Unit 3 Review Questions

Question 1

In what kinds of habitats are most carnivorous plants found? Why are they found in those habitats and not in others?

Question 2

What is the definition of holoparasite and hemiparasite? Give examples of each.

Question 3

Is the level of carnivory in a plant dynamic? When might the costs of carnivory exceed its benefits? Can discuss using sundew example.

Answer 3

Level of s tickiness» is a dynamic relationship.

Question 4

How do epiphytes acquire materials?

Question 5

What is a good way to assess how damaging parasitic plants are to their hosts? Think of an experiment you may run to do this (hint: grow a group of plants w/ a parasite and one without). Think about sufficient sample size, and what you might measure to assess whether or not a parasitic plant is damaging. Could you use this to asses differences in damages due to hemiparasite vs holoparasite?

Question 6

What exactly is the phytochrome? What are the functions of this molecule? What are the two forms? What is required to switch between one form and another?

Question 7

Name at least three places in plant tissues where phytochrome will be found.

Question 8

What are three specific functions or responses would be missing in a plant that lacked phytochrome?

Question 9

Which form of phytochrome is considered to be the inactive form and which form is considered to be the active form? Why?

Question 10

How does specifically red light and Pfr trigger germination?

Question 11

Under what conditions would you expect to see higher Pfr/Pr ratios- seeds exposed to far red or red light; seedlings growing in open environments or shade; leaves in lower part of the canopy or top part of the canopy? Be able to explain why.

Question 12

What is the definition of photoperiodism? How specifically do plants use phytochrome to determine photoperiodism?

Question 13

In photoperiodic responses, do plants measure the length of the day or night? What experiment did we discuss in class that provided this answer?

Question 14

What is the difference in the day/night length requirements between a long day plant and a short day plant? Be able to describe what this translates into in terms of forms of the phytochrome (and specifically ratios of Pfr/Pr).

Question 15

What would the consequences in terms of ability to flower, of transplanting a long night plant to the tropics (where day length = night length year round (12 hours daylight everyday)? Explain your answer.

Answer 15

Wouldn’t be able to flower. Shorter night= less pfr to pr . Long night= more pfr to pr

Question 16

What are the definitions of phototropism, thigmotropism and gravitropism and give an
example of each.

Question 17

What color of light is required to stimulate phototropism? What is the specific receptor for
this light? How do we know that the signal to detect blue light occurs in the tip of grass
seedlings?

Question 18

What is the Cholodny-Went hypothesis, and how does it explain how an asymmetric
distribution of auxin develops in stems in response to unidirectional light. Describe the
experiment we discussed in class that supported this hypothesis.

Question 19

What is the Acid Growth Hypothesis? What role does auxin play in explaining the Acid
Growth Hypothesis? Why is this hypothesis important to understand with respect to
phototropism?

Answer 19

Allows hydrogen ions to go into the cell. Allows cross bridges to loosen and cells can enlarge (in shoots).

Question 20

What does polar transport of auxin refer to? What role do AUX1 and PIN protein carriers
play in regulating both vertical and lateral polar transport of auxin?

Question 21

What is the definition of apical dominance?

Question 22

When you pinch off the tip of a house plant to make it more bushy, how have you
manipulated hormone levels, which hormone specifically, what growth response will result
and why?

Question 23

What specific organelle in both the shoot and root is responsible for the perception of
gravity? Where is it located in roots? How do these organelles function in this capacity? If
these organelles are missing, does that mean the plant is unable to sense gravity?

Question 24

Auxin increase has a differential effect on cell elongation in stems and roots. Be able to
explain what the difference is and how it explains observed responses in phototropism and
gravitropism.

Question 25

Briefly explain 2 other roles auxin plays in plants other than apical dominance, phototropism
and gravitropism.

Question 26

Are root and shoots positively geotropic, negatively geotropic or neither?

Question 27

What important roles we discussed in class that the hormones ethylene, gibberellins,
cytokinins and abscisic acid play in plants?

Question 28

Describe the sequence of steps in the hypersensitive response.

Question 29

What are R genes and how do they work? What is required for them to trigger a
hypersensitive response (HR)?

Question 30

What is systemic acquired resistance (SAR) and how is it related to the hypersensitive
response?

Question 31

Describe the role of systemin in plants

Question 32

What are induced and constitutive defenses? What is the risk of relying on only one vs.
the other? In what situations would it be beneficial for plants to use one or the other?

Question 33

Describe the recruitment of parasitoid wasps by plants and its role in plant defense. Why
is this called indirect defense? Why is this described as a tritrophic interaction?

Question 34

What are mechanical defenses? Give 3 examples.

Question 35

What are chemical defenses? Give 3 examples of how they defend (what affect they
have on herbivores), and 3 examples of chemically distinct groups

Question 36

Give an example of biotic defense strategy used by plants.

Question 37

Why are chemical defenses often called secondary compounds?

Question 38

Why should investment in defenses be considered in cost/benefit type framework?

Question 39

How does the cuticle act as a defense?