A barley mutant lacking a gibberellic acid receptor would
a. Fail to make GA.
b. Catalyze starch more quickly.
c. Fail to make α-amylase.
d. Fail to take up water.

Verified step by step guidance

Understand the role of gibberellic acid (GA) in plants: GA is a plant hormone that plays a crucial role in various growth processes, including seed germination, stem elongation, and enzyme production.

Recognize the function of a gibberellic acid receptor: This receptor is necessary for the plant to respond to GA. When GA binds to its receptor, it triggers a signaling pathway that leads to specific physiological responses.

Identify the process of seed germination: During germination, GA stimulates the production of enzymes like alpha-amylase, which breaks down starches into sugars to provide energy for the growing seedling.

Consider the consequences of lacking a GA receptor: Without the receptor, the plant cannot respond to GA, which means it cannot initiate the signaling pathway necessary for producing enzymes like alpha-amylase.

Evaluate the options: Since the mutant lacks the receptor, it would specifically fail to produce alpha-amylase, as this process is directly dependent on GA signaling. Therefore, the correct answer is related to the failure in enzyme production.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Gibberellic Acid (GA)

Gibberellic acid is a plant hormone that plays a crucial role in various growth processes, including seed germination, stem elongation, and enzyme production. It is essential for the synthesis of enzymes like α-amylase, which helps in breaking down starch into sugars during seed germination. Understanding GA's function is key to analyzing the effects of its receptor absence.

Gibberellic Acid Receptor

The gibberellic acid receptor is a protein that binds to GA, initiating a signal transduction pathway that leads to physiological responses such as enzyme production and growth regulation. Without this receptor, the plant cannot respond to GA, affecting processes like α-amylase synthesis, which is vital for starch breakdown during germination.

α-Amylase

α-Amylase is an enzyme that catalyzes the hydrolysis of starch into sugars, providing energy for the growing plant. Its production is stimulated by gibberellic acid during seed germination. A lack of GA receptor would impede α-amylase synthesis, affecting the plant's ability to utilize stored starch, which is crucial for early growth stages.

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