Principles of Biology - Biology 102
Spring Quarter
Lake Tahoe Community College
Instructor: Sue Kloss
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Ch. 36 - Plant Nutrition and Transport
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Intro – some plants are heavy metal accumulators – e.g brake fern – 200x higher than soil, and thrives in these
conditions.
A. brake fern takes up arsenic.
1. Sunflowers and Italian mustard
2. phytoremediation
3. Radioactive metals
B. Transport in plants
1. cells
2. tissues and organs
3. xylem and phloem at
I. Physical forces and transport in plants
A. Review
1. passive transport
2. active transport
3. transport protein
B. Proton Pumps
1. most active transport protein in plant cells
a. uses energy from ATP
b. also contributes to membrane potential
c. proton pumping makes inside of cell negative
2. plants use energy stored in H+ gradient
a. membrane potential
b. cotransport
3. Effects of differences in water potential
a. osmosis
b. water potential
c. Water potential -  = p +s
4. Solutes and pressure always affect water potential
a. pressure potential
b. solute or osmotic potential
5. Quantitative analysis of water potential
a. general model
b. water relations in plant cell model
6. dynamic equilibrium
a. turgor pressure
b. wilted condition
7. transport/movement btn cells- symplast and apoplast
8. bulk flow
II. Uptake and transport of nutrients
A. Plants acquire nutrients from soil and
1. leaves take in CO2
2. Plants get water, minerals and O2 from the soil.
3. Sugars made by plant- composed of CHO
4. Cell respiration breaks down some sugar to provide energy for plant, consuming O2.
5. Plants are net producers of O2
6. Plants take up minerals
B. Plasma membrane of roots control solute uptake
1. root hairs are extensions of epidermal cells
2. solutes and nutrients (ions) enter the epidermis
3. must pass through plasma membrane of root
C. Transpiration pulls water up xylem vessels
1. works against gravity
2. supplies nutrients to stem and leaves
3. two types of cells in xylem
a. tracheids
b. vessels
4. xylem sap is pulled - tension - cohesion mechanism
a. transpiration
b. cohesion
c. adhesion
d. steep diffusion gradient
e. cohesion resists this
f. called transpiration-cohesion-tension mechanism
5. guard cells control transpiration
a. transpiration works for and against plant
b. plant can lose a lot of
c. as long as water is present, no problem
d. stomates help control water balance
e. guard cells keep stomata open
f. How do guard cells work?
6. Phloem transports sugars, food molecules of the plant made by Ps.
a. food conducting cells are sieve tube members
b. phloem sap
c. sugar source
1) Ps
2) stored starch
d. sugar sink- sugar is stored or consumed - growing parts, fruits, and non Ps parts
e. storage structures (taproot of beet) may alternately be sources or sinks
f. how does sugar move? pressure flow mechanism
1) sugar moves by active transport into phloem cell
2) conc. gradient - water diffuses in.
3) sugars sink, pushed by water, followed by water (osmosis)
4) sugar moves at same rate as water
5) how do researchers study? aphids
Ch 36 objectives
1. Describe how proton pumps function in transport of materials across plant membranes, using the terms proton
gradient, membrane potential, cotransport, and chemiosmosis.
2. Define osmosis and water potential. Explain how water potential is measured.
3. Explain how solutes and pressure affect water potential.
4. Explain how the physical properties of plant cells are changed when the plant is placed into solutions that have
higher, lower, or the same solute concentration.
5. Define the terms flaccid, plasmolyze, turgor pressure, and turgid.
6. Explain how aquaporins affect the rate of water transport across membranes.
7. Distinguish between the symplast and the apoplast.
8. Describe three routes available for lateral transport in plants.
9. Define bulk flow and describe the forces that generate pressure in the vascular tissue of plants.
10. Relate the structure of sieve-tube cells, vessel cells, and tracheids to their functions in bulk flow
11. Explain how mycorrhizae enhance uptake of materials by roots.
12. Explain how the endodermis functions as a selective barrier between the root cortex and vascular cylinder
13. Describe the potential and limits of root pressure to move xylem sap.
14. Define the terms transpiration and guttation.
15. Explain how transpirational pull moves xylem sap up from the root tips to the leaves.
16. Explain this statement: “The ascent of xylem sap is ultimately solar powered.”
17. Describe the role of guard cells in photosynthesis-transpiration.
18. Explain how and when stomata open and close. Describe the cues that trigger stomatal opening at dawn.
19. Explain how xerophytes reduce transpiration.
20. Define pressure flow. Explain the significance of this process in angiosperms.