Plants and Photosynthesis
Grade 3 · Science · Study Guide
Discover how plants make their own food using sunlight, water, and air.
Plants are amazing living things because they can make their own food. This process is called photosynthesis, and it happens inside the green parts of a plant, mainly the leaves.
Here's how it works: plants take in water through their roots. The water travels up through tiny tubes in the stem called the xylem. At the same time, the leaves have tiny holes called stomata that let in a gas from the air called carbon dioxide. Inside the leaf cells are green structures called chloroplasts, which contain a green pigment called chlorophyll. Chlorophyll captures energy from sunlight.
With sunlight energy, water, and carbon dioxide, the plant makes glucose — a type of sugar it uses for energy and growth. As a bonus, oxygen is released through the stomata, which is the very air we breathe! The simple formula is: water + carbon dioxide + sunlight → glucose + oxygen.
Plants need the right conditions to make food well. Too little light and they can't photosynthesize enough. Too little water and they wilt. Understanding photosynthesis helps us understand why plants are so important — they are the base of almost every food chain on Earth.
| Plants Take In | Plants Give Out |
|---|---|
| Water (from roots) | Oxygen (through stomata) |
| Carbon dioxide (through stomata) | Glucose (stored as food) |
| Sunlight (absorbed by chlorophyll) | Water vapor (through stomata) |
Key terms
- photosynthesis
- The process plants use to make food using sunlight, water, and carbon dioxide
- chlorophyll
- The green pigment in plants that captures sunlight energy
- chloroplast
- The part of a plant cell where photosynthesis takes place
- stomata
- Tiny pores on leaves that let carbon dioxide in and oxygen out
- glucose
- The sugar that plants produce during photosynthesis to use as food
Flashcards
- photosynthesis
- How plants make food using sunlight, water, and carbon dioxide
- chlorophyll
- Green pigment that captures energy from sunlight
- stomata
- Tiny openings in leaves for gas exchange
- glucose
- Sugar made by plants during photosynthesis
- carbon dioxide
- A gas plants absorb from the air to use in photosynthesis
- oxygen
- Gas released by plants as a byproduct of photosynthesis
Practice questions
What gas do plants absorb from the air to make food?
- Oxygen
- Nitrogen
- Carbon dioxide
- Hydrogen
Show answer
Answer: Carbon dioxide
Plants take in carbon dioxide through tiny holes in their leaves called stomata. They combine it with water and sunlight to make glucose.
Plants make their food in their roots.
Show answer
Answer: False
Photosynthesis happens mainly in the leaves, where chloroplasts and chlorophyll are found. Roots absorb water but don't make food.
The green pigment in plants that captures sunlight is called ___.
Show answer
Answer: chlorophyll
Chlorophyll is the green pigment found inside chloroplasts. It captures light energy needed to power the photosynthesis reaction.
What is the sugar that plants produce during photosynthesis called?
- Fructose
- Glucose
- Starch
- Cellulose
Show answer
Answer: Glucose
Plants produce glucose during photosynthesis. They use glucose for energy and growth, and can convert it to starch for storage.
Plants release oxygen as a product of photosynthesis.
Show answer
Answer: True
Oxygen is released through the stomata as a byproduct of splitting water molecules during photosynthesis — it's how plants contribute oxygen to Earth's atmosphere.
Fun facts
- A single large tree can produce enough oxygen for four people to breathe for a whole year!
- Leaves look green because chlorophyll reflects green light back to our eyes while absorbing red and blue light.
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