Transport in Plants
Water Transport
 = S + P

solute pressure
result of concentration of solute in a solution

pressure potential
hydrostatic pressure
Water Transport
water flows down a water potential gradient

water will move from solution with the higher (less negative) water potential to that with the lower (more negative) water potential
Mineral Uptake
requires facilitated diffusion or active transport proteins

proton pump
Ion Transport into Xylem
transported into the cortex

may move with water or via diffusion
Water Transport into Xylem
moves into the root and into the stele because each has a more negative water potential

aquaporins

passage via:
apoplast
symplast
Endodermis and Pericycle
endodermis is a selective barrier
Casparian strips

pericycle
transfer cells

Transpiration-cohesion-tension Mechanism
transpiration

tension

cohesion
Stomata
control rate of transpiration

guard cells
open and close in response to light and daily rhythms
active transport of H+ out
K+ diffuse down electrochemical gradient into guard cells
Pressure Flow Model
explains movement of phloem sap

source vs. sink


Pressure Flow Model
1. high solute concentration at source

2. increase in hydrostatic pressure

3. sugars in sink draw water out of phloem