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77 terms

Chapter 38 Transport in Plants

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to outlaw; to condemn as dangerous; to interdict
Water first enters the _______ and then moves to the ______.
Roots; xylem
What is the innermost vascular tissue?
xylem
Water rises through the xylem because of ______________.
A combination of factors
Some of the water exits through the __________.
Stomata in the leaves.
What are the two types of transport mechanisms?
Short-distance movement and long-distance movement
What is short-distance movement?
Movement of water at the cellular level plays a major role in bulk water transport. Water can diffuse through cell membranes. However, ions and organic compounds rely on membrane-bound transporters. These are active or passive mechanisms.
What are long-distance movement?
Some "pushing" from pressure of water entering roots is involved. However, most of the force is "pulling." This is caused by transpiration.
What is transpiration?
Evaporation of water from the stomata
What is cohesion?
Water molecules stick to each other
What is adhesion?
Water molecules stick to walls of vessels
_______ are a way to represent free energy or "potential to do work"
Potentials
What is water potential used to predict?
which way water will move
high--------->low
What is water potential measured in?
units of pressure called megapascals (MPa)
What is osmosis?
Diffusion of water across a semi-permeable membrane
What will happen if a plant is placed in a solution with high water potential (low osmotic concentration)?
Cell will become swollen or turgid
What will happen if a plant is placed in a solution with low water potential (high osmotic concentration)?
Cell will exhibit shrinkage or plasmolysis
What is pressure potential?
turgor pressure against the cell wall
As turgor pressure increases, what happens to pressure potential?
Pressure potential increases
What is solute potential?
Pressure arising from presence of solute in a solution
As solute concentration increases, what happens to solute potential?
Solute potential decreases
What is the formula for water potential?
See slide 10
____________________
When a cell is placed in pure water, water will do what?
Move into the cell because water potential of cell is relatively negative
When a cell is placed in a solution with a different solute potential, what will happen to the water?
It will move in the direction that eventually result in equilibrium.
What is equilibrium?
When both cell and solution have the same water potential.
What are the signs for ...
water potential
pressure potential
solute potential
See slides 8 and 10
_______________________
_______________________
_______________________
What are aquaporins and what do they do?
Water channels in vacuole and cell membranes that speed up osmosis without changing direction of water movement
Water potential regulates movement of water through ___________.
The whole plant
Water will move from _____ into ______ if soil's water potential is greater. It will then move along gradients of successively more negative water potentials in _______, _______, and _____.
soil; roots
stems; leaves; air
Evaporation of water in a leaf creates ______ pressure or tension in xylem.
negative
What will a "negative water potential" do to the water?
Pull it up stem from roots
The gradient in vapor pressure is driving force for ________.
Transpiration
Most of water absorbed by plants comes in through ________.
Root hairs
What are the purposes of root hairs?
They collectively provide enormous surface area and almost always turgid because water potential is greater than that of soil.
An ________ is required for ions to accumulate in root cells.
expenditure of energy
On the roots, _____ are transported throughout the plant via the xylem.
ions
Surface area for water and mineral absorption is further increased by ___________.
Mycorrhizal fung
Mycorrhizal fungi are particularly helpful in the uptake of what?
phosphorus
What are the three transport routes that exist through cells?
Apoplast route
Symplast route
Transmembrane route
This route is the movement through cell walls and spaces between the cells
apoplast route
This route is sytoplasm continuum between cells connected by plasmodesmata
Symplast route
This route is membrane transport between cells and accross membranes of vacuoles within cells
Transmembrane route
Which route permits the greatest control?
Transmembrane route
Eventually on their journey inward, ______ reach the endodermis. Any further passage through the cell walls is blocked by the ________. Molecules must pass through ________ and ________ cells to reach xylem.
molecules;
Casparian strips;
cell membranes and protoplasts of endodermal cells
Root pressure is caused by what?
Continous accumulation of ions in roots. This causes water to move into plan and up the xylem, even without transpiration.
What is guttation?
the loss of water from leaves when root pressure is high
Root pressure alone, however, is insufficient to explain xylem transport. ______ provides main force.
Transpiration
Water has an inherent tensile strength due to ______ of its molecules.
Cohesion
______ of a water column varies inversely with diameter. This is because tracheids and vessels have strong cohesive water forces due to small diameter.
Tensile strength
Long column of water is further stabilized by ________.
Adhesive forces
______ can break the tensile strength of a water column.
Air bubbles
Air bubbles can expand and block the tracheid or vessel, causing an _______ or ________. Damage can be minimized by anatomical adaptations.
embolism or cavitation
_______ and _______ are essential for bulk transport of minerals.
Tracheids and vessels
________ are relocated through xylem from roots to active parts of the plant. What are some examples?
Minerals; phosphorus, potassium, nitrogen, iron, and calcium
Over ____ of water taken in by roots is lost to the atmosphere.
90 %
Photosynthesis requires ____ from the atmosphere.
CO2
Closing ______ can control water loss on a short-term basis. However, ________ open to allow CO2 entry.
stomata;stomata
_______ cells have thicker inner cell walls and thinner outer cell walls. This causes them to bulge and bow outward when turgid, which opens the stomata.
Guard cells
Turgor in guard cells results from active uptake of _______, _________, and _________.
potassium, chloride, and malate
Transpiration rates and evaporation rates increase with ________ and ________ velocity.
temperature and wind
_______ initiates signaling pathway to close stomata in drought stress. This opens the potassium, chloride, and malate channels and water lose follows.
Abscisic acid (ABA)
Stomata close at _____ temperatures and _____ concentrations.
high; high
Stomata open when blue wavelengths of light promote uptake of potassium by _______.
Guard cells
Alternative photosynthetic pathways, such as ___________, reduce transpiration
(CAM)
________ allow plants to limit water loss in drought conditions.
Morphological adaptations
Examples of morphological adaptations
dormancy; loss of leaves; covering leaves with cuticle and wooly trichomes; reducing number of stomata; stomata recessed in pits on leaf surface
Plants have adapted to flood conditions that _________.
Deplete avaliable oxygen
Plants in fresh water....
form aerenchyma, loose parenchymal tissue with large air spaces. collect oxygen and transport 02 to submerged parts
Plants, such as mangroves, that grow in salt water produce ________.
Pneumatophores
What are pneumatophores?
Spongy, air-filled roots, that emerge above mud. Have large lenticels for oxygen entrance. They also secret large quantities of salt
Plants called ______ live in saline soils. They produce high concentrations of organic molecules in roots. This decreases water potential enhancing water uptake from soil.
Halophytes
Most _______ produced in leaves are distributed in phloem to rest of the plant.
Carbohydrates
_______ provides building blocks for actively growing regions.
Translocation
Carbohydrate- and nutrient- rich fluid is called _____.
Sap
______, _______, and _____ are transported up and down phloem (bi directional transport).
Sucrose, Hormones, and mRNA
________ describes movement of carbohydrates in phloem.
Pressure-flow theory
______ flow from a source and are released in sink. Sources include ____________. Sinks include _____________.
Dissolved carbohydrates; photosynthetic tissues;growing root and stem tips as well as developing fruits