Accumulation of 14C-labelled Carbohydrate Before Flowering and its Subsequent Redistribution and Respiration in the Rice Plant

Abstract

Rice plants (Oryza sativa L., variety IR8) were grown in the field at the International Rice Research Institute, Philippines in the dry season 1970. Ten days before flowering 200μCi of 14CO2 were fed to groups of four plants. At flowering, 7 days after flowering, and at maturity, the activity of 14C was determined. The activity of 14C present in starch and suger was determined at flowering and at maturity. Respiration of 14CO2 was measured in the field six times between flowering and harvest. The loss in 14C activity in the carbohydrate fraction was less than the 14C respiration, indicating that some respired 14CO2 were re-assimilated by the plant. The overall efficiency of translocation of 14C from the vegetative parts to the panicle was 79%. The noncarbohydrate fraction apparently was translocated without loss. The efficiency of carbohydrate translocation was 68% and 77% with and without taking into account the re-assimilation of 14CO2, respectively. With a translocation efficiency of 68 to 77%, the contribution of stored carbohydrate to grain carbohydrate is 24 to 27%, which is equivalent to 1.9 to 2.1t/ha of rough rice at 14% moisture. © 1972, CROP SCIENCE SOCIETY OF JAPAN. All rights reserved.