Phloem Unloading

Phloem unloading is essentially the reverse process at the far, receiving end of translocation, moving sucrose out of the sieve elements and into a sink organ such as a root, tuber, flower or fruit, and it likewise proceeds in three steps. First, in sieve element unloading, sucrose actually leaves the sieve tube itself. Second, in a short-distance transport step, this sucrose moves onward into the cells of the sink tissue proper. Third, and finally, in storage and metabolism, the delivered sugar is either converted into an insoluble storage form or is directly consumed by the sink cells to f …