Explanation:

The source of food for a seed that has not grown its leaves is the stored food within the seed itself.

When a seed is formed, it contains all the necessary nutrients and energy required for the growth of a new plant. These nutrients are stored in the form of food reserves within the seed. The stored food provides energy for the seed to germinate and grow until it can produce its own food through photosynthesis.

Stored Food Reserves in Seeds:

Seeds contain different types of stored food reserves depending on the plant species. The three main types of stored food reserves found in seeds are:

1. Endosperm: In some seeds, the food reserves are stored in a tissue called endosperm. Endosperm is rich in starch, proteins, and oils. During germination, the endosperm provides nourishment to the developing seedling until it can produce its own food.

2. Cotyledons: In other seeds, the food reserves are stored in thick, fleshy structures called cotyledons. Cotyledons are often referred to as seed leaves. They are packed with nutrients like starch, proteins, and oils. During germination, the cotyledons provide nourishment to the growing seedling.

3. Embryo: In addition to endosperm or cotyledons, the embryo itself also contains some stored food reserves. These reserves are mainly in the form of oils. The embryo is the young plant within the seed, and it uses the stored food to grow until it can establish roots and absorb nutrients from the soil.

Utilization of Stored Food:

When a seed germinates, it absorbs water and swells. This triggers metabolic processes within the seed, and enzymes are activated. These enzymes break down the stored food reserves into simpler forms such as sugars, amino acids, and lipids. These simpler forms of nutrients are then transported to the growing regions of the seedling, where they are utilized for energy and growth.

As the seedling grows, it develops roots that can absorb water and nutrients from the soil. Once the seedling has grown its leaves and established itself, it starts producing its own food through photosynthesis. The stored food reserves within the seed are depleted and are no longer needed.

So, until the seed has grown its leaves, it relies on the stored food reserves within the seed itself for its source of food.