Study Notes
Transport in the phloem involves the movement of organic compounds from sources, where they are synthesized, to sinks, where they are used or stored. This process is driven by pressure and water potential differences in the phloem.
- Translocation — the movement of organic compounds from sources to sinks. Example: Sugars move from leaves (source) to roots (sink).
- Source — the site where organic compounds are synthesized. Example: Leaves are a common source.
- Sink — the site where organic compounds are delivered for use or storage. Example: Roots and fruits are typical sinks.
- Phloem — the vascular tissue responsible for the transport of organic compounds. Example: Phloem transports sucrose from leaves to roots.
- Sucrose — a disaccharide transported in the phloem. Example: Sucrose is soluble and metabolically inert, making it ideal for transport.
- Hydrostatic pressure — pressure that builds up in the phloem due to water incompressibility. Example: High pressure at the source pushes sap towards the sink.
Exam Tips
Key Definitions to Remember
- Translocation: Movement of organic compounds from source to sink.
- Source: Site of synthesis of organic compounds.
- Sink: Site of use or storage of organic compounds.
- Phloem: Vascular tissue for transporting organic compounds.
Common Confusions
- Confusing xylem and phloem functions.
- Misunderstanding the role of hydrostatic pressure in phloem transport.
Typical Exam Questions
- What is translocation? Movement of organic compounds from source to sink.
- How does sucrose move in the phloem? Sucrose moves from high pressure at the source to low pressure at the sink.
- What role does water play in phloem transport? Water creates hydrostatic pressure that drives the flow of sap.
What Examiners Usually Test
- Understanding of source and sink dynamics.
- Mechanism of pressure flow in phloem.
- Ability to identify phloem in microscope images.