Table of contents

1. Introduction to Biology2h 42m
2. Chemistry3h 37m
3. Water1h 26m
4. Biomolecules2h 23m
5. Cell Components2h 26m
6. The Membrane2h 31m
7. Energy and Metabolism2h 0m
8. Respiration2h 40m
9. Photosynthesis2h 49m
10. Cell Signaling59m
11. Cell Division2h 47m
12. Meiosis2h 0m
13. Mendelian Genetics4h 44m
14. DNA Synthesis2h 27m
15. Gene Expression3h 6m
16. Regulation of Expression3h 31m
17. Viruses37m
- Viruses
  37m
18. Biotechnology2h 58m
19. Genomics17m
- Genomes
  17m
20. Development1h 5m
21. Evolution3h 1m
22. Evolution of Populations3h 53m
23. Speciation1h 37m
24. History of Life on Earth2h 6m
25. Phylogeny2h 31m
26. Prokaryotes4h 59m
27. Protists1h 12m
28. Plants1h 22m
29. Fungi36m
- Fungi
  19m
- Fungi Reproduction
  17m
30. Overview of Animals34m
- Overview of Animals
  34m
31. Invertebrates1h 2m
32. Vertebrates50m
33. Plant Anatomy1h 3m
34. Vascular Plant Transport1h 2m
- Water Potential
  1h 2m
35. Soil37m
- Soil and Nutrients
  20m
- Nitrogen Fixation
  16m
36. Plant Reproduction47m
- Flowers
  33m
- Seeds
  14m
37. Plant Sensation and Response1h 9m
38. Animal Form and Function1h 19m
39. Digestive System1h 10m
- Digestion
  1h 3m
- Blood Sugar Homeostasis
  7m
40. Circulatory System1h 49m
41. Immune System1h 12m
42. Osmoregulation and Excretion50m
- Osmoregulation and Excretion
  50m
43. Endocrine System1h 4m
- Endocrine System
  1h 4m
44. Animal Reproduction1h 2m
- Animal Reproduction
  1h 2m
45. Nervous System1h 55m
- Neurons and Action Potentials
  1h 8m
- Central and Peripheral Nervous System
  46m
46. Sensory Systems46m
- Sensory System
  46m
47. Muscle Systems23m
- Musculoskeletal System
  23m
48. Ecology3h 11m
49. Animal Behavior28m
- Animal Behavior
  28m
50. Population Ecology3h 41m
51. Community Ecology2h 46m
52. Ecosystems2h 36m
53. Conservation Biology24m
- Conservation Biology
  24m

37. Plant Sensation and Response

Phototropism

General Biology

37. Plant Sensation and Response

Phototropism

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1:48 minutes

Problem 4

Textbook Question

How may a plant respond to severe heat stress?
a. By reorienting leaves to increase evaporative cooling
b. By creating air tubes for ventilation
c. By producing heat-shock proteins, which may protect the plant's proteins from denaturing
d. By increasing the proportion of unsaturated fatty acids in cell membranes, reducing their fluidity

Verified step by step guidance

Understand that plants, like all organisms, have mechanisms to cope with environmental stress, including heat stress.

Recognize that heat stress can cause proteins to denature, which can disrupt cellular functions.

Learn that one common response to heat stress in plants is the production of heat-shock proteins. These proteins help stabilize and refold denatured proteins, protecting the plant's cellular machinery.

Consider the role of leaf orientation in temperature regulation. By reorienting leaves, plants can reduce direct sunlight exposure and increase evaporative cooling, which helps in temperature regulation.

Evaluate the role of cell membrane composition. Increasing the proportion of unsaturated fatty acids generally increases membrane fluidity, not reduces it, which helps maintain membrane function under stress conditions.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Heat Stress in Plants

Heat stress in plants occurs when temperatures exceed a plant's optimal range, potentially leading to cellular damage and impaired physiological functions. Plants have evolved various mechanisms to cope with heat stress, such as altering leaf orientation, producing protective proteins, and adjusting membrane composition to maintain cellular integrity and function.

Heat-Shock Proteins

Heat-shock proteins (HSPs) are a group of proteins produced by plants in response to elevated temperatures. They function as molecular chaperones, stabilizing and refolding denatured proteins, thus preventing aggregation and maintaining cellular homeostasis. This protective mechanism is crucial for plant survival under heat stress conditions.

Membrane Fluidity and Fatty Acids

The fluidity of cell membranes is influenced by the composition of fatty acids in the lipid bilayer. Unsaturated fatty acids increase membrane fluidity, while saturated fatty acids decrease it. In response to heat stress, plants may adjust the proportion of unsaturated fatty acids to maintain optimal membrane fluidity, ensuring proper cellular function and stability.

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Related Practice

Textbook Question

Auxin enhances cell elongation in all of these ways except:

a. Increased uptake of solutes

b. Gene activation

c. Acid-induced denaturation of cell wall proteins

d. Cell wall loosening

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views

Textbook Question

Which of the following statements about phytochrome is not correct?

a. It is photoreversible.

b. Its function was understood long before the protein itself was isolated.

c. The Pfr form activates the responses to red light.

d. It is involved in guard-cell opening.

780

views

Textbook Question

Charles and Francis Darwin discovered that

a. Auxin is responsible for phototropic curvature

b. Red light is most effective in shoot phototropism

c. Light destroys auxin

d. Light is perceived by the tips of coleoptiles

Auxin causes a shoot to bend toward the light by

a. Causing cells to shrink on the dark side of the shoot

b. Stimulating growth on the dark side of the shoot

c. Causing cells to shrink on the lighted side of the shoot

d. Stimulating growth on the lighted side of the shoot

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Textbook Question

The signaling molecule for flowering might be released earlier than usual in a long-day plant exposed to flashes of:

a. Far-red light during the night

b. Red light during the night

c. Red light followed by far-red light during the night.

d. Far-red light during the day

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Textbook Question

If a long-day plant has a critical night length of 9 hours, which 24-hour cycle would prevent flowering?

a. 16 hours light/8 hours dark

b. 14 hours light/10 hours dark

c. 4 hours light/8 hours dark/4 hours light/8 hours dark

d. 8 hours light/8 hours dark/light flash/8 hours dark

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Textbook Question

Phytochromes can be considered 'shade detectors,' while phototropins such as PHOT1 can be considered 'sunlight detectors.' Explain why these characterizations are valid.

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Textbook Question

In general, small seeds that have few food reserves must be exposed to red light before they will germinate. (Lettuce is an example.) In contrast, large seeds that have substantial food reserves typically do not depend on red light as a stimulus to trigger germination. State a hypothesis to explain these observations.

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