BY 124 SI Worksheet 3
1. Phloem moves sugar:
a. Without the use of any energy from the plant- no, the companion cells actively transport
sugars into sieve tube
b. By active transport through the sieve tube cells- no, passively move due to concentration
gradient pushing h2O
c. Against the flow of xylem – not necessarily, sugars also move from roots to the leaves through
the same process
d. By utilizing pressure gradients created by differing solute concentrations
e. 2 or more of the above
C and D are correct, so E
2. Identify the incorrectly paired relationship and type of mutualism:
a. A holly living on an oak tree – epiphytic – holly is parasitic
b. Spanish moss living on a cypress tree – parasitic – Spanish moss is epiphytic
c. Bacteria living in a plant’s vascular system – symbiotic – parasitic! When N fixing bacteria is in
nodule, its symbiotic
d. Phosphate producing fungus in a plant’s rhizome - symbiotic
e. 2 or more of the above
3. A guard cell may close because:
I. A plant has an under-abundance of water in the vacuole -T
II. A plant’s circadian rhythm releases hormones that cause closing –T
III. A plant’s K+ ion concentration is higher inside the cell than outside - ion concentration must
be smaller inside cell so water rushes out of cell to surrounding to solvate it and closes cell
a. I and II
b. Only II
c. I and III
d. II and III
e. I, II, and III
4. Explain how the transpirational pull cohesion adhesion mechanism works
-no energy of plant is used
5. What controls the opening and closing of the guard cells and what stimuli cause this?
Water levels fluctuate with the flow of K+ ions- more ions in the cell- more turgid -> more open
Water availability, light, CO2 levels, and hormones all control this.
6. Discuss how phloem is able to move sugar throughout the plant
-ion channels to actively remove sugars
7. Describe the cycle that nitrogen undergoes in the environment.
Keep in mind that the nitrogen in plants and animals isn’t a single form, but rather part
innumerably many unique and complex molecules. Leghemoglobin is used to keep O away from
bacteria
8. Discuss the process by which nodules are formed on the genetic and the cellular level.
9. Discuss the differences between parasitic, carnivorous, and epiphytic plants.
Epiphyte: grows on another plant, produces & gathers own nutrients
Parasite: absorb water, minerals from host
Haustoria: special roots that can tap into the host
Carnivorous: do photosynthesis but also capture small insects/animals