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Active Lecture Questions for
BIOLOGY, Eighth Edition
Neil Campbell & Jane Reece
Chapter 39
Plant Responses to Internal and
External Signals
Questions prepared by
Jung Choi,
Georgia Institute of Technology
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings.
Plant versus Animal Signal Responses
In what ways do plant signaling and response
pathways differ from animal pathways?
a) Plant hormones do not circulate; animal hormones
do.
b) Plants do not respond to touch; animals do.
c) Animal cells have many more protein kinases than
plant cells.
d) all of the above
e) none of the above
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings.
Plant Hormones
Spraying plants daily with compound X causes
dwarfism, compared with untreated control plants.
Is this evidence sufficient to conclude that
compound X is a plant hormone?
a) yes
b) No, a receptor for compound X must be identified.
c) No, compound X must work at nanomolar
concentrations.
d) No, a second messenger must be identified that
transduces the compound X signal.
e) No, plants must synthesize compound X at
physiologically active concentrations.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings.
Plant Hormone Genetics
To study the signal transduction pathway for
hormone Y, one should look for mutant plants that
do which of the following?
a) fail to respond when hormone Y is applied
b) show a constitutive response even in the absence of
hormone Y
c) are rescued by application of hormone Y
d) either a or b
e) any of the above
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings.
Phytochrome
Tomato plants grown in shade show increased
susceptibility to herbivory by insects compared to
plants grown in light. If this effect is mediated by
phytochrome, then which of the following is/are
true?
a) It will be reversed by far-red light.
b) It will be reversed by red light.
c) Phytochrome-deficient mutants will be less sensitive
to herbivores.
d) Both a and c are true.
e) Both b and c are true.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings.
Stress Signaling
An Arabidopsis mutant deficient in the G-proteincoupled receptor protein gene GCR1 exhibits
hypersensitivity to abscisic acid in assays of gene
expression and stomatal closure (S. Pandey & S. M.
Assmann, Plant Cell 16 (2004):1616–1632). These
results indicate that the role of GCR1 in abscisic acid
signaling is which of the following?
a) GCR1 is a receptor for abscisic acid.
b) GCR1 is an inhibitor of abscisic acid signaling.
c) GCR1 stimulates abscisic acid synthesis.
d) Abscisic acid signaling inhibits GCR1.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings.
GCR1
GCR1 mutant plants are more drought resistant than
wild-type plants. What other phenotypes may be
expected of these mutants?
a) cold resistance
b) salt tolerance
c) reduced seed germination
d) all of the above
e) none of the above
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings.
Gene-for-Gene Disease Resistance
Why do bacteria have Avr alleles that are recognized by
plant R genes? In other words, what prevents Avr alleles
that do not interact with R genes from becoming fixed in the
pathogenic bacterial populations?
a) Avr genes cannot mutate without losing their
function in pathogenicity.
b) Plant R loci can mutate faster than bacterial Avr
genes.
c) Plants have numerous R genes, most of which have
multiple variants, so any Avr allele will eventually
encounter a host plant with an effective R gene.
d) Bacteria limit their Avr alleles to those that won’t
completely eliminate their host plants.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings.