Assertion (A): The discovery of plant growth regulators (PGRs) began with Charles Darwin and his son Francis Darwin observing phototropism in canary grass coleoptiles.
Reason (R): F.W. Went isolated auxin from the tips of oat seedling coleoptiles, proving that the tip was the site of a substance influencing growth direction.

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Both A and R are true, and R is the correct explanation of A.

Both A and R are true, but R is not the correct explanation of A.

A is true, but R is false.

A is false, but R is true

answer is B.

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Detailed Solution

Charles Darwin and his son Francis Darwin observed that the coleoptiles of canary grass responded to unilateral illumination by growing towards the light source (phototropism).

After a series of experiments, it was concluded that the tip of coleoptile was the site of transmittable influence that caused the bending of the entire coleoptile.

Auxin was isolated by F.W. Went from tips of coleoptiles of oat seedlings.

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