Question:

One of the synthetic auxin is

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All these auxins are extensively used in agricultural and horticultural practices

Updated On: Aug 20, 2024
  • IAA
  • NAA
  • IBA

  • both B and C

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The Correct Option is B

Solution and Explanation

NAA (Naphthalene Acetic Acid) is a synthetic plant hormone in the auxin family. It is used as an ingredient in many commercial plants rooting horticultural products. 

  • NAA and 2,4-D (2.4-dichloro phenoxy acetic acid) are both synthetic auxins. 
  • IAA and IBA (Indole Butyric Acid) are isolated from plants. 
  • NAA does not occur naturally and is toxic to plants at high concentrations. 

Therefore, B) NAA is the correct answer.

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Concepts Used:

Plant Growth Regulators

What is a plant growth regulator?

Plant growth regulators (PGRs) are chemicals used to modify plant growth such as increasing branching, suppressing shoot growth, increasing return bloom, removing excess fruit, or altering fruit maturity.

Types of Plant Growth:

There are the following types of plant growth.

  • Primary and Secondary Growth: The growth of a plant is termed primary when the same happens through the mitotic division of the meristematic cells which are present at the root and the shoot of the plants. 

Whereas, the secondary growth in a plant takes place through the division of the secondary meristem, which, in turn increases the diameter of the body of the plants.

  • Primary and Secondary Plant Growth
  • Unlimited Growth
  • Limited Growth
  • Vegetative Growth
  • Reproductive Growth

The five groups of plant growth regulators used in fruit crops include:

  1. Auxins: Auxins are one of the most important plant hormones. The chief naturally occurring auxin is indole-3 acetic acid – IAA and other related compounds.
  2. Gibberellins: Gibberellins are an extensive chemical family based on the ent-gibberellane structure. The first gibberellin to be discovered was gibberellic acid. Now there are more than 100 types of gibberellins.
  3. Cytokinins: These are produced in the regions where cell division occurs; mostly in the roots and shoots. They help in the production of new leaves, lateral shoot growth, chloroplasts in leaves etc.
  4. Absicisic Acid: Absicsic acid controls the dormancy of buds and seeds, inhibits shoot growth and is involved in regulating water loss from plants.
  5. Ethylene: Ethylene is a simple, gaseous plant growth regulator, synthesised by most of the plant organs includes ripening fruits and ageing tissues.