Question 1

Which of the following best describes the process of photomorphogenesis in plants?

Accepted Answer

A nondirectional, light-triggered developmental process.

Question 2

A plant is exposed to red light, which converts phytochrome from its inactive form ($P_r$) to its active form ($P_{fr}$). What is a likely physiological response?

Accepted Answer

Stimulation of seed germination.

Question 3

Which plant hormone is primarily responsible for promoting cell elongation on the shaded side of a seedling, resulting in phototropic bending toward light?

Accepted Answer

Auxin

Question 4

A mutant plant is unable to synthesize gibberellins. Which of the following phenotypes would you expect?

Accepted Answer

Short, dwarf stems

Question 5

Which of the following best explains why roots exhibit positive gravitropism?

Accepted Answer

Roots grow toward gravity because auxin inhibits cell elongation on the lower side.

Question 6

Which hormone is synthesized mainly in mature green leaves and is essential for inducing seed dormancy and closing stomata during drought?

Accepted Answer

Abscisic acid

Question 7

A plant is exposed to blue light on one side. Which receptor is primarily responsible for detecting this light and initiating phototropic bending?

Accepted Answer

Phototropin 1 (PHOT1)

Question 8

Which of the following is a correct sequence for a typical signal transduction pathway in plants?

Accepted Answer

Reception → Transduction → Response

Question 9

Which hormone is known to inhibit axillary bud growth, thus affecting the extent of branching in plants?

Accepted Answer

Strigolactones

Question 10

A plant tissue culture experiment varies the ratio of auxin to cytokinin. Which outcome is most likely if the cytokinin concentration is much higher than auxin?

Accepted Answer

Formation of shoots

Question 11

Which of the following best describes the role of oligosaccharins in plant defense?

Accepted Answer

They are released from the cell wall by pathogens and signal defense responses.

Question 12

Which of the following is a real-world application of gibberellins in agriculture?

Accepted Answer

Used to extend internode length in grapes, resulting in larger fruit.

Question 13

Which of the following best explains why a potato grown in the dark appears pale and elongated, but turns green and develops leaves when exposed to light?

Accepted Answer

Etiolation occurs in the dark, and de-etiolation (greening) is triggered by light-induced activation of phytochrome.

Question 14

Which of the following is a function of brassinosteroids in plants?

Accepted Answer

They promote cell elongation, vascular tissue development, and delay senescence.

Question 15

A scientist applies auxin to the cut surface of a plant stem. What is the most likely outcome?

Accepted Answer

Promotion of root formation at the cut surface.

Question 16

Which of the following best describes the interaction between auxin and cytokinin in regulating plant tissue differentiation?

Accepted Answer

High auxin and low cytokinin promote root formation; high cytokinin and low auxin promote shoot formation.

Question 17

Which of the following is a direct effect of abscisic acid (ABA) on guard cells during drought conditions?

Accepted Answer

ABA promotes the movement of potassium ions out of guard cells, leading to stomatal closure.

Question 18

Which of the following best explains why lettuce seeds exposed to far-red light after red light fail to germinate?

Accepted Answer

Far-red light converts phytochrome to its inactive form ($P_r$), inhibiting germination.

Question 19

Which of the following is a plausible outcome if a plant is infected by Agrobacterium that inserts genes for increased cytokinin and auxin production?

Accepted Answer

Formation of a crown gall tumor due to massive cell division.

Question 20

Which of the following best describes the effect of blue light on stomatal opening?

Accepted Answer

Blue light is detected by zeaxanthin, which triggers stomatal opening.

Plant Development and Hormonal Control: Environmental and Internal Regulation

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