Unloading of Sucrose at the Sinks

• Likely unloading of sucrose at sinks is also active transport by a reversed process, cells at the sink use sucrose, either for cell respiration or conversion to starch for storage
• Reduces sucrose concentration in sink cells and so, sucrose diffuses in from the sieve tubes; removal of sucrose from phloem sieve tubes increases water potential of phloem sap
• So water diffuses, by osmosis, from the phloem sieve tubes into sink cells and hydrostatic pressure in phloem sieve tubes at the sink decreases - required for continued mass flow