Question

The phytohormone which induces triple response is ...............

• A. IAA
• B. ABA
• C. GA${}_3$
• D. $C_2{H}_4$

Answer 1

The correct option is D $C_2{H}_4$

Triple response is the peculiar characteristic of ethylene. Germinating seedlings synthesize ethylene when their growth is impeded by the soil. The ethylene promotes the so - called 'triple response' : an exaggeration of the transient developmental structure known as the apical hook, together with the inhibition of hypocotyl and root extension growth. The triple response is thought to protect the shoot and root apical meristems from damage during growth throughout the soil.