ABSTRACT
Carbohydrate metabolism and its regulation are of central importance to the growth and development of plants. Cucurbits have long been considered ideal materials for carbohydrates metabolism studies for a number of reasons. First, the cucurbits synthesize and translocate assimilates mainly in the form of rafnose family oligosaccharides (RFOs). As a result, the loading, translocation, and unloading mechanisms in cucurbits are largely different from those in sucrose-translocating plants. Second, cucurbit fruits are relatively fast growing. Some types of pumpkins show maximum dry weight gain of 1.71 g h−1 during growth (Crafts and Lorenz, 1944). Recently (October 2014), a Swiss farmer claimed a new world record with a pumpkin weighing 953.5 kg. These evidences indicate that the mass transfer rate in cucurbit phloem is quite fast. Third, the long petioles and stem internodes and relatively abundant phloem sap exudation from the incised stem facilitate radiolabeling studies and sample collection and analysis.
