water movement through soil + plants

Question 1

water potential define

Answer 1

water potential ( ψ ) – the capacity of water to do work, amount of free energy in wate

Question 2

water potential describe

Answer 2

Pure water at soil surface has potential of zero
- Water potential is generally negative
- Water moves from soil to plant when ψ plant < ψ soil
- More stable at lower concentration
- Water movement into the soil depends on soil particle size and matric forces (adhesion+
cohesion

Question 3

what is water potential affected by?

Answer 3

pressure, osmotic potential, matric forces

Question 4

pressure potential

Answer 4

Pressure potential ( Ψp) – reduction in pressure potential generated by
evapotranspiration. Creates a water vapor pressure deficit and negative pressure is
exerted on water

Question 5

osmotic potential

Answer 5

Osmotic potential ( Ψs) – reduction in water potential due to dissolved solutes (harder
to pull water with salty water)

Question 6

matric forces?

Answer 6

Matric forces (Ψ m) – reduction in matric forces from absorption of water to surface of
plant cells or soil particles (water sticks to soil particles by size or texture makes it
harder to pull water out )

Question 7

rate of water movement through soil or plant

Answer 7

J s
J s = Ls * ∆Ψ/ I
Driving force -> ∆Ψ = water potential gradient
Resistance to movement -> Ls = hydraulic conductivity
I = path length

Question 8

what is hydraulic potential? affected by

Answer 8

Hydraulic conductivity – the capacity to conduct water
Affected by:
1. Soil texture
2. Flow through macropores (influenced by compaction, soil organisms, roots)
3. Xylem vessel diameter (species specific)

Question 9

enhance productivity by?

Answer 9

ncrease hydraulic (easier to move water) = rate of water increases
Sand – higher hydraulic conductivity
Clay – significant smaller hydraulic conductivity