回顧問題不定期更新 Study Questions are Made by Prof. Cruz & Prof. Moore from Oberlin College & Conservatory?

Lectures 21 & 22: Plant Hormones & Responses?

1. Why are second messengers important for signal transduction in cases where hormones have membrane-bound receptors?

2. How do plant stems bend toward the light? In other words, what happens to the cells in the stem that allow the stem to exhibit positive phototropism? How does auxin affect this process?

3. Auxin can move up or down within roots. What does this tell you about the location of PIN proteins in root cells?

4. Geranium plants exhibit strong apical dominance under normal conditions, yet most people like to have geraniums that are highly branched. How could a gardener create a “bushy” geranium if given a new geranium seedling? How does this relate to plant hormones?

5. Imagine that we have discovered dwarf corn plants that we believe are deficient in gibberellin. In order to test this, we apply synthetic gibberellin to the SAM region of the dwarf corn seedlings. As controls, we apply gibberellin to normal corn seedlings as well, but we also grow normal and dwarf plants with no additional gibberellin applied. After application of gibberellin, we note that the normal seedlings have grown even taller than the normal seedlings in which no gibberellin was applied. However, we unexpectedly discover that the application of gibberellin causes no effect on stem elongation in the dwarf seedlings vs. the dwarf seedlings in which no gibberellin was applied. How can you explain these results? (It might be helpful for you to draw these results before you answer the question.)

6. Why does “one bad apple spoil the bunch?”

7. What hormone might not be performing its normal function if a plant never developed winter buds? Describe two hypotheses related to hormone function that would account for this abnormality in the buds.

8. Why can the ethylene triple response be beneficial to seedlings in the soil?

9. Imagine that we discover the following plant “oddities”. Which hormone(s) do you think might be involved in each situation?

a) an Arabidopsis plant that produces malformed xylem and phloem

b) an oak tree is abnormally short and shrubby

c) an apple tree whose fruits never ripen.

10. Why is it important for a layer of cork cells (i.e., cells that have cell walls with suberin in them) to be laid down in an abscission zone?

11. What would happen to a plant if you applied a chemical that blocked ABA receptors (in other words, prevented ABA binding) in the leaf? When you answer the question, think more broadly than just the immediate response to blocked ABA receptors—i.e., what would the long-term effect of blocked ABA receptors be?

12. What environmental stimulus causes loss of leaves in drought deciduous trees?

13. What kind of tropic response (phototropism, thigmotropism, etc.) is typically exhibited in each of the following situations? (There is one “best” answer for each example). Be sure to indicate whether the tropism is positive or negative.

a) a vine on a tree

b) a geranium plant on a windowsill

c) normal roots

d) a parasitic dodder seedling in search of a host plant

e) a bend in a stem caused when a potted plant is turned sideways

14. What are the differences among phototropism, solar tracking, and photonasty.

注意本文集的Study Question都是不定期更新且沒有答案喔~?

離久-張所長