Question 1

Which of the following best explains why some legumes lower their leaves in the evening and raise them in the morning, even when kept under constant light or dark conditions?

Accepted Answer

They are governed by an internal circadian clock.

Question 2

A plant’s circadian rhythm can be entrained to exactly 24 hours by the day/night cycle. Which molecular mechanism is most likely involved in this process?

Accepted Answer

Negative feedback loops regulating protein synthesis.

Question 3

Which photoreceptor is most effective in marking sunrise and sunset for the plant’s biological clock?

Accepted Answer

Phytochromes.

Question 4

A short-day plant is exposed to a long night, but a flash of red light interrupts the night. What is the likely outcome?

Accepted Answer

The plant will not flower.

Question 5

Which equation best represents the water potential ($$\Psi) of a $$plant cell, considering solute and pressure components?

Accepted Answer

$$\Psi = \Psi_s + \Psi_p$$

Question 6

Which hormone is produced in response to flooding and helps create air tubes in roots?

Accepted Answer

Ethylene

Question 7

What is the primary physiological response of plants to salt stress?

Accepted Answer

Producing solutes tolerated at high concentrations.

Question 8

Which protein is produced by plants to protect other proteins from denaturing during heat stress?

Accepted Answer

Heat-shock protein

Question 9

How do frost-tolerant plants reduce water loss in response to freezing?

Accepted Answer

By increasing the concentration of nontoxic solutes inside their cells.

Question 10

Which of the following is a real-world example of thigmotropism?

Accepted Answer

Tendrils of climbing plants coiling around a support.

Question 11

Which mechanism allows plants to detect gravity?

Accepted Answer

The settling of statoliths in root cap cells.

Question 12

What is the function of florigen in plants?

Accepted Answer

It induces flowering in both short-day and long-day plants.

Question 13

Which of the following is NOT a defense mechanism plants use against herbivores?

Accepted Answer

Increasing membrane fluidity.

Question 14

What is the main difference between PAMP-triggered immunity and effector-triggered immunity in plants?

Accepted Answer

PAMP-triggered immunity is activated by pathogen-associated molecular patterns, while effector-triggered immunity is activated by specific pathogen effectors.

Question 15

Systemic acquired resistance in plants involves the movement of which signaling molecule from the infection site to remote areas?

Accepted Answer

Methylsalicylic acid

Question 16

Which equation best describes the relationship between membrane fluidity and temperature in plants?

Accepted Answer

$$F \propto T$$

Question 17

A plant exposed to drought closes its stomata. What is the most immediate effect on the plant’s physiology?

Accepted Answer

Reduced transpiration and water loss.

Question 18

Which of the following best describes the hypersensitive response in plants?

Accepted Answer

Localized tissue death near the infection site to restrict pathogen spread.

Question 19

Which environmental stress is most likely to cause denaturation of plant enzymes, as shown in the provided image?

Accepted Answer

Heat stress

Question 20

Which of the following statements about antifreeze proteins in plants is correct?

Accepted Answer

They prevent the formation of ice crystals and have evolved through convergent evolution.

Plant Responses to Internal and External Signals: Biological Clocks, Environmental Stimuli, and Stress Adaptations

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