Translocation (AQA GCSE Combined Science: Synergy: Life & Environmental Sciences): Revision Note

Translocation

The process of translocation

• The soluble products of photosynthesis are sugars (mainly sucrose) and amino acids

• These substances are transported in the phloem as cell sap

• This process is known as translocation

• Translocation occurs from sources (where substances are made) to sinks (where they are used or stored)

• Transport in the phloem can occur in different directions depending on the stage of development or time of year

  • During winter, sucrose and amino acids are transported from storage organs to other parts of the plant to allow respiration to continue

  • During growth periods, storage organs act as sources and growing tissues act as sinks

  • After growth, leaves act as the source and roots act as sinks, storing sucrose as starch

Structure of the phloem

• Phloem is made of living, elongated cells, unlike xylem which is made of dead cells

• Phloem cells are joined end to end

• The end cell walls contain sieve plates with pores that allow substances to flow between cells

• Phloem transports dissolved sugars from the leaves to the rest of the plant for use or storage

Translocation through the phloem moves cell sap from the leaves to other regions of the plant

Comparing the xylem and phloem