Experiment: Those Swell Seeds

On January 9, 1948, a 220-foot (67 m) steel schooner named the Cali left Guayaquil, Ecuador, loaded with grain, bound for Santiago, Cuba. On January 27, the Cali began taking on water during a storm near Grand Cayman Island. As the seawater leaked in, the grain swelled up so much that it ruptured the hull and destroyed the ship!

To the casual observer, seeds appear lifeless and simple. However, under the right conditions, they will germinate (start growing). But this process depends heavily on the presence of water. God designed seeds with the amazing ability to soak up and hold the water necessary for the complex processes of life.

Most seeds, such as grains, beans, corn, and nuts, undergo a resting phase before they begin growing into new plants. During this phase, most seeds contain very little moisture. The seed coat, or outer skin, keeps water out. The chemical processes that keep the cells functioning in the seed are slowed almost to a halt. Seeds can remain in this resting state for months, years, or even centuries. The delay allows seeds to survive harsh, unsuitable environmental conditions. It also allows time for transportation by wind, water, animals, or people.

When conditions become favorable, the seed coat goes through a marvelous transformation that allows water to soak the seed. The process of seeds absorbing water is called imbibition.

During imbibition, a seed can swell to several times its original size. This swelling can cause tremendous pressure—often over 1,000 pounds per square inch (6900 kPa). Swelling seeds can break rocks and concrete or, in the case of the Cali, rupture a steel cargo ship. This swelling bursts the seed coat, allowing the new plant to grow and lodging the plant in place so it can’t wash away or be blown away by wind. The expanding plant can then take root in even the hardest soils.

What causes imbibition in seeds? Certain molecules in seeds, such as starches and cellulose, develop tiny electrical charges when wet. God uniquely designed water to bond easily with these molecules. Like tiny magnets, these substances then pull more and more water into the seed, causing the seed to swell up like a water balloon. The added water activates the seed’s growth hormones, causing germination. Whenever you cook oatmeal, rice, or beans, you observe imbibition.

Seeds don’t hold a monopoly on imbibition. It also occurs in other plant and animal products, such as wood and sponges. In an ancient stone-cutting technique, people would drive dry wooden pegs into holes drilled into rock. When the wood pegs were soaked with water, the pegs swelled, splitting the rock. Some archaeologists believe that the Egyptians cut stone blocks in this way to build the pyramids.

So the next time you notice a blade of grass peeking through a crack in the sidewalk, or as you cook your next pot of scrumptious beans or rice, remember to praise the Creator for His wisdom. He gave even little seeds unique designs that allow them to expand to the ends of the earth, glorifying their Maker as they provide food and other necessities for living things (Genesis 1:29–30).

See For Yourself . . .

Are expanding seeds really strong enough to break apart rocks? Try this experiment to find out!

Materials

6 tablespoons (90 ml) plaster of Paris, 2 small cups, 4 dried lima beans, pen or marker, masking tape or labels, 2 paper towels, water

Procedure

1. Mix the plaster of Paris and water according to the directions on the package. Pour half the prepared plaster into each cup.
2. In the first cup, push the 4 beans into the plaster so that about three-fourths of each bean is below the surface of the plaster. Label this cup TEST. Label the cup without beans CONTROL. Record a description of how the surface of the plaster in each cup appears. Is it smooth? Are there any cracks or bulges?
3. Fold each paper towel in half twice. Wet the folded towels with water so that they are moist but not dripping wet. Place the moist paper towels on top of the plaster in each cup so that they lie flat on the surface. In 1 hour, examine the two cups. Do you see any changes? Repeat this step every hour for 12 hours or until no further changes are observed.