Rocket waters his bean every day. "So where does all that water go?" he wonders. "The cup never overflows."
Raven looks at a leaf. "What do you notice on the bottom side?"
Nova zooms in close. "Leaves have very tiny doors," she says. "What could slip out through a door?"
Rocket gasps. "Water!"
Leaves have tiny openings called stomata.
In most plants, most stomata are on the underside of the leaf.
Each opening has two guard cells around it.
Guard cells open and close the opening, like doors.
Stomata let water vapor out. They let air gases in and out too.
Water vapor is water as a gas. You cannot see it.
When a plant lets water vapor out of its leaves, it is called transpiration.
As water leaves, it pulls more water up the stem behind it.
Plants lose most of the water they take up.
They use only about two percent of it to grow and make food.
When the soil is dry, a plant can close its stomata.
That saves water.
Stomata also close in the dark.
| Statement | True or false? |
|---|---|
| Stomata are tiny openings on leaves. | ? |
| A plant uses almost all the water it takes up to grow. | ? |
| Stomata close in the dark. | ? |
| Water leaving the leaves helps pull more water up. | ? |
Wonderful thinking! Tomorrow we find out how weather changes how fast leaves let water go.