C H A P T E R
15
Chapter Expectations
Briefly explain each of the following points.
• Plants have specialized tissue that continue
to grow throughout life. These regions are
collectively called meristem. (15.1)
• There are two types of meristem tissue,
apical and lateral meristem. (15.1)
• The growth and development of all plants
are regulated by hormones. (15.1)
• There are two classes of plant hormones,
promoters and inhibitors. Promoters include
auxins, gibberellins, cytokinins, and
oligosaccharins. Inhibitors include abscisic
acid (ABA) and ethylene. (15.1)
• Commercial growth regulators are hormonelike chemicals used by agriculturists and
horticulturists. (15.1)
• Plants respond to external stimuli by
showing directional growth called tropisms.
The three main tropisms are in response to
light (phototropism), gravity (gravitropism),
and touch (thigmotropism). (15.1)
• Plants also exhibit nastic responses, which
are responses to stimuli in a non-directional
and non-permanent way. Nastic movements
are a result of changes in turgor pressure in
the cells at the base of the leaf. (15.1)
R E V I E W
• Humans influence the growth and
development of plants by using plant
growth regulators, which are synthetic plant
hormones. (15.1)
• Plants are adapted to survive in their
environments and humans are able to take
advantage of these traits for our own use.
(15.2)
• Recent technologies, such as artificial
selection, hybridization, cloning, and gene
transfer technology are used to improve the
yield and quality of crop plants. (15.3)
Language of Biology
Write a sentence using each of the following words or
terms. Use any six terms in a concept map to show
your understanding of how they are related.
•
•
•
•
•
•
•
•
•
•
meristem
apical meristem
lateral meristem
vascular cambium
cork cambium
auxin
gibberellic acid
gibberellins
cytokinins
oligosaccharins
•
•
•
•
•
•
•
•
•
•
abscisic acid (ABA)
ethylene
tropism
phototropism
gravitropism
thigmotropism
nastic movement
tissue culturing
callus
gene transfer
technology
UNDE RSTAN DIN G CON CEPTS
1. Describe an example of a modern plant-based
technology and an example of an ancient plant
based technology.
2. Decide if the following statement is correct and
support your answer. If the statement is
inaccurate, correct it. Plants manufacture
products such as fragrance molecules for use
in perfumes.
3. Potatoes grown today make crisper potato
chips than potatoes grown a century ago. What
technology is probably responsible? Give
reasons for your answer.
4. What is the goal of cross-breeding? What is an
organism produced by cross-breeding
commonly called?
6. A tulip blossom opens wide in the sunshine
but shuts when skies are cloudy or rain begins
to fall. Explain why this action is NOT an
example of a tropism.
7. How do plants control their own growth and
development?
8. Classify each of the following as either a
growth promoter or a growth inhibitor. Explain
your answer.
(a) Hormones that trigger the ripening of fruit
(b) Hormones that cause tropisms
9. Where is the meristem located in a young,
immature plant? In an older, mature plant?
10. Explain why a mature plant can never be
regarded as “fully grown.”
5. Define tropism in plants. Give an example of a
positive tropism and a negative tropism.
Using Plants • MHR
579
11. Choose one modern plant technology and
describe how it imitates nature’s own methods
and how it differs from what happens in nature.
12. Some people think that “artificial selection” is
a modern plant technology. Is it? Support your
answer.
13. Sunflowers are so named because the flower
heads rotate throughout the day to face the Sun.
As the sky darkens at sunset, the heads droop.
Next morning at sunrise, they spring up to face
the light again. Is this an example of positive
phototropism? Give reasons for your answer.
14. Why do orchard keepers spray developing
fruits with auxin? What other hormones might
they use during a growing season? Explain
your answers.
15. A plant is placed on its side in the dark.
Explain the growth of the plant’s stem and
roots in terms of stimuli and the action of
hormones.
IN QU IRY
17. The list below describes different stages of a
naturally ripening pear. The terms are not in
order. Organize the terms into their proper
sequence. At what stage would you expect the
ethylene levels in the plant to be highest and at
what stage would you expect the ethylene
levels to be lowest:
(a) Pale yellow, firm, slight breakdown in cell
structure
(b) Deep yellow, soft, further breakdown in cell
structure
(c) Yellow-green, hard, cell structure intact
(d) Bright green, hard, cell structure intact
(e) Deep yellow, very soft, extensive
breakdown in cell structure
18. Design an experiment to test the effect of
different colours of light on phototropism in
one plant. What would be your control
situation? What variables would you use?
Write out an hypothesis you could test with
your experimental procedure. Describe
hypothetical data that you would collect if
your data supported your hypothesis. Describe
hypothetical data that you would collect if
your data did not support your hypothesis.
19. Explain the difference between nastic
movements and tropic movements. If you
observed movement in a plant, how could you
experimentally test whether it was a tropic or a
nastic movement?
580
MHR • Plants: Anatomy, Growth, and Functions
Number of Flowers Produced by Plants
500
Number of plants
16. You have been invited to listen to a seminar
given by Dr. Shengwu Ma on creating edible
vaccines. Your colleagues do not understand
his research. Write a hypothesis concerning his
research. What are the predictions of Dr. Ma
and his team with regards to the hypothesis?
400
300
200
100
0
4
8
12
16
20
24
28
Number of flowers per plant
20. A horticultural researcher who is attempting to
develop drought-tolerant garden plants has
identified a population of wild daisies of an
unusual and desirable colour. The graph shown
above illustrates the number of flowers
produced per plant by this population.
(a) How many total plants are there in this
population?
(b) Suppose the researcher hopes to reproduce
the daisies by asexual methods, such as
digging up and dividing root clumps.
Which plants will probably yield the most
flowers next season? Explain your answer.
(c) Suppose the researcher hopes to reproduce
the daisies by sexual methods, that is, by
planting seeds. Collecting seeds is easier
than digging roots. Should the researcher
collect seeds from all of the plants, or just
from the plants you identified in (b)?
Explain your answer.
Increase in height after
10 days (mm)
21. A researcher has been studying the effects of
gibberellin placed on the roots of bean plants.
The results of placing different concentrations
of gibberellin on the roots are presented in the
graph shown here.
(a) Given these data write a conclusion to the
experiment.
(b) After the experiment is over, what steps
would need to be taken to return the plant
stems back to their original vertical
position. Support your answer.
60
50
40
30
20
10
0
100 200 300 400 500 600 700 800
Concentration of gibberellin (ppm)
COMMU N ICATIN G
22. What are the main goals of plant technologies?
Describe the impact of these technologies on
the biosphere.
23. Give one example of a cereal crop and one
example of a root crop. Which crop always
involves meiotic cell division. Write an
explanation of why the other crop type can be
raised without involving meiotic cell division.
24. What is the goal of gene transfer technology?
Briefly describe the process that must be
carried out. Support your description with
drawings.
25. Experts recommend that those with small yards
plant corn in blocks of at least 12 plants,
spaced about 15 cm apart. If the blocks contain
fewer plants, the ears of corn do not develop
full sets of kernels. What do you think is the
cause of this failure to develop? Would this
knowledge influence how you would sow seed
on a larger farm?
26. Compile a table of the plant products that
people use. Divide your list into the following
categories: (a) forestry, (b) spices, (c) chemicals,
(d) lumber, (e) fuel, (f ) food, (g) medicine, and
(h) horticulture. Give at least two examples for
each category. Draw a chart showing the
categories, the list of the plant or plants, and
the use people make of the plant or plants.
Display this information using at least one
other method such as a graph, a chart, a
diagram, a flowchart, or a concept diagram.
27. Raspberries sold in a plastic-wrapped basket
usually ripen, and then spoil, sooner than fruit
that is not wrapped. Write a short paragraph to
account for this observation.
M A KIN G CON N ECTION S
28. Gene transfer technology is a promising
technology. Possible benefits include creating
and improving resistance to disease-causing
viruses, to insect predators, or to herbicides so
the herbicides can be used to control weeds
without killing crop plants. However, like all
technologies, gene transfer technology could be
used unethically or inappropriately. Give
examples of how gene transfer technology can
be used for potential benefits and how it may
also be used inappropriately. Provide a brief
discussion for each example.
29. What are the ecological consequences of
altering genetic material? For example, what
might happen if altered plant or animal species
without natural predators were introduced into
a new environment?
Using Plants • MHR
581