During post-phloem unloading, sucrose enters the apoplast of the rice endosperm after it is released from the cells of the nucellus. Subsequent starch synthesis and accumulation in the endosperm requires that sucrose be transported across the plasma membranes of starchy endosperm cells or aleurone cells. We have isolated and purified protoplasts from the aleurone layer of ten-day-old rice caryopses. Caryopses were peeled to expose the aleurone layer. The middle lamellas were digested with pectolyase and the aleurone cells released by gentle sheering. Digestion of the cell walls with cellulase isolated protoplasts that were then purified by Percoll density-gradient centrifugation. Radiotracer and silicone oil centrifugation techniques are being used to study the kinetics of sucrose uptake by these protoplasts.

Key words: aleurone, carbon partitioning, rice, sucrose transport