Rice (Oryza sativa L.) life cycle and yield depend on the partitioning of assimilated carbon to ripening caryopses. Structural and functional aspects of this important process were investigated. First, spatiotemporal dynamics of ripening were assessed. Panicle fresh weight accumulation was maximum after three weeks and had a maximum rate after twelve days. Panicle architecture and ripening asynchrony were reduced to the form of an annotated panicle array. This format permitted a quantitative, computational approach to panicle consensus generation, data analysis and graphical display. Next, the separability of caryopsis tissues was assessed. The caryopsis coat was mechanically isolated from most of the embryonic tissues and facially separated into outer and inner coats from within the tube cell layer. Pectolyase Y-23 compromised adhesion between the maternal nucellus and embryonic aleurone and between endosperm cells. Viable protoplasts were prepared from approximately 10% of the isolated endosperm cells. Low protoplast yield was correlated with low viability of the isolated cells. Third, the mechanism of sucrose uptake by the aleurone was studied. The sucrose concentration-dependence of uptake rate had a nonsaturable component and a relatively small saturable component. Finally, electrophysiology of the caryopsis coat was assessed. Membrane potentials of the aleurone and nucellus were approximately -60 mV and -80 mV, respectively, and invariable over a range of bath conditions. Sucrose negligibly depolarized the aleurone membrane potential. Thus, it was not possible to confirm that the saturable sucrose influx was mediated by a cotransport system. Overall, the work has increased the experimental accessibility of ripening panicles and caryopses for research on the control of carbon partitioning.