roots. 5. Oxyge uptake of tuber disks increased in inverse proportion to the thickness of disk from 500 μ to 3000 μ. Respiratory rate of disks with the thickness of 500 μ was more than three times compared with that of an equivalent masks of intact tuber. 6. Respiratory rate of roots decreased rapidly until about 30 days from planting and decreased gradually thereafter. Respiratory rate of fiberous roots increased from the base toward the tip of roots both in water and in air. But, there was difference of respiration rate in water among parts of tuberous root, joint, flesh and tail. 7. Respiratory rate of tuber disks was promoted by 2, 4-dinitrophenol (2.5 × 10-5 Mol) and inhibited by potassium cyanide (10-4 Mol) and monoiodoacetic acid (10-3 Mol) though the effects of these on fiberous roots were little. It was supposed that such difference in respiration may be due to the qualitative difference between tuber disks and fiberous roots.
