Plants like beans have two fleshy structures in their seeds. These structures are called cotyledons and their main function during germination is to:

Cotyledons, also known as seed leaves, play a crucial role during the germination process of plants like beans. Here's how they function, step by step:

1. Seed Dormancy: The cotyledons remain inside the seed in a dormant state, storing food and nutrients necessary for the growth of the embryo plant.

2. Absorption of Water: When the seed is sown and watered, it absorbs water and swells. This breaks the seed coat and signals the start of germination.

3. Food Supply: The cotyledons, rich in starch and proteins, start to provide the necessary nutrients to the growing embryo. This energy is used for the growth of the root (radicle) and shoot (plumule).

4. Photosynthesis: Once the shoot reaches the surface and the plant is exposed to sunlight, the cotyledons may also perform photosynthesis to produce more food until the true leaves develop and take over this function.

5. Degradation: After the true leaves have developed and the plant can sustain itself, the cotyledons have fulfilled their purpose and will shrivel up and fall off.

So, in summary, the main function of cotyledons during germination is to supply the germinating seed with food and nutrients until it can produce its own through photosynthesis.