Water Relations Flashcards
Primary root
First organ to originatebfrom seed embryo
Secondary roots
Lateral roots
=> further anchoring
=> & uptake of water and nutrients
3 steps of water uptake
Uptake
Transport
Transpiration
Water
Polar solvent
=> mean of transport for solute
Medium and partner for biochemical reactions
Property of
Cohesion => attraction btw molecules => transpiration column
Adhesion => attraction to surface
Enables
Turgor: Stature & Growth
Temp regulation
Yield
Diffusion
Movement from subst. from high to low conc.
=> 2nd law of thermodynamics => stabilize env.
Diffusion (equations)
1st Fick’s law
Diffusion rate is proportional to concentration gradient
2nd Fick’s law
Diffusion time is proportional to square diffusion distance
Efficiency of Diffusion
Only in short distance
=> in large distances: additional force => Bulk flow
Bulk flow
Concerted movement of molecules en masse most often in response to a pressure gradient
Poiseuille’s equation
Volume flow rate depends on radius of vessel
Osmosis
Diffusion of water through semipermeable membrane
Osmotic potential
-RTc (c= osmolarity mol/L)
Pure water => psi (osmotic potential) is 0
Dilution of sth in water = reduction of psi
Water potential
Psi w = psi s + psi p + (psi g)
s = osmotic pressure
p = hydrostatic pressure (+ = turgor, - = tension (as in xylem))
Water flows
Passively (through osmosis) to area of lower psi
Deplasmolyse
Turgor
Pressure potential > 0
Plasmolyse
Pressure pot = 0
soil composition
Small particles enable vertical movement => better retention of water
Wilting point and field capacity
Point at which plants wilt and don’t recover and level above which soil can not take up more water
Determined by soil composition