Name: 
 

Chapter 39



Multiple Choice
Identify the letter of the choice that best completes the statement or answers the question.
 

 1. 

All of the following may function in signal transduction in plants except
a.
calcium ions.
b.
nonrandom mutations.
c.
receptor proteins.
d.
phytochrome.
e.
second messengers.
 

 2. 

Charles and Francis Darwin concluded from their experiments on phototropism by grass seedlings that the part of the seedling that detects the direction of light is the
a.
tip of the coleoptile.
b.
part of the coleoptile that bends during the response.
c.
root tip.
d.
cotyledon.
e.
phytochrome.
 

 3. 

Vines in tropical rain forests must grow toward large trees before being able to grow toward the sun. To reach a large tree, the most useful kind of growth movement for a tropical vine presumably would be the opposite of
a.
positive thigmotropism.
b.
positive phototropism.
c.
positive gravitropism.
d.
sleep movements.
e.
circadian rhythms.
 

 4. 

Plant hormones can have different effects at different concentrations. This explains how
a.
some plants are long-day plants and others are short-day plants.
b.
signal transduction pathways in plants are different from those in animals.
c.
plant genes recognize pathogen genes.
d.
auxin can stimulate cell elongation in apical meristems, yet will inhibit the growth of axillary buds.
e.
they really don't fit the definition of "hormone."
 

 5. 

We tend to think of plants as immobile when, in fact, they can move in many ways. All of the following are movements plants can accomplish except
a.
growth movements up or down in response to gravity.
b.
folding and unfolding of leaves using muscle-like tissues.
c.
growth movements toward or away from light.
d.
changes in plant growth form in response to wind or touch.
e.
rapid responses using action potentials similar to those found in the nervous tissue of animals.
 

 6. 

Both red and blue light are involved in
a.
stem elongation.
b.
photoperiodism.
c.
positive phototropism.
d.
tracking seasons.
e.
all of the above
 

 7. 

Plants often use changes in day length (photoperiod) to trigger events such as dormancy and flowering. It is logical that plants have evolved this mechanism because photoperiod changes
a.
are more predictable than air temperature changes.
b.
alter the amount of energy available to the plant.
c.
are modified by soil temperature changes.
d.
can reset the biological clock.
e.
are correlated with moisture availability.
 

 8. 

A long-day plant will flower if
a.
the duration of continuous light exceeds a critical length.
b.
the duration of continuous light is less than a critical length.
c.
the duration of continuous darkness exceeds a critical length.
d.
the duration of continuous darkness is less than a critical length.
e.
it is kept in continuous far-red light.
 

 9. 

Florigen is a flowering signal, not yet chemically identified, found in
a.
flowers.
b.
leaves.
c.
roots.
d.
seeds.
e.
floral buds.
 

 10. 

In extremely cold regions, woody species may survive freezing temperatures by
a.
emptying water from the vacuoles to prevent freezing.
b.
decreasing the numbers of phospholipids in cell membranes.
c.
decreasing the fluidity of all cellular membranes.
d.
producing canavanine as a natural antifreeze.
e.
increasing cytoplasmic levels of specific solute concentrations, such as sugars.
 

 11. 

The initial response of the root cells of a tomato plant watered with seawater would be to
a.
rapidly produce organic solutes in the cytoplasm.
b.
rapidly expand until the cells burst.
c.
begin to plasmolyze as water is lost.
d.
actively transport water from the cytoplasm into the vacuole.
e.
actively absorb salts from the seawater.
 



 
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