Read the following statements regarding the plant growth regulator first isolated by F.W. Went from the tips of oat coleoptiles: I. It was first isolated from human urine. II. It promotes apical dominance in higher plants. III. NAA and 2,4-D are its natural derivatives isolated from plants. IV. It is widely used to kill monocotyledonous weeds. How many of the above statements are correct?

Step-by-step solution

The plant growth regulator first isolated by F.W. Went from the tips of oat (Avena) coleoptiles is auxin. Statement I is correct: Auxin was first isolated from human urine. Statement II is correct: In higher plants, the growing apical bud inhibits the growth of lateral (axillary) buds, a phenomenon called apical dominance, which is mediated by auxins. Statement III is incorrect: IAA and IBA are natural auxins isolated from plants, whereas NAA and 2,4-D are synthetic auxins. Statement IV is incorrect: 2,4-D is widel