The Various Parts of the Bean Seed Plant & Their Functions

Roots

• Beans fibrous roots that spread out to gather water and nutrients One, the taproot, is larger than the others and branches into many finer roots. Although plants manufacture their own food in the leaves using energy from the sun, they need the minerals absorbed by the roots as building blocks for growth. Beans, like other legumes, have nodules on their roots that house bacteria that turn atmospheric nitrogen into compounds that the plants can use directly, freeing them from dependence on nitrogen in the soil.

Stem

• The bean stem is long and thin, adapted for twining through other plants or similar supports. The leaves are attached at places called nodes and the spaces between them are called internodes. The stem serves to lift the leaves high enough to gather sunlight for photosynthesis, above competing plants. It also transports nutrients from the roots to the leaves and carbohydrates and proteins from the leaves to the rest of the plant. The tip of the bean vine grows quickly, twisting around completely several times a day until it encounters a solid object. Changes in the production of hormones then cause the stem to twine around the object as it grows.

Leaves

• Leaves are where the red and blue wavelengths of light are absorbed by the chlorophyll pigment. The energy is used by tiny structures in the cells called chloroplasts to form organic compounds such as carbohydrates, food for the whole plant. Green wavelengths are not used and are reflected outward, giving leaves their green color.

Flowers

• Bean flowers, like those of other legumes, are asymmetrical, having one large upper petal, called the banner, and two smaller side petals, the wings, which surround the bottom petals that are fused to form the keel. The stamens, the male organs, and the pistil, the female organ, are enclosed within the keel and the ovary containing the embryos lies at the base of the petals. After fertilization, the ovary swells to become the pod that contains the developing seeds. As the seeds ripen, the pod dries and eventually splits, allowing the bean seeds to fall to the ground.