A dry bean has a tough coat. It is built from a tight row of tall, rod-shaped cells called macrosclereids, standing side by side like a fence!
Drag to turn it around. Use the buttons to zoom in and try things from the lessons.
The 3D model can't load right now. Check your internet connection, or try a different web browser.
Macrosclereids are long, rod-shaped cells with very thick, hard walls. They stand up straight, packed tightly side by side, like the posts of a fence.
They make the outer layer of the seed coat in many seeds of the bean family, such as beans, peas, and lentils.
Like other sclereids, they are dead when grown, and their walls are so thick that there is only a thin space left inside.
Press Cut it open on the 3D model to see how thick the walls are.
The seed coat protects the baby plant inside the seed. The tight fence of rod cells helps keep out bugs and germs, and slows down water getting in.
That way, many seeds can wait, safe and dry, until the time is right to sprout.
Put a few dry beans in a cup of water overnight. In the morning, they are bigger, and the coat may be wrinkly or peeling. Water finally got through the tough coat!
Some seeds with very hard coats can wait for years before they sprout.
By SciShow Kids. A fun video for kids.
Watch on YouTube →