Which of the following is the most accurate comparison of the driving forces behind fluid movement in xylem versus phloem?
Understand the Problem
The question asks for the most accurate comparison of the driving forces behind fluid movement in xylem and phloem. It tests knowledge of how water and nutrients are transported in plants, specifically the mechanisms involved in xylem (water transport) and phloem (sugar transport).
Answer
Xylem uses transpiration (passive), while phloem uses active transport of sugars (energy required).
The driving force in xylem is transpiration, a passive process where water evaporates from leaves, creating tension. Phloem transport relies on active transport of sugars, requiring energy to move sucrose into sieve tube elements.
Answer for screen readers
The driving force in xylem is transpiration, a passive process where water evaporates from leaves, creating tension. Phloem transport relies on active transport of sugars, requiring energy to move sucrose into sieve tube elements.
More Information
Xylem and phloem are the vascular tissues in plants responsible for the transport of water, minerals, and sugars. Xylem primarily transports water and minerals from the roots to the rest of the plant, while phloem transports sugars (produced during photosynthesis) from source tissues (e.g., leaves) to sink tissues (e.g., roots, fruits).
Tips
A common mistake is thinking both xylem and phloem transport rely on the same mechanism (either both active or both passive). Remember that xylem transport is largely passive, driven by evaporation, while phloem transport requires energy to load sugars.
Sources
- Plant Transport Processes II - organismalbio.biosci.gatech.edu
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