Q41
Which one of the following pairs is not correctly matched?
Correct Answer
Option A
Solution
(a) Gibberellic acid causes cell elongation, not leaf fall. Leaf fall is controlled by ABA.
Plant Growth and Development
Q42
Which one of the following acids is a derivative of carotenoids?
Correct Answer
Option C
Solution
(c) ABA is derived from carotenoids (xanthophyll pathway).
Q43
One of the synthetic auxins is
Correct Answer
Option D
Solution
(d) NAA (naphthaleneacetic acid) is a synthetic auxin.
Q44
Phototropic curvature is the result of uneven distribution of
Correct Answer
Option D
Solution
(d) Uneven auxin distribution causes differential cell elongation leading to phototropic bending.
Q45
Which one of the following generally acts as an antagonist to gibberellins?
Correct Answer
Option C
Solution
(c) ABA antagonizes gibberellins — e.g., inhibits alpha-amylase induction in barley.
Q46
The pineapple which is difficult to blossom under natural conditions has been made to produce fruits throughout the year by application of
Correct Answer
Option B
Solution
(b) NAA and 2,4-D (synthetic auxins) induce flowering in pineapple throughout the year.
Q47
Which one of the following growth regulators is known as stress hormone?
Correct Answer
Option A
Solution
(a) ABA is called the stress hormone — induces stomatal closure under water stress.
Q48
A few normal seedlings of tomato kept in dark room for a few days became white-coloured. This is termed
Correct Answer
Option C
Solution
(c) Etiolation: pale, elongated growth in darkness due to absence of light.
Q49
Auxin can be bioassayed by
Correct Answer
Option D
Solution
(d) Avena coleoptile curvature test (Went, 1928) is the standard auxin bioassay.
Q50
What causes a green plant exposed to light on only one side to bend toward the light source?
Correct Answer
Option C
Solution
(c) Auxin migrates to the shaded side, causing greater elongation there and bending toward light.
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