Question

Synthetic plant hormone is
(a) IAA
(b) 2,4-D/NAA
(c) GA
(d) Zeatin

Answer 1

Hint: Plant hormones (also known as phytohormones) are signal molecules that exist at extremely low concentrations and are formed within plants. A synthetic plant hormone in the auxin family promotes flowering in pineapple and is an ingredient in many commercial plants rooting horticultural products.

Complete answer:
A synthetic auxin that is produced is naphthalene acetic acid (NAA). It assists in the pineapple flowering process. It is soluble in organic solvents and is an organic compound that is a colorless solid. It has a naphthalene's "1-position" which is attached to the group of carboxymethyl.
The hormone NAA occurs artificially instead of naturally, and when present at high concentrations like all auxins then it is toxic to plants. It is a rooting agent and from stem and leaf cuttings it is used for the vegetative propagation of plants. It is also during the process of the tissue culture of plants. Auxins are used when cutting plants to stimulate root development especially 1-naphthaleneacetic acid (NAA) and indole-3-butyric acid (IBA).
2, 4-D (2, 4-dichlorophenoxyacetic acid) is also synthetic auxins. The oldest auxin which is known to be commercially available since 1945 is 2,4-D and is also the most available herbicide in the world. Its patent thereon had expired long ago so it is now produced by many chemical companies. It is used as a weedkiller for various cereal crops that includes orchards and pastures. It is found in more than 1,500 herbicide products.

So, the correct answer is option b)‘2,4-D/NAA’

Note:
Auxin is a phytohormone produced within the stem tip that promotes cell elongation. Auxin will move to the darker side of the plant i.e part receiving less sunlight, causing the cells there to grow larger than corresponding cells on the lighter side of the plant. They help in the process of development of buds, cell enlargement, and initiation of roots.