Temporal and Spatial Regulation of Sucrose Accumulation in the Sugarcane Stem

Sucrose accumulation has been studied extensively in sugarcane-an example of a highly productive crop plant with the capacity for storing large quantities of sugar. Initial recognition and characterisation of the enzymes involved in sucrose synthesis and cleavage led to widely accepted models of how sucrose transport and accumulation occur. Studies on cells in culture and on isolated cellular fragments initially supported and strengthened these models but more recently have revealed weaknesses in them. Biophysical measurements and anatomical, histochemical, and tracer dye studies further eroded the older models. Molecular studies are beginning to reveal details at the gene and transcriptional levels of the enzymes involved in sucrose transport and metabolism. Collectively, results of recent research indicate the need for a new sucrose accumulation model. A dynamic model of rapid cycling and turnover of sucrose between the vacuole and metabolic and apoplastic compartments explains much of the data, but details of how the cycling is regulated remains to be discovered.