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Solved Examples on Plant Growth and Development

Question1: One of the synthetic auxin is [CBSE PMT’2009]

(a) IAA

(b) GA

(c) IBA

(d) NAA

Answer: d


NAA is a synthetic auxin. Some of the most widely used weed killers are synthetic auxins. Synthetic auxin analogs include 1-naphthaleneacetic acid (NAA), 2,4-dichlorophenoxy acetic acid (2,4-D) and 2,4,5-trichlorophenoxy acetic acid (2,4,5-T).

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Question2: Which one of the following acids is a derivative of carotenoids? [CBSE PMT’2009]

(a) IAA

(b) GA

(c) Abscisic acid

(d) IBA

Answer: c


ABA also known as abscisin II and dormin is a plant hormone. It functions in many plant developmental processes, including bud dormancy. ABA is a derivative of carotenoids. It was called abscisin II originally because it was thought to play a major role in abscisision of fruits. At about the same time another group was calling it ‘dormin’ because they thought it had a major role in bud dormancy. The name ABA was coined by a compromise between the two groups.

Question3: Phototrophic curvature is the result of uneven distribution of [CBSE PMT’2010]

(a) Gibberellin

(b) Phytochrome

(c) Cytokinins

(d) Auxin

Answer: d


Phototrophic curvature is the result of uneven distribution of auxin. The experiments conducted by Charles Darwin concluded that the tip of coleoptile of canary grass contain auxin that causes the bending of the entire coleoptiles towards the light source.