Chapter 36: Resource acquisition and transport in vascular plants Flashcards
What kind of molecules are plant primary cell walls composed of?
Cellulose
What is the purpose of the central
vacuole?
Reservoir, waste dump, storage
plasmodesmata
channels which traverse the cell walls of plant cells, enabling transport and communication between them
Apoptosis
Programmed cell death
Apoplastic route
through cell walls and extracellular spaces
Symplastic route
through the cytosol
Transmembrane route
across cell walls
Apoplast
everything external to the plasma membrane (cell
walls, extracellular spaces, and the interior of vessel elements and tracheids)
Symplast
the cytosol of living cells as well as the plasmodesmata
Diffusion
passive movement across the cell membrane (e.g., oxygen)
Osmosis
movement of water across the cell membrane
Facilitated diffusion
uses transport proteins and is a primary way that glucose is moved across the cell membrane
Active transport
moves atoms, ions, or molecules into or out of the cell (endocytosis and exocytosis are examples)
Electrochemical gradient
H+ ions and active transport drive solutes across the
cell membrane and against the concentration (e.g., transport of sucrose by phloem)
ATP-dependent proton pump moves solutes from…
Low to high concentrations
Water potential
combined effects of solute concentration and physical pressure upon water movement in plants
Turgor pressure
pressure exerted by the plasma membrane against the cell wall, and the cell wall against the protoplast
Protoplast
living part of the plant cell including the plasma membrane
What happens if you place a flaccid cell into a
sucrose solution?
Water moves out of the cell and the cell plasmolyzes aka loses water (thus, the water potential inside the cell is more negative)
What happens if you place a flaccid cell into pure
water?
Water moves into the cell and the cell becomes turgid (thus, the water potential inside the cell is 0)
Selective passage is directed by the…
Endodermis
Endodermis
innermost layer of the cortex that surrounds the vascular cylinder
The _____ blocks movement of water and solutes in the vascular tissue through the apoplastic route.
casparian strip
Transpiration
loss of water from stems and leaves to the surrounding air vapor by diffusion and evaporation
Transpirational pull
a force that works against the direction of gravity in plants
Spongy mesophyll
increases surface area for gas exchange but also increases the surface area for water loss (This layer is analogous to the alveoli in lungs)
Cohesion
linking together of like molecules due to hydrogen bonds
Adhesion
the clinging of water molecules to cellulose molecules by means of hydrogen bonds
Bulk flow
the process by which proteins with a sorting signal travel to and from different cellular compartments
How is bulk flow different from diffusion?
Faster
Moves entire solution
Occurs in hollow dead cells
Driven by pressure potential not solute potential
Cavitation
Water conduction can be interrupted when air bubbles form in the tracheids or vessel elements
How do plants control water loss?
Guard cells
Which is narrower: tracheids or vessel elements?
Tracheids
Turgor pressure (opening and closing) is regulated by uptake and loss of _____ ions by the guard cells
Potassium
Light ____ K+
Increases
CO2 depletion _____ K+
Decreases
Circadian rhythm
24 hour cycle (internal clock)
Xerophyte
a plant that lives under arid conditions
Adaptations for Water Conservation
- small, thick leaves
- very thick, waxy cuticle
- hairs (trichomes) on leaves or recessed stomata
- drought deciduousness
- CAM photosynthesis
- Well-defended against herbivores (e.g., spines, toxic chemicals)
CAM photosynthesis
a carbon fixation pathway that evolved in some plants as an adaptation to arid conditions that allows a plant to photosynthesize during the day, but only exchange gases at night
Phloem is transported from a ______ to
a _______.
sugar source, sugar sink
Sugar source
a plant organ that is a net producer of sugar by photosynthesis or by breakdown of starch
Sugar sink
a plant organ that is a net consumer or depository of sugar
Translocation
Phloem transports the products of photosynthesis
Conduit cells for translocation
sieve-tube elements
companion cells
located alongside sieve-tube elements but do not conduct phloem sap
can aid in loading and unloading of sugars from sieve-tube elements
Xylem > transpiration >
Negative pressure
Phloem > translocation >
Positive pressure
What causes phloem to flow from the source to the sink?
Pressure flow
