Biology 173
Study questions week #4
Winter 2016
McNeely
1. Define meristem tissue of a plant. In a plant that has only primary growth (for example a shortlived herbaceous plant such as Arabidopsis), where are the meristems located? Draw a plant with
only primary growth, including both root and shoot systems, and indicate the location of the
meristems.
2. Will the distances between two specific branches on a tree change over the years? Why or why
not?
3. Where are the meristems found on a plant that has experienced primary and secondary growth?
You should be able to name and locate the function of at least 5 different types of meristems. What
is the function of each?
4. Draw a X-section of each of the following:
Stem formed by primary growth only
Root formed by primary growth only
Stem that has experienced a long period of secondary growth
Label the important tissue types in each.
5. What are three functions of the root cap:
6. What would happen to a young tree if I covered its lenticels with vasoline? Which tissues and cell
types would be affected?
7. If I went back to my childhood home, would the height of a tire swing attached to an oak branch
have changed? Will its distance from the tree trunk have changed?
8. Where is the primary phloem of a 3,000 year old bristlecone pine? Where is the primary xylem?
9. Define a circadian rhythm and provide an example of a plant state regulated by a circadian
rhythm.
10. Define induced plant defenses and provide an example.
11. Define a hormone in your own words. What do hormones communicate? What conditions
modify their effects on recipient cells? Explain how auxin fits this definition. What does it
communicate? How are responses different in different plant tissues?
12. How does the function of auxin differ between phototropism and gravitropism?
13. Based on the function of auxin in phototropism and gravitropism, can you come up with a
hypothesis for how auxin might function in hydrotropism? Describe an experiment you could
perform to test this hypothesis.
14. Contrast the effects of auxins and cytokinins on plant growth. How does auxin produce apical
dominance during normal plant growth?
Biology 173
Study questions week #4
Winter 2016
McNeely
15. Explain the role of each of these hormones in plant reproduction:
Auxin
Ethylene
Abscisic acid
Gibberelin
16. Maple leaves infected with a certain fungus often retain green spots around the fungal growth
after the leaf has otherwise, senesced, turned yellow, and fallen from the tree. Suggest a hypothesis
for how the fungus might manipulate plant hormones to achieve this.
17. Witches’ broom, a pattern of localized uncontrolled branching occurs with some fungal
infections of trees. How could alterations of plant hormones cause this effect?
18. Why does auxin travel down but not up plant stems? How does this affect its role in apical
dominance?
19. For the following plant structures, which are formed by secondary growth only, and which are
formed by primary growth: epidermis, cork, cork cambium, xylem, phloem, cortex, leaf, axial bud,
endodermis.
20. Some plants that often experience heavy grazing be deer or other mammals have higher fitness
when grazed than when grazers have been excluded. How could mammalian grazing change the
growth pattern of plants to improve their reproductive success? What hormones might be involved?
21. How do each of the following contribute to efficient photosynthesis by plants?
Root nodules harboring nitrogen fixing bacteria
Mycorrhizae
Circadian rhythms
Phototropism
Apical dominance
Auxin
Cytokinin
Abscissic acid
22. Explain the function of the plant hormone auxin in phototropism of grass seedlings. How does
it stimulate cell walls to lengthen? Describe 2 experiments that showed a chemical substance is
required for this plant growth response.
23. Draw a X-section of a plant stem that has experienced a long period of secondary growth (tree
trunk). Indicate the location where each of the following functions occurs and name the
tissue/structure responsible for this function: support for tree against gravity, water transport, new
growth of vascular tissue, sugar transport, protection from drying out, gas exchange.
24. Christmas cactus is the common name for the lovely plant houseplant pictured below, because it
normally flowers in December (although it is not a cactus). Is this plant likely to be a short-day plant
or a long-day plant?
Biology 173
Study questions week #4
Winter 2016
McNeely
24a. If kept this plant in my college bedroom, where I tended to study and goof off with the light on
until well past midnight, would the plant flower normally during winter? Why or why not?
24b. If I were raising these plants in a greenhouse and wanted them to be blooming in December to
encourage people to buy them as holiday gifts, but I needed to do some work in the greenhouse in
the middle of the night, how might I avoid disrupting their flowering? You should be able to
suggest at least two different strategies (i.e. one involves specific wavelengths of light).
24c. The Christmas cactus has a close relative, the Easter cactus, which blooms in early spring. How
would the responses of this plant to day/night length be similar and different to those of the
Christmas cactus?
24d. Under which of the following conditions (created in a growth chamber) would you expect the
Christmas cactus to bloom?
Day 18 hours, night 6 hours
Day 18 hours, night 18 hours
Day 6 hours, night 18 hours
Day 6 hours, night 6 hours
24e. Under which of these conditions would you expect the Easter cactus to bloom?
Day 18 hours, night 6 hours
Day 18 hours, night 18 hours
Day 6 hours, night 18 hours
Day 6 hours, night 6 hours
25. What is the name of the plant photoreceptor sensitive to red and far red light? Draw or describe
the two forms of this photoreceptor. Which form is directly synthesized by the plant? Which form
breaks down/converts to the other form in the dark? Which form is sensitive to red light and which
form to far red light?
26. Describe 3 different functions of the red/far red photoreceptor. Explain how the structure of
the photoreceptor facilitates these functions.
Biology 173
Study questions week #4
Winter 2016
McNeely
27. Which two known plant photoreceptors respond to blue light? Describe one function of each of
them. In class we discussed a possible third blue photoreceptor. What is its name and what
function may it control?
28. How do each of the following contribute to efficient photosynthesis by plants?
Circadian rhythms
Phototropism
Phototropin
Cryptochrome
Phytochrome