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Flashcards in Plant Transport Deck (20):

Components of water potential

total potential = solute potential + pressure potential


Movement of water

Passive movement toward more negative total water potential


Hypotonic solution for plants

Turgid cell (normal)


Isotonic solution for plants

Flaccid cell (limp)


Hypertonic solution for plants

Plasmolyzed cell


Solutes' effect on potential

Negative effect
Binding of water molecules


Positive pressure's effect on potential

Positive effect
Pushing water


Solutes' and positive pressure's effects on water movement

Opposing effects on water movement (net 0)


Negative pressure (tension)'s effect on potential

Negative effect
Pulling water


Movement of water into cell

Water goes into cell until cell potential=solution potential


Passive transportation

No energy required
Movement from high to low concentration
Simple diffusion
Facilitated diffusion: channel (charged molecules) or carrier (binds specific molecule)


Active transportation

Energy required
Movement from high to low concentration
Primary active: transport directly coupled to ATP
Secondary active: solute transported using potential energy from chemiosmosis (H+ gradient)


Positive ions moving out of cell (membrane is positively charged)

Can be done if the concentration gradient is greater than the charge differential


Structural aspects of stomata

Guard cells attached to each other at their ends
Radially oriented microfibrils- more support on inside of cell than outside


Mechanism of water movement in stomata

Pumping K+ in or out of the guard cell changes solute potential and total potential
Osmosis due to potential differences
Guard cells swell or go limp, opening or closing stomata


Short distance transport

Diffusion: 3 routes
Apoplastic route (non-living parts, within cell walls)
Symplastic route (living parts, within cytoplasm)
Transmembrane route


Casparian strip

Links endodermal cells in plants
Prevents passage of cations and most solutes into endodermis


Transport of sucrose in plant cells

Mesophyll cell -> bundle-sheath cell -> phloem parenchyma cell OR companion cell (through cell wall)-> sieve tube element -> phloem parenchyma cell
Sucrose is cotransported against its concentration gradient with H+ from the cell wall space into the sieve tube cell


Transport of sucrose from source cell (leaf) to sink cell (root)

Loading of sugar from source cell (leaf) into sieve tube (phloem)
Uptake of water: osmosis from xylem (water pressure moves sucrose from high pressure to low pressure)
Unloading of sugar from sieve tube into sink cell (storage root)
Water recycled back into xylem


Cohesion-tension theory

Long distance transport in xylem: water molecules cohere to each other and adhere to the xylem walls, overcoming gravity
Works by tension (negative pressure): much lower potential at top than at bottom
Too much tension: cavitation (air bubble)