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Assertion :- The first phytohormone to be discovered was auxin.
Reason :- light reaction of coleoptile tip attracted the attention of Darwin in the last quarter of the nineteenth century.
A.Both assertion and reason are correct and reason is the correct explanation of assertion.
B.Both assertion and reason are correct but reason is not the correct explanation of assertion.
C.Assertion is correct but reason is incorrect.
D.Both assertion and reason are incorrect

Last updated date: 25th Jun 2024
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Hint: Plant hormones are the chemical substance that is produced by the plants itself to support the growth and development of the plants, these hormones are also known as the phytohormone.

Complete answer:
1.One of the most renowned scientists Fritz performs an experiment on oat seedlings regarding the effect of the phytohormone further named as auxin hormone.
2.Darwin also contributed to the discovery of the first phytohormone known as auxin.
The auxin is named as auxin 5 year after the discovery of the hormone.
3.One of the most famous scientists names as Darwin performed an experiments on coleoptiles of the canary grass and observe that the plant shows it’s unidirectional growth towards the source of the light and it bends towards the source from where light is coming
4.He thought that the coleoptile of the canary grass is sensitive towards the sunlight and after that it convey message downward to the plant which cause bending of the canary grass towards the light
5.This shows the positive phototropism in the plant and we can conclude that the sunlight is one of the main components for growth of the plants.

Here both assertion and reason are correct but reason is not the correct explanation of the assertion.

Hence the correct answer is OPTION(B)

Note: 1.Auxin hormone is responsible for the upward growth of the plants and increase the height of the plant.
2.It is most essential for the growth of the plants.
3.It also regulates the behaviour of the plant life cycle.