An enzyme which can stimulate the germination of barley seeds is

The correct option is α-amylase.

Here is a step-by-step explanation of why α-amylase stimulates the germination of barley seeds:

1. Role of Gibberellin (Plant Hormone):
During the germination of barley seeds, the embryo releases a plant hormone called gibberellic acid (GA). This hormone diffuses into the aleurone layer (the outer protein-rich layer surrounding the endosperm) of the seed.

2. De Novo Synthesis of α-amylase:
In response to gibberellic acid, the cells of the aleurone layer are stimulated to synthesize and secrete hydrolytic enzymes, most notably α-amylase.

3. Hydrolysis of Starch:
Barley endosperm serves as a major food reserve, storing energy primarily in the form of starch. Once α-amylase is secreted into the endosperm, it breaks down the insoluble starch molecules (amylose and amylopectin) into soluble sugars like maltose and glucose.

4. Nourishing the Embryo:
These simple, soluble sugars are easily transported to the growing embryo, providing the essential energy and carbon skeletons required for cellular respiration, growth, and successful seedling establishment. Thus, the enzyme α-amylase plays a critical, rate-limiting role in stimulating and driving the germination process of barley seeds.