Transport of Sugar

Rucete ✏ Biology In a Nutshell

1. What Is Translocation?

• Translocation is the process of transporting carbohydrates (mainly sucrose) through the phloem from a source (e.g., leaves) to a sink (e.g., roots, fruits, or growing tissues).
• This movement ensures that energy-rich sugars produced by photosynthesis are delivered to parts of the plant that require them for growth, storage, or metabolism.

2. Source and Sink Dynamics

• Source: A plant organ that produces or releases sugar, typically the leaves.
• Sink: A part of the plant that consumes or stores sugar, such as roots, fruits, seeds, or actively growing tissues.

3. Mechanism: Pressure-Flow Hypothesis

1. Loading of sugar into the phloem at the source creates a high solute concentration.
2. Water enters the phloem by osmosis, generating high turgor pressure.
3. This pressure causes sugar-rich sap to flow through the phloem toward areas of lower pressure (the sinks).
4. Unloading of sugar at the sink reduces solute concentration and water exits, completing the cycle.