Question

The hormone which signals the closure of stomata is??​

Answer 1

abscisic acid

Among these, abscisic acid (ABA), is the best-known stress hormone that closes the stomata, although other phytohormones, such as jasmonic acid, brassinosteroids, cytokinins, or ethylene are also involved in the stomatal response to stresses.

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Answer 2

The plant hormone that signals the closure of  stomata is abscisic acid

What is Abscisic Acid?

• Also known as Stress hormone.
• It is a plant hormone
• Also written as ABA
• Chemical formula of ABA is $\tt C_{15}H_{20}O_4$.

Functions of ABA

• Inhibits shoot growth
• Help in development and maturation of seed
• Close stomata in the lack of water. To slow down the process of Transpiration.