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GATE 2024 BT Q.49: solution and answer

GATE 2024 · BTQ.49 · 2 marks · MSQ

Which of the following is/are synthetic auxin(s) that does/do NOT occur naturally?

  1. (A)

    2,4-Dichlorophenoxyacetic acid

  2. (B)

    Indole-3-acetic acid

  3. (C)

    Indole-3-butyric acid

  4. (D)

    1-Naphthaleneacetic acid

See the question in the paper
GATE 2024 BT question 49Tap to open full size

Answer and solution

ANSWER

The synthetic auxins that do not occur naturally are (A) 2,4-D and (D) NAA.

Official answer: A, DSource: Official answer key, GATE 2024 BT (IISc Bengaluru)

  1. The question asks for auxins that are man-made and never found in plants, so each option is checked for natural occurrence.

  2. (A) 2,4-Dichlorophenoxyacetic acid (2,4-D) is a synthetic auxin. It is a phenoxy compound that plants do not make. It is correct.

  3. (B) Indole-3-acetic acid (IAA) is the main natural auxin. Plants make it from tryptophan. It is wrong.

  4. (C) Indole-3-butyric acid (IBA) is used as a rooting hormone, but it has also been isolated from maize, Arabidopsis and other plants. It is an endogenous auxin, so it is wrong.

  5. (D) 1-Naphthaleneacetic acid (NAA) is a synthetic auxin. Plants do not make it, and it is used in tissue culture for rooting and callus. It is correct.

  6. The synthetic auxins that do not occur naturally are 2,4-D and NAA, which gives A and D.

KEY IDEA

Natural auxins are IAA and the endogenous IBA, along with a few others such as 4-chloroindole-3-acetic acid and phenylacetic acid. 2,4-D and NAA are purely synthetic auxins.

WATCH OUT FOR

Treating IBA as synthetic because it is sold as a commercial rooting powder. It has been isolated from maize and Arabidopsis, so it occurs naturally.

From the GATE 2024 BT paper. Every question of this paper · Download the full paper · All 8 Plant tissue culture questions, with notes

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