Abstract
Root growth in rice seedlings was measured using a bi-layered agar medium, the upper half of which was nitrate free and the lower half of which contained different concentrations of nitrate. When the primary root grew up to approximately 15 mm in length, each germinated seed was transferred to a glass tube containing the bi-layered medium and cultivated at 25℃ under continuous lighting. In the japonica rice cultivars, Nipponbare and Kinmaze, the relative growth rate (RGR) of primary roots was highest between the first and second days after transplanting and gradually decreased. Although nitrate concentration had no effect on RGR in either cultivars, the bi-layered medium presented in this experiment would be useful for detecting nitrate sensing in roots, as change in root growth and proliferation of secondary roots were easily detected.
