Transport in Plants — Translocation

This lesson covers the role of phloem in transporting dissolved sugars (and other organic substances) around a plant — a process called translocation — as required by the Edexcel GCSE Combined Science specification (1SC0). You need to understand the differences between xylem and phloem, what is meant by source and sink, and how translocation works.

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What Is Translocation?

Translocation is the movement of dissolved sugars (mainly sucrose) and amino acids through the phloem from where they are made or stored (sources) to where they are needed (sinks).

Unlike the transpiration stream in xylem, translocation can move substances in both directions — upward or downward — depending on where the source and sink are located.

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Phloem Structure

Phloem tissue is made up of two main cell types: