See Inside a Seed
Soaked in water, dried beans spring to life. Learn your way around a legume as you explore the various structures that protect and feed a developing plant embryo.
- Set aside a few dry beans for later comparison and place the rest in a cup or bowl.
- Cover the beans with water and let them soak for 12 to 24 hours.
Take the beans out of the water and compare them to the dried beans. Using the hand lens, examine the outsides of the beans. What do you notice?
Gently remove the soft outer coating of a soaked bean. Break the inside of the bean in half lengthwise, and use the hand lens to look closely at the shapes, colors, and structures inside. If you’d like, focus your observations by drawing what you see.
A bean is actually a seed that contains the embryo of a future plant. The embryo is packaged with a food source to use during its early stages of growth, and is covered with a protective seed coat. Soaking the bean in water activates germination of the seed, and the embryo inside begins to grow and unfold.
When you removed the seed coat, you probably noticed a small, white, root-like structure sticking out from one side of the bean. This structure, called the radicle, is the future root of the plant.
When you split the bean open, you may notice tiny white leaves on the end of the radicle. These are the first true leaves of the bean plant.
The bulk of the inside of the bean is the cotyledon, or seed leaf. Each bean contains two cotyledons that separate when you split apart the bean. When the bean sprouts, the cotyledons turn green and have the appearance of leaves (hence their alternate name, seed leaves), but they’re actually not (yet) photosynthetic. Filled with stored starches, fats, and proteins, the cotyledon supplies energy to the developing embryo during the early stages of its growth. Later, once the embryo has used the food stored in the cotyledon, the plant will begin to make its own food through photosynthesis, which occurs in both the seed leaves and the true leaves.
To continue watching your bean plants develop, put a few soaked beans on a wet paper towel in a covered container or sealed plastic bag. Compare the structures that emerge to those you saw in the bean embryo. What emerges first from the sprouting bean? Can you tell the difference between the cotyledon and the true leaves?
Try examining the insides of other seeds, especially those you might find in your kitchen. Rice, corn, wheat, peas, peanuts, and almonds are all seeds. Do they look similar to beans?
You’ll find that corn, rice, and wheat don’t easily split into two halves, as the bean did, and the embryo may be smaller. These plants, called monocots, have one small cotyledon, and store the majority of their embryo’s food in a structure called the endosperm. Like the beans you examined here, peas, almonds, and peanuts are all dicots.
This Science Snack is part of a collection that highlights Black artists, scientists, inventors, and thinkers whose work aids or expands our understanding of the phenomena explored in the Snack.
Source: Tuskegee University Archives/Museum
George Washington Carver (1864–1943), pictured above, was an agricultural scientist, inventor, and professor. Carver applied his knowledge of soil chemistry to help save the cotton farms that were failing in the South. He realized that years of growing cotton had depleted the soil, and by growing nitrogen-fixing plants like peanuts, soybeans, and sweet potatoes, the soil could be restored. Not only did crop rotation produce more cotton, but also a bonus of surplus peanuts. Carver developed over 300 uses for peanuts. Born a slave who became a professor, he was remembered for his peanuts after testifying before Congress on behalf of the peanut industry. Carver was the first African American to earn a Bachelor of Science degree. In this Science Snack, you can explore the parts of a seed and learn what helps it grow.