This paper describes the properties germination inhibitor in onion juice and its inhibiting mechanism.
1. Germination inhibitor was found in ether extracts obtained from onion juice. This was soluble in organic solvents, insoluble in water. This substance had Rf value of 0.81.0 with isopropanol-ammonia-water (1.0: 1: 1v/v) using strips of Toyo Roshi No. 51.
A large amount of inhibitor was found in rest bulbs as compared with sprouted one. Ohshu variety having a deep and long rest had less amount of inhibitor than Senshu-ki variety having a moderate rest.
These results suggested that the germination inhibitor in onion juice was not considered to be a main factor in connection with rest phenomenon of bulbs.
2. This substance was identified as allylsulfide group by ultra-violet spectrum, Rf value and special odor. Microchemical observation showed that the inhibitor was accumulated with bulb thickening, reached a maximum peak at harvest time and then decreased with sprouting, and that at harvest time higher concentrations of the inhibitor were found in neck and outer part of bulb.
3. The inhibition of germination with ether extracts was recovered to some extent by addition of 10-1 and 10-3 mole cysteine solution. These facts suggest that allylsulfide may inhibit the activity of the sulfhydryl enzymes. Consequently germination inhibitor could be a inbibitor of sulphydryl enzyme.
