Ion Transport

I. Root Anatomy

• Function
  • absorption
  • anchorage
  • storage
  • conduction of water
  • hormone synthesis
• Anatomy
  • three regions
    • meristematic
    • elongation
    • differentiation: root hairs
  • root hairs increase surface area
  • zone of depletion around root hairs
  • compsenatory growth in favorable soil environment

II. Ions in Soil

• movement of minerals to roots
• soil solution
• clay particles, cation exchange capacity
• Movement of ions
  • Root interception
    • root grows and intercepts ions
  • simple diffusion
    • concentration gradient
    • delivers K
  • mass flow
    • bulk flow of water carries ions to root
    • delivers N, Ca, Mg, S
  • mycorrhizal fungi
    • two types
    • endo
    • ecto
    • deliver P, Fe and other immobile nutrients
    • if added P to soil, inhibits fungal infection

III. Movement of ions into cells

• Diffusion
• Facilitated difffusion with a protein
  • know rate graph of facilitated difffusion and simple diffusion
• Active Transport
  • Movement of ions against gradient

IV. Active transport

• Voltage difference across a membrane
  • 100-300 mv difference
  • inside negative to outside of cell
• Nernst Equation
  • Predict how ions get in/out of cell
  • Log [ion]in/[ion]out = - (delta E (z)/ 59)
  • calculate predicted vs actual conc in cell given outside conc
• ATPase on Plasma membrane
  • pumps H+ ions out of cell
  • creates pH gradient
  • evidence (see handout)
• ATPase on vacuole membrane
  • vacuole less negative than cytoplasm
  • transport of ions into vacuole
• Types of transport
  • symport
  • antiport