Resource acquisition and transport in plants — A/L Biology

What must I remember about Resource acquisition and transport in plants?

• Water potential (Ψw) is the free energy of water per unit volume, determined by solute potential (Ψs) and pressure potential (Ψp): Ψw = Ψs + Ψp; pure water has Ψw = 0 at standard temperature and pressure.
• Water and minerals move through roots via three distinct routes: Apoplast (along cell walls and intercellular spaces), Symplast (through cytoplasm connected by plasmodesmata), and Vacuolar pathway.
• The Casparian strip in endodermal cells contains suberin, blocking the apoplastic route and forcing water and ions through the selectively permeable plasma membrane into the vascular cylinder.
• Xylem sap ascent is driven primarily by Transpirational Pull explained by the Cohesion-Tension theory: water evaporation from mesophyll cells creates negative pressure (tension), transmitted through continuous water columns maintained by cohesive (H-bonds between water molecules) and adhesive (water to xylem wall) forces.
• Phloem translocation moves organic solutes (sucrose) from sources to sinks via the Pressure-Flow Hypothesis: active loading of sucrose into sieve tube elements lowers solute potential, drawing in water by osmosis to generate high turgor pressure that drives bulk flow.

Test yourself (1 minute)

1. Water potential gradient

   Water always moves spontaneously from a region of higher (less negative) water potential to lower (more negative) water potential.

2. Root pressure and guttation

   Under low transpiration and high soil moisture, root pressure pushes water droplets out through hydathodes at leaf margins (guttation), distinct from dew.

3. Stomatal opening mechanism

   Influx of K+ and Cl- ions into guard cells driven by proton-ATPase pumps lowers their water potential, causing water intake by osmosis, turgor increase, and pore opening due to radially oriented cellulose microfibrils.

Practise Resource acquisition and transport in plants questions today

Source: NIE G.C.E. (A/L) Biology Syllabus & Resource Book, Unit 4

What should I study first?

What comes next?

Next in the syllabus

Where does Resource acquisition and transport in plants fit in the syllabus?

Year 1 · Term 3