Wheat seedlings. Seedlings of wheat, Triticum sp. , growing in humus soil. The soil has been cross- sectioned and shows the roots and seed cases of the seedlings. The seeds contain all the nutrients needed by the seedling to grow until it can make its own food. The seedling makes food by photosynthesis in the green shoots whilst using its roots to gather water and nutrients from the soil. Humus soil is rich in decaying organic matter which releases nutrients that are essential to plant growth.