Question

Describe an experiment which demonstrates that growth stimulating hormone is produced at the tip of coleoptile.

[Review question: Pg. No: 241]

Answer 1

Frits Warmolt Went (1903 – 1990), a Dutch biologist demonstrated the ,existence and effect of auxin in plants. He did a series of experiments in , Avena coleoptiles.

1. In his first experiment he removed the tips of Avena coleoptiles.
2. he cut tips did not grow indicating that the tips produced something essential for growth.
3. In his second experiment he placed the agar blocks on the decapitated coleoptile tips.
4. The coleoptile tips did not show any response. In his next experiment he placed the detached coleoptile tips on agar blocks.
5. After an hour, he discarded the tips and placed this agar block on the decapitated coleoptile.
6. It grew straight up indicating that some chemical had diffused from the cut coleoptile tips into the agar block which stimulated the growth.

From his experiments went concluded that a chemical diffusing from the tip of coleoptiles was responsible for growth and he named it as “Auxin” meaning “to grow”.