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Difficulty: MediumTransport Mechanisms in Plants

Match each plant transport process or pathway on the left with its corresponding physiological mechanism or structural feature on the right.

  • Long-distance upward xylem transport in tall treesTranspiration pull coupled with cohesive and adhesive forces
  • Symplastic movement of water across root cortexCell-to-cell diffusion through microscopic plasmodesmata
  • Phloem translocation of organic assimilatesHydrostatic pressure gradient generated by osmotic loading
  • Development of positive root pressureActive solute accumulation in xylem vessels lowering water potential

Answer

Long-distance upward xylem transport matches transpiration pull coupled with cohesive and adhesive forces; Symplastic movement of water matches cell-to-cell diffusion through microscopic plasmodesmata; Phloem translocation of organic assimilates matches hydrostatic pressure gradient generated by osmotic loading; Development of positive root pressure matches active solute accumulation in xylem vessels lowering water potential.
Each transport process pairs precisely with its core mechanism: xylem sap ascent requires transpiration pull and cohesion-tension; symplastic water transfer proceeds through living protoplasm via plasmodesmata; phloem assimilate transport operates under osmotic pressure-flow gradients; and root pressure develops through active mineral accumulation in root xylem.

Step-by-Step Solution

1
Identify the primary mechanism driving long-distance water movement in xylem.
Correlate xylem sap movement with the cohesion-tension theory and transpiration pull.
Evaporation of water vapor from leaf mesophyll cells generates a negative pressure potential (tension) that pulls a continuous water column upward.
2
Differentiate between apoplastic and symplastic water pathways across root tissues.
Connect symplastic transport with movement through cytoplasm and plasmodesmata.
While the apoplast pathway moves water along porous cell walls, the symplast pathway progresses through living cell interiors connected by plasmodesmata.
3
Analyze the driving force behind assimilate movement in phloem sieve tubes.
Associate phloem translocation with the pressure-flow hypothesis.
Active transport of sucrose into sieve tubes draws water osmotically from xylem, building hydrostatic pressure that pushes sap toward sink organs.
4
Determine the origin of positive pressure recorded in root xylem exudation and guttation.
Relate root pressure to active mineral uptake and osmotic water influx.
Active secretion of inorganic ions into root xylem vessels lowers xylem solute potential, creating osmotic pressure that forces sap upward.

Key Concept

Mechanisms and structural pathways governing water, mineral, and organic solute transport in vascular plants
Estimated Time:1m 30s
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Topics

Transport Mechanisms in Plants

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