Seed Structure of a Common Bean

History

• Beans are native to the Americas and were first domesticated in Central and South America over 7,000 years ago. The common bean is one species, Phaseolus vulgaris L. The beans we are used to seeing on our dinner plates, such as kidney, navy and pinto beans, are all varieties of the common bean. Beans are now second only to tomatoes in garden planting popularity.

Plant Types

• There are many types of common beans, however; the structure of the seed remains consistent amongst the types of beans. Two varieties of bean plants are the bush beans, which do not require support to stand, and pole beans, which require climb supports. Green beans are available in both a bush and pole variety. Yellow beans only grow in a bush variety.

Function

• Bean seeds are found in the pods of the bean plants. The bean seed itself has parts with specific functions. The cotyledon feeds the sprouting bean plant, the plumule develops into the mature bean plant and the radicle becomes the primary root for the bean plant. Secondary roots develop from the radicle as it grows downward. The outer shell of the bean plant or the seed coat holds and protects the plant inside.

Features

• Bean seeds are dicots or dicotyledon, meaning they have two cotyledons that feed the bean sprout. The future stem grows in between the two cotyledons. The cotyledons take up most of the volume of the bean seed. The hilum marks where the seed was attached to the pod with a string-like placenta. It is identified as a scar on the in-curving edge of the bean. The plumule can be seen on one side of a bean that has been halved. It looks like a little worm and sometimes minuscule veins on the plumule can be seen as well. The radicle can be seen right below the plumule and the hypocotyl is the space between the radicle and the cotyledons. The seed is covered by the seed coat, which develops from skin that once covered the ovule inside the flower's ovary and can range in color through the whole color spectrum.

Benefits

• Beans are considered easy to grow. They prefer warm weather, full sun and well-drained soil. They require shallow cultivation due to weak root systems. Additionally, beans are sensitive to weather extremes.