Studies on the Germination of Seeds of Bupleurum falcatum L. : IV. The germination inhibitors of Bupleurum falcatum seeds

Abstract

In the previous article, it was suggested that oxygen consumption by seed coats was associated with a mechanism of dormancy in Bupleurum falcatum seeds, and that the seed coats contained germination inhibitors. In these experiments, the germination inhibitors which were related to the oxygen absorption, were isolated from the seed coats of Bupleurum falcatum seeds, and then, the physiological properties of germination inhibitors had been investigated. The results obtained are as follows: 1. The germination inhibitors were extracted with methyl alcohol from such experimental materials as intact seeds, stripped seeds and seed coats. The inhibition by the extract of the seed coats showed higher activity than other two materials. 2. The ethyl ether fraction obtained from seed coats clearly inhibited the germination in lettuce seeds, and the rate of oxygen absorption in water by the ethyl ether fraction was also higher than the other two fractions. 3. Ethyl ether fraction was divided into three parts: precipitate, sodium hydro-gencarbonate fraction, and sodium carbonate fraction. Significant inhibition of germination in lettuce seeds was recognized in the two fractions of precipitate and sodium hydro-gencarbonate. These substances were denoted as inhibitors A and B, respectively. 4. Inhibitors A and B showed the inhibition of germination in lettuce seeds and increased oxygen absorption in dormant Bupleurum falcatum seeds. The physiological activities of inhibitor B were higher than those of inhibitor A, even though the growth inhibition in lettuce seeds were only observed by inhibitor A. 5. On the paper chromatograms using the solvent of ammonia saturated n-butyl alcohol, five spots were found from inhibitor A, while six spots were from inhibitor B. But the inhibition of germination in lettuce seeds was observed only in one spot of inhibitor B which showed the typical color reaction with the phenol reagents.