Phaseolus vulgaris is the scientific name for "common bean." It is an herbaceous annual plant grown for its edible beans. The common bean has been cultivated in the Americas for 6,000 years. It is prized for its high protein content, carbohydrates and iron. Some common bean types are soybeans, kidney beans, pinto beans and garden peas. Beans are also known as "legumes." Seeds are what the bean plant uses to propagate itself.
Seeds of the common bean are plump with a kidney or oval shape. Bean seeds come in a variety of colors from white to red to black. Some bean seeds are two colors and mottled looking. The seeds have a slight indentation along one side called the micropyle where moisture enters. A bean can remain dormant for a long time, waiting for moisture, sunlight and soil to begin its life cycle.
The seed's outer coating is called the testa, and it protects the soft inner portions of the seed. It is thin but also hard and is sometimes rough and creased. On the testa there is a scar called the hilum, where the bean was attached to the bean pod. The bean pod is sometimes called the fruit of the plant.
The new plant inside the seed is called the embryo. There is just enough moisture in the testa to keep the embryo material alive until germination. Germination begins in the micropyle, which is next to the hilum. Seeds can stay dormant for a long time, waiting for the correct external conditions to begin their growth cycle.
Beans seeds are dicot or dicotyledon. A dicot bean is one that has two cotyledons. These are two food-storage structures called the radicle and the pumule. The radicle is the first root of the plant; the pumule is the first shoot that grows. Both structures contain food that gives energy to the seed when it germinates. The pumule has two very tiny leaves.
Hypocotyl and Epicotyl
Between the root and the cotyledons is an area called the hypocotyl. When the bean becomes moist and begins to transform into a bean plant, this area will become the stem where it connects to the root. The epicotyl is the area above the cotyledons and below the pumule. It becomes the stem of the growing plant. Leaves eventually grow from the stem.