Chapter 39: Transportation of Flowering Plants
What does the root system absorb?
Water and minerals
What does a shoot system take up?
CO2 from the atmosphere
What do photosynthetic cells produce?
What are the two main long-distance transport with conducting tissues?
Xylem and Phloem
What are xylem?
Transports water and dissolved minerals
What is phloem?
Transports organic substances in a water sap
What is simple diffusion?
Movement of molecules through a phospholipid bilayer down a concentrated
What is facilitated diffusion?
Transport of molecules across plasma membranes down a concentration gradient with the aid of movement transport proteins
What are two types of membrane transport proteins?
Channels and Transporters
What are channels?
Membrane pores formed by proteins
What are transporters?
Bind to molecules on one side of the membrane in response to differences in solute concentrations
What is osmosis?
Diffusion of water across a selectively permeable membrane in response to differences in solute concentrations
Which way does osmosis ALWAYS occur?
From high to low concentrations
What are aquaporins?
Protein channels that allow facilitated diffusion of water
What is active transport?
Membrane transporter proteins use energy to move substances against their concentration gradients
What is a H+-ATPase proton pump?
Use of ATP to pump protons against a gradient
What is a symporter?
A protein that transports two substances in the same direction across a membrane
When is energy released in the H+-ATPase proton pump?
when protons pass down their gradient used to power active transport
What is a symporter used in?
The uptake of sugars, amino. acids, and nucleotide bases
Where are active transport cells abundant?
In root cell membranes
What does the water content of plants depend on?
What 2 things does osmosis depend on?
1. Solute. concentration
2. Turgor pressure
What is turgor pressure?
Hydrostatic pressure that increases as water enters plant cells
Why does turgor pressure increase?
Because cell walls restrict how much cells can swell
What are the two concepts to understand water potential?
1. To understand the movement of. water in and out of cells
2. To understand the movement of water between entire plants and their environment
What is the equation for. calculating cellular water potential?
What is the solute potential (Ys)
Presence of solutes:
- Pure water = 0
- What with solutes has a negative solute potential
What is the pressure potential (Yp)?
- Turgid cells = positive Yw
- Flaccid and plasmolyze cells have a pressure potential of zero
What are the three forms of tissue-level transport?
1. Transmembrane transport
2. Symplastic transport
3. Apoplastic transport
What is transmembrane transport?
Export of material via membrane proteins, followed by import of the same substance by an adjacent cell
What is an example of transmembrane transport?
Auxin transport aided by carrier proteins
What is symplastic transport?
Movement from cytosol. of one cell to cytosol of another through plasmodesmat
What does symplastic transport allow transport of?
proteins, nucleic acids, and smaller molecules
What is apoplastic transport?
Movement along cell walls and intercellular spaces
What is an example of apoplastic movement?
Water and dissolved materials
In symplastic and apoplastic transport, where do nutrients enter through?
Outer tissues of roots
What substances does apoplastic transport move?
Soil water and dissolved minerals through root epidermal and cortex tissues
Where does apoplastic transport stop?
At root epidermis (barrier to central core of vascular tissue
What prevents apoplastic transport into root vascular tissues?
What kind of flow is used for long-distance transport?
Bulk or mass flow
What is bulk or mass flow?
Mass movement of liquid caused by pressure, gravity, or both
What happens when water is abundant?
What pressure is higher in root xylem and shoot xylem
Where does pressure build up as organic solutes are produced by photosynthesis?
In phloem sap of leaves
Can the transport functions of xylem and phloem be reversed at times?
What are tracheary elements?
Tracheids and vessel elements
What are tracheary elements specialized in?
Water-conducting cells and are dead and empty of cytosol when mature
What element are treachery elements abundant in?
Which treachery element (vessel element or tracheids) have a larger diameter and greater capacity for bulk flow?
What is transpiration?
Evaporation of water from plant surfaces
What allows for pulling water up by bulk flow?
What is the primary form of long distance water transport in plants?
Is there energy needed for bulk flow?
What (indirect) form of energy powers transpiration?
Light Energy from the Sun
What is a characteristic of water is important for transpiration?
What is the cohesion-tension theory?
Cohesion and tension exerted on water by evaporation at plant's surface pulls a continuous stream of water from the soil
What does surface tension increase?
The intercellular spaces of cells, pulling on the water stream in xylem
What do plants produce to prevent water loss?
A waxy cuticle
What plant structure facilitates gas exchange?
When stomata are open...?
O2 and water vapor are released and CO2 is taken up
What are guard. cells?
Cells that close to conserve water
What kind of light stimulates guard cell ion uptake, water flows in, cell expands and stomata opens?
In the stomata, what happens at night?
Ions are pumped out, and the cell deflates
What substance can also close the stomata during the day?
For what plants is leaf abscission a valuable adaptation?
For desert plants and angiosperm trees of seasonally cold habitats
What is the purpose of leaf abscission?
Allows the plants avoid very low leaf water potentials and the consequent danger of xylem embolism
What kind of leaves are efficient for light capture but vulnerable to cold stress?
Broad and thin leaves
What kind of leaves reduces leaf surface evaporation?
Needle or scale-shaped leaves
What does ethylene stimulate from?
What happens after. water supply is cut off to leaf and chlorophyll breaks down?
Revealing carotenoid and xanthophyll pigments (fall colors)
What do enzymes do?
breaks down cell-wall components of separation layer, causing petiole to break off
What is primary phloem?
Occurs in the. vascular. bundles of herbaceous plants
What is secondary phloem?
Occurs as the inner bark. of woody plants
What kind of phloem tissues remain live and retain at. lease some cytoplasmic components?
What are sieve-tube elements?
Arranged at the end to end, together with companion cells from a system to transport. soluble organic substances
Where does phloem sap pass through?
Sieve plate pores
What does a companion cell supply?
mRNA and proteins to sieve tube elements via plasmodesmata because lost its nucleus
How do the sieve-tube elements reduce obstruction to bulk flow?
By losing its nucleus and reduction of most of the cytoplasm
Which structure plays a role in conveying sugars to sieve-tube elements for long-distance transport?
What is used for most long distance transport?
What are the 2 types of phloem loading?
What is symplastic?
Transportation of sucrose form sugar-producing cells of the leaf mesophyll to companion cells and then to sieve-tube elements via plasmodesmata
Does symplastic require energy?
No ATP, because sugar does not cross plasma membranes
Where does symplastic mostly occur, what plants?
Most woody plants
What is partly apoplastic and partly. transmembrane transport?
Loading of. sugar into sieve-tube elements or companion cells from intercellular spaces
Is ATP used for partly apoplastic and partly. transmembrane transport?
Yes, because sugar is moved across the plasma membrane
What kind of plants does partly apoplastic and partly. transmembrane transport occur in?
What is the sugar source?
What is the sugar. sink?
Roots, developing leaves, seeds, fruits
What is phloem transport driven by?
Differences in turgor pressure between cells of a sugar source and sugar sink
Which way can. directions go?
Horizontal or vertical