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LO Chapter 37: Water and Sugar Transport in Plants
Section 37.1-37.4 &…
LO Chapter 37: Water and Sugar Transport in Plants
Section 37.1-37.4 & 37.6
February 14th, 2019
- Describe the evolutionary adaptations that have allowed plants to obtain water and nutrients on land. :
- Roots
- Mycorrhiztyes
- Waxy Cuticle
- Stomata: gas exchange or CO2 and O2.
- Thick Cell Walls
- Pollen, Seed, Flowers, and Fruit: Reproduction and Dispersal
- Vascular System: more water minerals.
- Harden Spores: to protect and disperse zygotes.
- Draw a picture that demonstrates the apoplast, symplast,and transmembrane routes that water and nutrients use to reach the root vascular tissue.
Transmembrane Route
- Goes through everything. If it needs to.
Symplast Route
- Uses cytoplasm and plasmadesmata.
- This allows direct cytoplasm-to-cytoplasm flow of water and other nutrients along concentration gradients.
- The symplast of a plant is the inner side of the plasma membrane in which water and low-molecular-weight solutes can freely diffuse. Symplast cells have more than one nucleus.
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- Draw the pathway of water movement from soil, through plants, to the atmosphere, describing the physical forces along the pathway of water moving upward through the xylem, from the roots to the leaves, explaining how and why water moves.
Water Potential
Water potential has two components:
(1) physical forces, such as gravity or pressure on a plant cell wall;
(2) the concentration of solute in each solution.
Water will always move, via osmosis, in the direction of lower water potential.
Plasmolysis: The shrinking of a plant cell in a hyper-tonic solution such that it pulls away from the cell wall.
The total water potential (Ψw) of a plant cell is the sum of its pressure potential (Ψp) and solute potential (Ψs); it represents the total potential energy of the water in the cell:
Calculation
Ψw = Ψp + Ψs
Pressure Potential: The turgor pressure, resulting from pressure against the cell wall
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- Describe how stomata are opened and closed, and the environmental conditions that trigger these events.
- influx of water to open
- temperature: moist cool.
Open via Guard cells attracted by potassium, Turgor pressure.
photosysyem II, electron transport chain, photo system I
Open Stomata:
- Guard Cells are Turgor
- Moist, Calm, Stable Environment.
Closed Stomata:
- Guard Cells are Flaccid.
- Windy, High Heat, Dry
- Define translocation, describing the substances that are translocated, where in the plant they are translocated to, and why the plant translocates them.
- Translocation: the transport of the products of photosynthesis. (Glucose and Oxygen) Carried out by the phloem..
- The substances that are translocated:
Phloem sap.
- The phloem sap are translocated from the sugar source to sugar sink.
- Sinks usually receive sugar from the nearest sugar sources.
- For each sieve tube, the direction of transport depends on the locations of sugars source of sugar sink that are connected by the tube.
- Draw a figure of the cells involved in translocation, labeling how substances are moved into and through the phloem.
- move sugars from source to sink
- specialized parecama. Cell
- passive flow, sap
Ground Tissues
Parenchyma cells are living and they have a thin cell wall. Because they’re living, if stimulated, they can undergo cell division. They’re function is for food storage, regulation of ions, waste products, and water regulation.
Collenchyma cells have irregular thickness of their cell walls and they are living cells. Their function is to provide extra structural support for the plant. Especially in regions of new growth.
Sclerenchyma cells consist of two types: Fibers and sclereids. When these cells reach maturity, they become dead; however, they do have a function in providing strength and support to the plant. They have thick cell walls that are made from cellulose and lignin.
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Dermal tissue
- forms a protective interface with the environment.
- primarily in the epidermis.
- Guard cells in the epidermis control water loss through stomata.
- trichomes protect the plant from both herbivory and water loss.
- Root hairs are epidermal cell structures that help increase the absorptive area of roots.
- Compare and contrast xylem and phloem transport, in terms of the paths taken, the substances transported, the plant cells and tissues involved, and the forces acting along the way.
Vascular Tissues
Phloem Transport
- It involves the transport of sugars.
- The direction can be either up or down. Depending on where the sink and source are.
- The mechanism that drives this is translocation by positive pressure.
- The tissues involved: sieve tubes elements and the companion cells.
Xylem Transport
- It involves the transportation of water and minerals.
- The directions is almost always upward.
- The mechanism that drives this is transcription by water potential. Water moves up to places that have high water potential to places with low water potential.
Adhesion of and cohesion also helps.
- Tissue involvd: the xylem. the casperian strip. The stomata play a role also.
- Mesophyll cells play a role in both of these transport. Water is involved.
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(a) Dandelions such as this one employ a taproot system—a large central root and a number of smaller lateral roots.
(b) The French marigold employs a fibrous root system—a collection of roots that are all about the same size.
- Sugar/Sucrose made in the Mesophyll cells can travels through the symplast to the sieve tubes. Or the sugar/sucrose exit the symplast and travel through the apoplast into the sieve tubes via Active Transport.
- Sucrose gets into the cell by couple transport with H+. The proton pump in these cells transport H+ up their concentration graident w/ the help of ATP. After that the H+ wants to get back back in so they do that with the couple transport with the sucrose.
- Sugar intake causes the water potential to be lower in the sieve tubes. So osmosis pushes the water into the sieve tubes.
- The water creates a pressure (positive pressue) that causes the sugar to flow withen the Pholem/Sieve tubes.
- The pressure relieved by the sink cell, since the cell is taking the sugar and some water.
- The xylem recycles the water that are used by the pholem.
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Apoplast Route
- Avoids membrane transport.
- can only take water a certain way; near the xylem, the Casparian strip forms an impenetrable barrier to water in the cell walls, and water must move into the cytoplasm to continue.
