Transcript Lab #9 Transpiration Lecture
Intro to Lab #9 / Chpt. 36 Plant Structure and Transport
pg. 744 - 753
QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
Transport in Plants
average size maple tree looses 200 L of water per hour during the summer
this water were not replaced by the roots???
Question ?
•
How do plants move materials from one organ to the other ?
TRANSPIRATION
TRANSPIRATION
when a plant looses water vapor from the inside of the leaf, to the outside environment -via. stomata
COHESION - TENSION THEORY
water is pulled up from roots to leaves via. higher
in the leaf to a lower in the
Water & mineral absorption to Xylem: • Water absorption from soil osmosis - aquaporins
ROOT HAIRS = increase surface area for the absorption of water & minerals QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
Water & mineral absorption to Xylem: Mineral absorption – active transport – proton pumps • active transport of H +
proton pumps
Water & mineral absorption to Xylem: • Proton pumps – active transport of H + • chemiosmosis • H + gradient – creates membrane potential • difference in charge • drives cation uptake – creates gradient • cotransport of other solutes against their gradient ions out of cell
proton pumps
Transport in
cells: The survival of plant cells depends on the ability to balance the uptake & loss of H 2 O
Remember this?
*Presence of the cell wall adds physical pressure , this affects movement into the cell negatively!
Remember this?
* Solute concentration also affects movement:
Transport in Plants
direction of osmosis when a plant cell is surrounded by a solution???
Transport in Plants
Remember this?
Water moves from the solution of higher water potential, to a solution of lower water potential.
For plants, it is not just enough to know solution hypertonic.
if is the extracellular hypotonic or
Remember this?
*Measured in MEGAPASCALS
• Has two components: –Pressure potential : y r –Solute potential : y p y = y r + y p
Remember this?
You have to know these two numbers first, when determining water potential.
You must know water potential in order to know which direction water will move!
Pressure potential y r y p : Solute potential : y = y r + y p
Remember this?
Remember this?
any solution will have a negative w.p. adding solutes, lowers w.p.
Transport in Plants
*Solute concentration affects movement
Transport in Plants
solution counters its tendency to take up water due to the presence of solutes
Transport in
=
+ P
S
=
Transport in
moves water across the membranes of plant cells
COHESION - TENSION THEORY -
water is “pulled” b/c of it’s cohesive property
Evolutionary advantage of ROOT HAIRS: add surface area thus increasing amount of H 2 0/mineral solution coming into the plant!!
Mycorrhizae increase absorption
• Symbiotic relationship between fungi & plant – symbiotic fungi greatly increases surface area for absorption of water & minerals – increases volume of soil reached to plant – increases transport to host plant
Mycorrhizae
COHESION - TENSION THEORY -
Because higher water potential outside
COHESION TENSION THEORY -
minerals absorbed from soil into root~ creates
“root pressure ”
that pushes H 2 O/soil solution into xylem
COHESION - TENSION
QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
THEORY -
• uptake of soil solution by root hairs to
apoplastic route
through the cell walls
Transport routes in plant cells QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
COHESION - TENSION
QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
THEORY -
• uptake of minerals & water by root hairs to
symplastic route - through plasmodesmata
Transport routes in plant cells QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
Controlling the route of water in root • Endodermis – cell layer surrounding vascular cylinder of root – lined with impermeable Casparian strip – forces fluid through selective cell membrane • filtered & forced into xylem cells
QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
Controlling the route of water in root QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
• some soil solution from apoplast route, diffuses into the
symplastic route
-through the plasma membrane
COHESIO N TENSION THEORY
Water then travels thru the
-
root where the
Casparian strip
forces H 2 O into the xylem
REMEMBER: the
casparian strip
blocks water from entering via. The apoplastic route
COHESION - TENSION
QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
THEORY
-
• only minerals in the symplastic route can detour around the Casparian Strip AND
PASS INTO THE VASCULAR XYLEM!!
eudicot
Root anatomy
monocot
COHESION - TENSION
QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
THEORY
•
-
XYLEM vessels transport water and minerals upward into the shoot system (stem and veins)
COHESION - TENSION THEORY -
problem… this can only take the water “so far”
COHESIO N TENSION THEORY -
At the leaf of the plant, water loss due to evaporation is taking place.
Evaporating H 2 O decreases the water potential of the leaf.
Since water flows from higher water potential to lower, the water is pulled up the xylem with the minerals.
Transport of sugars in phloem • Loading of sucrose into phloem – flow through cells via plasmodesmata – proton pumps create energy potential/proton gradient • cotransport of sucrose into cells down proton gradient
Pressure flow in phloem • Mass flow hypothesis – “ source to sink ” flow • direction of transport in phloem is dependent on plant’s needs –
phloem loading
• active transport into phloem of sucrose • increased sucrose concentration decreases H 2 O potential – water flows in from xylem cells • increase in pressure due to increase in H 2 O causes flow
can flow 1m/hr
Maple sugaring
H 2 O
Transport in
CO 2
Transport in
CO 2 H 2 O How do environmental influences effect?
Transport in
flacid
Plants
Environmental factors influence this rate…