Chapter 5 · Question 17
How is food transported in plants?
Q17
How is food transported in plants?
Answer Revealed
Direct Answer:
Food (sucrose) is transported from leaves to all plant parts through phloem sieve tubes using energy from ATP (translocation).
Simple Explanation
Food made in the leaves travels through special tubes called phloem to reach every part of the plant — roots, stems, fruits, and growing tips. This movement uses energy.
Exam-Ready Structure
Food synthesised in leaves (mainly sucrose and amino acids) is transported to all non-photosynthetic parts of the plant through the phloem tissue. This process is called translocation. The mechanism involves: 1. At the source (leaves), sucrose is actively loaded into phloem sieve tubes using ATP energy. This increases the osmotic concentration inside the phloem. 2. Water from adjacent xylem enters the phloem by osmosis, creating high pressure at the source. 3. At the sink (roots, fruits, growing regions), sucrose is actively unloaded from the phloem, lowering the osmotic pressure, which allows water to exit. 4. The pressure difference between source and sink drives the bulk flow of phloem sap from source to sink. This is called the pressure-flow or mass-flow hypothesis.
Key Points
- Food moves from leaves (source) to other parts (sink)
- Phloem transports food bidirectionally
- Translocation requires energy (ATP)
- Pressure gradient drives the flow
Common Mistakes
- Saying phloem transports only upward
- Confusing phloem transport with xylem transport
Relevant Maps and Figures
Movement of Water During Transpiration
diagram
Use the plant transport visual to contrast xylem water flow with food movement in phloem.
The figure is most helpful when explaining that phloem transport uses energy.
Use this tree transport diagram to explain upward movement through xylem and to contrast transpiration pull with food movement in phloem.
Answer Sources
- Translocation in phloemtextbook section | Science | Life Processes | Transport of food in plants | Pages 17-18