Question 1

Which of the following best describes the process by which plants detect and respond to environmental stimuli?

Accepted Answer

Plants use signal transduction pathways, where a receptor detects a stimulus, transduces it into an internal signal, and initiates a response in target cells.

Question 2

A plant bends toward a window where sunlight is coming in. Which hormone is primarily responsible for this phototropic response, and how does it work?

Accepted Answer

Auxin; it accumulates on the shaded side of the stem, causing those cells to elongate more and the stem to bend toward the light.

Question 3

Which of the following statements about phytochromes is correct?

Accepted Answer

Phytochromes exist in two forms, $$P_r$$ and $$P_{fr}$$, and can switch between these forms in response to red and far-red light.

Question 4

A scientist exposes lettuce seeds to the following sequence of light: Red $$ightarrow$$ Far-Red $$ightarrow$$ Red. According to the photoreversibility hypothesis, what is the expected outcome for seed germination?

Accepted Answer

High germination rate, because the last exposure was to red light, which promotes germination.

Question 5

Which of the following best explains why shoots exhibit negative gravitropism?

Accepted Answer

Auxin redistributes to the lower side of the shoot, causing those cells to elongate more and the shoot to bend upward, away from gravity.

Question 6

Which of the following is NOT a typical plant response to herbivory?

Accepted Answer

Increased uptake of carbon dioxide to escape herbivores.

Question 7

A Venus flytrap closes its leaves rapidly when an insect touches its sensory hairs. What type of signal transduction is primarily involved in this response?

Accepted Answer

Electrical signals (action potentials) generated by the touch are transduced into a rapid movement response.

Question 8

Which of the following best describes the role of second messengers in plant signal transduction?

Accepted Answer

They amplify the signal inside the cell, leading to a larger cellular response.

Question 9

A plant is exposed to wind and responds by growing shorter and sturdier. What is this phenomenon called?

Accepted Answer

Thigmomorphogenesis

Question 10

Which of the following is a correct sequence of events in plant information processing?

Accepted Answer

Stimulus detected by sensory cell $$\rightarrow$$ Signal transduction $$\rightarrow$$ Hormone released $$\rightarrow$$ Target cell response

Question 11

Which of the following best explains why far-red light inhibits seed germination?

Accepted Answer

Far-red light converts phytochrome to the $$P_r$$ form, which is inactive for promoting germination.

Question 12

A plant root grows toward a source of water. What is this response called, and what is the likely mechanism?

Accepted Answer

Hydrotropism; roots detect moisture gradients and grow toward higher water concentrations.

Question 13

Which of the following is a real-world application of understanding plant sensory systems?

Accepted Answer

Developing crops that are more resistant to drought by manipulating root signaling pathways.

Question 14

Which of the following best describes the function of trichomes in plant defense?

Accepted Answer

Trichomes are specialized epidermal cells that can physically deter herbivores and sometimes release irritating chemicals.

Question 15

A plant is exposed to a sequence of red, far-red, and then red light. According to the data on lettuce seed germination, what is the expected germination percentage?

Accepted Answer

100%

Question 16

Which of the following is an example of thigmotropism?

Accepted Answer

A vine wrapping around a trellis after making contact with it.

Question 17

Which of the following best explains the concept of apical dominance in plants?

Accepted Answer

The apical bud produces auxin, which suppresses the growth of lateral (axillary) buds.

Question 18

Which of the following is a correct statement about photoperiodism in plants?

Accepted Answer

Flowering is triggered by the length of night, not the length of daylight.

Question 19

Which of the following is a plausible reason why plants have evolved both mechanical and chemical defenses against herbivores?

Accepted Answer

Mechanical defenses provide a physical barrier, while chemical defenses deter or harm herbivores that breach the barrier.

Plant Sensory Systems: Signals and Responses

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