Download presentation
Presentation is loading. Please wait.
Published byTyler Wilkerson Modified over 9 years ago
1
Also Known As Chapter 36!! Transpiration + Vascularity
2
Transport Overview
3
3 Types of Transport in Vascular Plants 1. Transport of water & solutes by individual cells 2. Short-Distance transport of substances between cells at the tissue level 3. Long-distance transport within the xylem & phloem among the entire plant
4
From B4 Passive Transport – movement down a gradient Does NOT require energy Active Transport – Movement against a electrochemical gradient Requires energy Most solutes must use transport proteins Aquaporin – channel (transport) protein for water
6
Proton Pumps Uses energy from ATP to pump out hydrogen ions from the cell Establishes a proton gradient with higher [H+] outside the cell The electrical difference is called a membrane potential Potential energy is therefore created As the H+ ions diffuse back in, they can do work
7
Name two processes that used proton pumps. What is cotransport? How does it relate in the processes named above?
9
Water Potential ( Ψ ) Water moves from High concentration to Low concentration via osmosis Equivalently, water moves from high water potential to low water potential Water potential is the combined effect of Solute Concentration Physical Pressure Ψ = Ψ s + Ψ p
10
Water Potential (Page 2) Solute potential ( Ψ s) is proportional to the number of dissolved solute particles Also called Osmotic Potential Ψ s of water = 0 Addition of solute Decrease in potential Ψ s ≤ 0
11
Water Potential (Page 3) Pressure Potential ( Ψ p) Physical pressure on a solution Can be (+) or (-) Water is usually under a positive pressure potential Turgor pressure – when cell contents press the plasma membrane against the cell wall Drying out = Negative pressure potential
12
Water Potential Examples
14
Roots & Water Absorption Root hairs = absorption of water Root epidermis cortex vascular cylinder To rest of plant via xylem Mycorrhizae are important for absorption as well
16
Tonoplast (Vacuolar Membrane) Regulates molecular traffic between the cytosol & vacuolar contents Symplast Cytoplasmic continuum consisting of the cytosol of cells and the plasmodesmata connecting the cytosols. Crosses membrane early in the process Apoplast Continuum of cell walls + extracellular spaces Only crosses a membrane at endodermis
17
Casparian Strip In the endodermis Ensures that any water or solutes must pass through a plasma membrane before entering xylem Critical control point Again, plasma membrane controls what can enter the xylem
18
Bulk Flow Water movement from regions of high pressure to regions of low pressure In xylem, water & minerals travel by bulk flow Called xylem sap Xylem travels from Roots Stem (xylem) Leaves (exit thru stomata)
19
1. Root pressure or “push” 2. Transpiration or “pull” What powers the bulk flow?
20
VASCULAR TRANSPORT -- Starts with stomatal opening -- Transpirational Pull
21
Root Pressure or “push” Water diffusing into the root cortex = positive pressure This pressure forces fluid UP the xylem Weak force – can only propel fluids up a couple of feet
22
Transpirational Pull Your book calls this: transpiration-cohesion-tension mechanism In leaves, water is lost through stomata Why? Lower water pressure in air than in leaves Water is drawn up in to this area of negative pressure Water molecules pull up other water molecules Cohesion – water on water action Adhesion – water to cell wall action Via Hydrogen bonds
24
Transpiration/Cohesion 1 molecule of H2O evaporates due to transpiration, another molecule is drawn from the roots to replace it. High humidity = DECREASE transpiration Wind = INCREASE transpiration Increasing light intensity = INCREASE transpiration Close stomata = NO transpiration
25
Stomata 90% of water lost by plants is through stomata Stomata account for 1% of leaf surface area Guard cells control opening & closing of stomata
26
What causes stomatal opening? 1. Depletion of CO 2 within air spaces Photosynthesis consumes CO 2 = stomata open IF placed in chamber w/o CO 2, stomata open 2. Light 3. An increase in K+ ions Lowers water potential of guard cells Water flows into guard cells stomata open
27
What closes stomata? 1. Lack of water – guard cells lose volume & close 2. High Temp. – stimulates cell respiration & CO 2 accumulates inside leaf 3. Abscisic Acid – produced in mesophyll cells in response to dehydration
28
Phloem Translocation Photosynthetic products leave the leaves and travel throughout the plant Mechanism is called pressure flow Sieve tube elements carry sugar from source to sink Source – leaves (net producer of sugar) Sink – roots (net consumer of sugar)
29
Sucrose is added at the sugar source (leaves) Electrochemical gradient is created to move sucrose into phloem by cotransport Decreases water potential in phloem, so creates positive pressure
Similar presentations
© 2024 SlidePlayer.com Inc.
All rights reserved.