Parts of a Soy Bean Plant

Root System

• After the soybean seed is planted, it develops a primary root system in order to anchor the plant. This primary root remains for about five to 15 days. During this time, the primary root spreads out. Once the plant develops further, the root system becomes a taproot system. These roots can grow around 5 feet deep, though the roots usually only reach down a foot. The taproots deliver nitrogen from the soil to the plant's stem.

Stem

• Soybean plants emerge from the soil with a hypocotyl hook, which is the curved growth that emerges from the seed and later becomes the stem. This part develops below the cotyledons (seed leaves). It lengthens, straightens and grows quickly in a period known as the vegetative period. The stem features a tip known as the terminal bud, the removal of which may cause side branches to grow on the plant. The stem develops nodes, which are areas at which the leaves attach to the stems. Once the soybean plant matures, the stem turns yellow or brown.

Leaves

• Just after emerging from the soil, soybean plants develop seed leaves known as cotyledons. Cotyledons come from the original germinated seed and provide the young plant with food as it grows. These seed leaves remain on the plant until the first set of real leaves develop. After the photosynthetic leaves develop, the cotyledons fall off. From there, the real leaves produce food for the plant using photosynthesis. The unifoliolates develop first, growing with one leaf on a petiole, the small stalk attaching the leaf to the stem. Following that, the leaves grow in leaflets of three and are known as trifoliolates.

Flower

• After development of six to 10 trifoliate leaves, soybean plants enter their reproductive period. During this time, they develop flowers. These flowers grow on the nodes of the plant, with each node supporting between three and 15 flower buds. The blooms resemble pea or clover flowers. They grow to about ¼-inch wide and come in white, pink or purple. The flowers feature both male and female parts. Soybean flowers engage in self-pollination in order to produce seeds.

Pod

• Once a soybean plant flowers and is pollinated, the plant produces a pod, usually about one to two weeks after flowering. Soybean seeds grow inside the pods, with each pod usually containing three to four seeds. Food from the leaves carries to the seeds in order to fill them. The University of Illinois National Soybean Research Laboratory notes that upon first developing, soybean seeds contain approximately 90 percent moisture. During the filling period, this number decreases to between 45 to 55 percent. Pods turn from green to yellow or brown once the seeds mature, while the mature soybean seed turns yellow.