Lesson 1
Tall cells in a tidy row
If you sliced a leaf and looked with a microscope, you would see a row of tall, column-shaped cells just under the top skin of the leaf. Scientists call them palisade cells, because they stand side by side like the posts of a fence.
They are a kind of plant cell, and they are packed with little green parts called chloroplasts. Chloroplasts are what make leaves look green.
Below them are rounder, looser cells with lots of air spaces in between.
Try thisPick a leaf and look at both sides. On many leaves the top is a darker green. That is where the tall food-making cells are packed in!
Lesson 2
Cooking with sunlight
Making food from light is called photosynthesis. The chloroplasts do it using three things:
- Sunlight shining down on the leaf.
- Water that travels up from the roots.
- Carbon dioxide, a gas from the air.
Out comes sugar, which is the plant's food, and oxygen, which goes back into the air.
Try thisScroll up to the 3D model and press Shine the sun to light up the chloroplasts.
Lesson 3
How air gets in
The air comes in through tiny doors on the leaf called stomata. Special guard cells open and close them. The air drifts through the air spaces up to the tall food-making cells.
Try thisPress Air comes in on the 3D model to watch air float in through a stoma.
Wow!The oxygen you breathe was made by plants and other tiny living things that make food from sunlight. Thank a leaf!