Abstract
The results in the previous paper in this series have shown that dormancy in rice seed is caused by the inhibitors contained in the hulled seed as well as those in the hull, and it is broken by the decrease of their quantities. In this study, the inhibitors contained in each of three organs ; embryo, endosperm, and hull, were examined by means of the biological and chemical determintions. And auxin was also determined with the same methods. The results obtained are summarized as follows:
1. Two inhibitors in the dormant rice seed existed in all organs, i. e. embryo, endosperm, and hull, with nearly equal biological activities. Consequently, if the activities of the inhibitors of each organ are calculated in term of one-seed, the almost equal quantities of the inhibitors are distributed in each organ, and it is noticeable that embryo contains, in spite of its relatively very small body, as much the inhibi tors as other organs.
On the basis of previous and this results, the breaking of dormancy by husking treatment seems to be brought about by not only the removal of the inhibitors in hull but also the inactivation of inhibitors in embryo and endosperm, which may be caused by the increasing of oxygen entrance into their their tissue. It further may be satisfactorily considered that the respective biological determination of the inhibitors contained in three organs which differ muturally in genetical constitution may become a effective means to clarify more the genetical analysis of dormancy in rice seed.
The chemical determination by means of thin layer chromatographies showed that the main inhibitor was nearly undoubtedly abscisic acid (ABA) .
2. Auxin in dormant seeds was recognized only in both embryo and endosperm, and not in hull. Activity of auxin in endosperm was stronger than that of embryo, then it was cleared that the most of auxin in seed was contained in endosperm unlike inhibitors.
The chemical determination by means of paper chromatography showed that auxin contained in rice seed was probably 3-indoleacetic acid (IAA) .
