Shift of the major sink from the culm to the panicle at the early stage of grain filling in rice (oryza sativa l. cv. sasanishiki)

To elucidate the precise process of distribution and redistribution of carbon assimilated at the early stage of ripening in rice plants, ¹³CO₂ was fed to the plants at the late booting, flowering, and beginning of milky stages in a phytotron under a constant environment, and the distribution and redistribution of the labeled carbon into the constituent organs were traced until the doughy stage. The most remarkable change in the carbon distribution and redistribution was observed at the beginning of the milky stage (around 10 d after heading). At this stage, the major sink changed from the calm to the panicle, and the culm became an exporter of accumulated carbon, while the leaf sheath continued to act as a carbon exporter from heading through early ripening.