Abstract
1. It was observed that on the germination of higher plants, ω-methyl pantethine and bis (N-methyl pantoyl β-aminoethyl) disulfide, the compounds supposed to be the analogues of pantethine level, act similarly to ω-methyl pantothenic acid as a pantothenic acid antimetabolite. Inhibition by ω-methyl pantethine may be almost perfectly prevented by addition of pantothenic acid, but that by bis (N-methyl pantoyl β-aminoethyl) disulfide can be only partially prevented.
2. An experiment was conducted to quantitatively evaluate this inhibition on germination with the following results: In barley, 10 mM ω-methyl pantothenic acid was effective in fully inhibiting the germination and this inhibition was perfectly eliminated by addition of 0.1 mM pantothenic acid, the inhibition index being 100:1. Moreover, this inhibition could only partially be eliminated even by addition of pantoyl lactone in large quantities. However, the inhibition by ω-methyl pantoyl lactone was eliminated by 1/20 of pantoyl lactone. From this it was surmised that even in the process of germination pantothenic acid synthesis takes place with pantoic acid which acts as a precursor to this synthesis.
3. It was revealed that the inhibitory action of pantothenic acid analogues depend on the species of the plants on which they act.
Dicotyledoneous plants were all markedly inhibited by the analogues in general, and monocotyledoneous plants were classified into two groups according to the actions; one was affected and the other resistant to the action of the analogues. For instance, barley (belong to Festucoideae-subfamily) was markedly inhibited by ω-methyl pantothenic acid, whereas rice-plant (Panicoideae-subfamily) was resistant to the action. Thus, it was proved that the difference between two types of Gramineae plants in sensitivity to the effects of antimetabolites depends upon the difference in subfamily.
4. Difference in the effects cf pantothen is acid analogues depending on the species of plants was discussed in comparison with other physiological characteristics on germination. It ws suggested that the difference between species of plants in sensitivity may be concerned with its pattern of respiratory function.
