Question

Which of the following is not a natural auxin?
a. Indole acetic acid
b. Naphthalene acetic acid
c. Indole acetaldehyde
d. Indole ethanol

Answer 1

Hint: Auxins are the class of plant hormones, where they play an important role in the life cycle of plants, for their growth and development, and these auxins are useful to plant body development and behavioral process, and these auxins have Morphogen like characteristics.

Complete answer:
The first isolated phytohormone in plants is indole-3-acetic acid.
> Totally there are 5 endogenous produced natural auxins that occur in plants, which include.
- Indole-3-acetic acid.
- 4-Chloroindole-3 acetic acid.
- Phenylacetic acid
- Indole-3-butyric acid
- Indole-3-propanoic acid.

> Some of the examples of synthetic auxins are
- 2,4 Dichlorophenoxy acetic acid.
- Naphthalene acetic acid
- Methoxy 3,6 dichlorobenzoic acid.

> Functions of auxins:
- They show phototropism and geotropism.
- They stimulate cell elongation in plants, mainly by cell wall loosening factors, such as elastins.
- The effect of auxins is high; they have the presence of gibberellins also.
- They induce rooting in very high concentrations.
- Auxins have a function of accumulation, where they induce sugar and mineral accumulation.
- In the case of any wounds that occur to the plants, auxins Induce cell differentiation.
- Auxins show the root initiation, and they also induce apical dominance in plants.
- Auxins help for the growth and development of fruits, and they delay the fruit senescence.
- They also play a minor role in flower initiation.

Hence, the correct answer is option (B).

Note: The presence of Auxins in very large concentration, is not good for the plants, and the presence of high concentration is more toxic to the dicots and less toxic go the monocots, so because of this purpose, synthetic auxin herbicides have been developed and they use for weed control.