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

Reason: The ‘bakanae’ (foolish seedling) disease of rice seedlings, was caused by a bacterial pathogen Gibberella fujikuroi.

Assertion is true but reason is false.

The correct answer is Option (3)- Assertion is true but reason is false.

The five major groups of PGRs have been accidental. All this started with the observation of Charles Darwin and his son Francis Darwin when they 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. The ‘bakanae’ (foolish seedling) disease of rice seedlings, was caused by a fungal pathogen Gibberella fujikuroi.

E. Kurosawa (1926) reported the appearance of symptoms of the disease in rice seedlings when they were treated with sterile filtrates of the fungus. The active substances were later identified as gibberellic acid.