Mass flow hypothesis is the accepted mechanism used. for the translocation of sugars from source to sink glucose is prepared at the source by photosynthesis. The sucrose out of the phloem SAP and into the cells which will use the sugar converting. Translocation occurs within a series of cells known as the phloem pathway, or phloem transport system, with phloem being the principal food-conducting tissue in vascular plants. Nutrients are translocated in the phloem as solutes in a solution called phloem sap. Some argue that mass flow is a passive process while sieve tube vessels are supported by companion cells. Hence, the hypothesis neglects the living nature of phloem.