Abstract
This paper reports the physical factor in onion juice.
1. It was clearly shown that ether-insoluble fraction in onion juice remarkably depressed the seed germination.
2. It was also shown that the same concentration of NaCl or KNO3 solutions as that of onion juice inhibited both germination of seeds and growth of onion seedlings, and that the addition of ether extracts obtained from onion juice to Nacl solution enhanced the inhibition of seed germination more than NaCl solution only.
3. Refractometer index of onion juice increased with bulb thickening and reached a maximum value a month later followed by a gradual decline.
The inhibition of seed germination by onion juice was significantly correlated with the refractometer index of it.
4. Ohshu, a late variety, showed higher value in refractometer index of juice and more strong inhibition of seed germination than Senshu-Ki, a middle one.
5. The effect of concentration of reducing sugar and sucrose as substrate on the respiration metabolism of terminal part of stem disk or crude enzyme with Warburg manometer suggested that the same concentration of substrate as that of onion juice depressed considerably the respiration.
6. On the basis of foregoing results it was concluded that sugar accumulation accompanied with bulbing induces the depression of respiration metabolism, resulted in rest in bulb, and that the gradual decline in sugar concentration by respiration in bulb during storage allows the terminal bud to renew the growth.
