Plant Physiology

Plant Physiology (Biology 327) - Dr. Stephen G. Saupe; College of St. Benedict/ St. John's University; Biology Department; Collegeville, MN 56321; (320) 363 - 2782; (320) 363 - 3202, fax; ssaupe@csbsju.edu

Quiz: Phloem Transport

Definition Question: Using a single sentence (or two), define or describe the following.

P-protein
non-reducing sugar
translocation
photosynthates
invertase
girdle

Multiple Choice Questions:

1. P-protein:
    a. was once called slime
    b. can occur in various forms including crystalline, granular and fibrous
    c. is dispersed throughout the sieve element
    d. is initially synthesized in the companion cells
    e. just occurs in angiosperms
    f.   plugs sieve pores when the sieve elements are damaged
    g. is comprised of amino acids
    h. all of the above are correct except f & g
    i.   all of the above are correct
    j.   none of the above are correct

2. When damaged, sieve elements are plugged by:
    a. p-protein
    b. callose
    c. slime
    d. beta 1,3-glucans
    e. guttation droplets
    f.   a & b are correct
    g. a, b, and d are correct
    h. a, b, c and d are correct

3. Phloem contents are transported from:
    a. high water potential to low water potential
    b. high pressure to low pressure
    c. an area of low sugar concentration to an area of high sugar concentration
    d. from a sink to a source

4. Which of the following is most likely to be a source?
    a. young leaves
    b. developing fruits
    c. taproots in the spring
    d. taproots in the summer
    e. flowers

5. Which of the following materials would you least likely expect in the phloem of all plants?
    a. asparagine
    b. potassium
    c. sucrose
    d. stachyose

Scratch Question: Put a line through the structures in the following list that are uncommon or not likely to be found in a sieve element.

cytoplasm	golgi body	nucleus
ER	mitochondria	plasma membrane
plastids

Sequence Question: Draw a double osmometer. Label the left side A and the right side B. If the system is initially filled with water and then sucrose is added to side (A), number the following in the appropriate sequence of occurrence. The first one is done for you.

1.	sucrose is added inside the membrane on Side A
	flow stops (no net flow into/out of the membranes or from one side to the other)
	pressure increases on Side A
	pressure increases on Side B
	sucrose is evenly distributed in the system
	water and dissolved sucrose flows from Side A to Side B
	water enters the membrane on Side A
	water exits the membrane of Side B
	water flows from Side B to Side A

Short Answer Questions:

Explain the trapping hypothesis for symplastic transport of sucrose into the sieve tubes elements.
What is the function of companion cells?
There are three major types of companion cells. How are these similar?
Explain how solutes are loaded in the phloem.
Explain why flooding the apoplast surrounding a sieve element with an alkaline buffer inhibits phloem transport.
Compare and contrast how woody plants and herbaceous eudicot plants can be girdled.

Complete the Sentence Question:

Four types of cells found in the phloem are . . .
Three things that we learned about the phloem from studies with aphids are . . .
A source is . . .