1972 Volume 41 Issue 4 Pages 488-495
This paper forms the third part of a series of investigations on the control of the breaking of dormancy in barnyardgrass (Echinochloa Crusgalli var. oryzicola Ohwi) seed. This investigation evaluated the dormancy-breaking effect of various compounds concerning with endogenous oxidation-reduction system and the change of its effect through the dormancy-breaking process. 1) In deep dormancy stage, hydroquinone and benzoquinone showed a stimulative effect on the breaking of dormancy in considerable degree. Moreover, as the dormancy became shallow, the effect of these compounds was higher than in deep stage. 2) In shallower dormancy stage, guaiacol, resorcinol and L-ascorbic acid had effect as remarkable as hydroquinone. However, no effect was shown by pyrogallol and catechol in any dormancy stage. 3) In shallow stage, o-cresol showed a marked effect on the breaking of dormancy, but m- and p-cresol had no effect. 4) There is no relationship between the dormancy-breaking effect and the inhibition of oxygen up-take, comparing with guaiacol, resorcinol, catechol and pyrogallol treatments. The results obtained suggest that the inhibition of tyrosinase (polyphenol oxidase) is the critical factor in the dormancy-breaking action of hydroquinone, resorcinol, quaiacol and L-ascorbic acid, which are known not to be substrates of tyrosinase and to be inhibitors of the enzyme.
