Resource Acquisition And Transport In Vascular Plants Flashcards
What is light capture determined by?
Canopy structure and phyllotaxy
Canopy structure
How many leaves are there; more leaves=more light absorbed
Phyllotaxy
Arrangement of leaves; no leaves covering each other=more light absorbed
What is nutrient acquisition determined by?
Root structure, proliferation of high nutrient zones, and symbiotic associations w/ mycorrhizal fungi
Apoplastic route
Moves through matrix of cell walls and intercellular space of cortex; passively moving; not passing through cell membranes
Symplastic route
Moves through cells via plasmodesmata
Transmembrane route
Combination of apoplastic and symplastic; ions move across membrane to leave cell then transported into another part of cell
Casparian strip
Waxy layer that prevents anything from entering via apoplastic route
What changes do water and nutrients have to do to reach the vascular cylinder?
Go from apoplastic to symplastic
Passive transport
Diffusion across a membrane
Active transport
Pumping of solutes across a membrane using ATP
Aquaporins
Water channel proteins
Osmosis
Determines the net absorption or loss of water by a cell
Water potential
A measurement that combines the effects of solute concentration and pressure
Transpiration
Evaporation of water from a plants surface; plants lose a large volume of water because of this
What replaces the water lost via transpiration?
The water gained by bulk flow called xylem sap
How does the sap rise and is it pulled?
Water moves in via roots because they adjust its osmotic potential (-) so water can move in
Xylem tissue cannot adjust b/c dead, but water is being moved up because of the negative pressure caused by a vacuum (created by water being pulled from the top but not being replenished fast enough)
Water moves up to the leaves b/c they modify their water potential by affecting the osmotic component
Water is pulled out of the plant because of the dry air’s high negative pressure
Which direction does water flow?
Regions of high water potential to regions of low water potential
What unit is water potential?
Megapascals
Solute potential
Also called osmotic potential; is proportional to # of dissolved molecules; more solutes=more negative
Pressure potential
Physical pressure on a solution
What helps move the water up the xylem in the trunk?
Adhesion w/ cell wall and cohesion w/ other water molecules
How do guard cells open stoma?
H+ ions are pumped out, K+ ions move in -> low osmotic/solute potential, water moves in; slow process; guard cells are turgid
How do guard cells close stoma
H+ pumped in, K+ leaves , higher osmotic/solute potential, water moves in; quicker process; guard cells are flaccid
How does wilt happen?
If lost water is not replaced by transport of water
Name a reason why transpiration can be good.
Results in evaporative cooling, lowering temp. of plant and preventing denaturing of enzymes
Phloem sap
Aqueous solution that is high in sucrose and is transported to a sugar sink via diffusion or bulk transport
Sugar source
Organ that is a net producer of sugar like mature leaves
Sugar sink
Organ that is a net consumer or storer of sugar, like a bulb or tuber
Companion cell
Supports the sieve tube element and transfers/modifies sugars
Sieve tube element
Disperses sugar through plant and the sugar is then consumed at sugar sinks
How does sap move through a sieve tube?
Sugar is loaded into phloem
Since sugar is going into the phloem from the xylem there is a low osmotic potential. This causes phloem to swell.
Sugar then leaves phloem into sinks which increase osmotic potential and water moves from phloem back to xylem.
Water is recylced
