COMPARISON OF ROOT SYSTEMS AMONG RICE CUL TIVARS BY SIMPLIFIED INVESTIGATION METHODS

Simplified investigation methods of root systems in Japanese and Ameri can rice cultivars were examined using photographic recording methods and image analysis on a personal computer. In order to photograph flat expanded root systems, plastic boards were inserted vertically into t he soil and culture boxes before seeding or planting in each experimen t. Each root system profile picture was divided into parts every 5cm f rom the plant and at an angle of 22.5 degrees from the horizonal. The 'center of root system gravity' [CRSG:integrated (PV x RPA)/the sum of RPA)] and 'moment of root system' [MRS:integrated (PV x RPA)] were ca lculated as indicators of root distribution using the 'position value' (PV:the distance x the angle) and the 'root projection area' (RPA) in each part. In field experiments, cultivar differences in root system profiles were revealed easily, and all American cultivars except New b onnet showed a tendency of deep distribution and large root quantity ( CRSG:Lemont>New bonnet greater than or equal to M-401>M-7 greater than or equal to Ishikari>Nipponbare>Tsukinohikari greater than or equal t o Nakateshinsenbon, MRS:M-401>M-7>Lemont greater than or equal to Nipp onbare>Nakateshinsenbon greater than or equal to Tsukinohikari greater than or equal to New bonnet greater than or equal to Ishikari). In la rge root box experiments, it was possible to obtain the values of CRSG and MRS similar to those obtained in the field experiments; however, it was difficult to evaluate numerous cultivars owing to the high cost of root boxes and troublesome management. In small plastic root boxes and water culture experiments, it was not possible to obtain accurate values for them.