Abstract
The second internode counted from the top of the rice culm, which is controlled by a single recessive gene (d1), is unable to elongate more than 5 mm under natural conditions. The elongation of this genetically shrunken internode was induced by high temperature given for one week after flower bud initiation, but not by low temperature. The shrunken internode showed anomalously high IAA oxidase activity as compared with the other internode in the mutant rice plant as well as the second internode in normal rice plants.
The high IAA oxidase activity was decreased by high temperature stress, but not by low temperature. The elongation of this genetically shrunken internode was associated with the decrease of IAA oxidase induced by high temperature. While the shrunken internode was elongated by the supply of 1, 000 ppm NAA solution. Therefore, it seems that there is an inharmonious relationship between auxin destruction and internode elongation in the mutant rice plant.
