9.4 Translocation

Translocation

Energy-Requiring (active) process transporting assimilates, particularly sucrose between the sources (e.g. leaves) and sinks (e.g. roots, meristem)

Sources

• Green leaves and stems

• Storage organs (tubers, tap roots)

  • Unload their stores at beginning of growth period

• Food stores in seeds when they germinate

Sinks

• Roots that are growing and/or actively absorbing mineral ions

• Meristems that are actively dividing

• Any parts of the plan that are laying down food stores e.g. developing seeds, fruits, or storage organs

Why is sucrose the main carb transported rather than glucose?

Not used in metabolism as readily as glucose so is therefore less likely to be metabolized during transport process

Phloem loading - Symplast route

• Passive route

• Sucrose ends up in sieve elements & water follows by osmosis

• Creates a pressure of water that moves sucrose thru phloem by mass flow