| Abstract: | The long-distance transport of sugars has been investigatedin cucurbits. 14C-labelled sugars were applied to an abradedleaf surface and the content of 14C in various fractions ofextracts from leaf blade, petiolar tissue, and phloem exudatesubsequently determined. Nearly one half of the 14C activitydetermined in the phloem sap was in amino and organic acids,the other half in sugars, whereas in leaf and petiolar tissuemost of the 14C activity was found in the neutral sugar fraction.As the solute concentration of cucurbit phloem sap is relativelylow the calculated rate of mass transfer would require hightransport velocities and large areas of phloem. However, thedriving force for such translocation is not known. Key words: Phloem transport, Cucurbits, Specific mass transfer |
