How Plants Grow
FoundationA seed needs water, air and warmth to sprout, and sunlight to grow; plant a bean yourself and watch it all happen.
- Seeds need water, air and warmth to sprout.
- The root grows first, then the stem and leaves.
- Sunlight helps leaves make food.
文體小知識：說明文一邊講種子的生長過程，一邊教你做一個種豆小實驗，一邊讀一邊種。
§Text Passage
1How does a tiny seed become a tall plant? Give it the right conditions and a miracle happens. A seed needs three things to sprout: water, air and warmth. Missing any one, the seed keeps sleeping.
2The seed drinks water until its skin bursts, and a little white root grows downwards — this is sprouting. Then a tender stem pushes up out of the soil and opens two small leaves. The roots take in water, the stem carries it, and the leaves use sunlight to make food.
3Growing plants also need sunlight. Try a comparison: put one pot of bean seedlings by the window in the sun and another inside a cupboard. After a week, the window seedlings are green and tall; the cupboard ones are yellow and weak. This proves plants need sunlight to grow.
4Try it yourself: take a clear plastic cup, line it with wet cotton, add two mung beans, water it a little each day, and record the changes. It sprouts in about three to five days and grows leaves in two or three weeks. Draw it every day and you will have a plant growth diary.
1Summary 重點摘要
A seed needs water, air and warmth to sprout, and sunlight to grow; plant a bean yourself and watch it all happen.
2Vocabulary cards Vocabulary
The tiny start of a plant; it sprouts in the right conditions.
When a seed takes in water and grows a root and shoot.
The part of a plant under the soil that takes in water.
The part that grows upwards and carries water to the leaves.
The green part of a plant that uses sunlight to make food.
The earth plants grow in, which holds nutrients.
Light from the sun that plants use to make food.
To give plants water — a little and not too much.
3Step by step Steps
- Step 1: Remember the three sprouting needsA seed needs three things to sprout: water, air and warmth, and none can be missing. Put three beans on dry cotton, on wet cotton, and in the fridge — only the one on warm, wet cotton sprouts, because it has all three; the fridge is too cold, and dry cotton has no water, so the other two cannot sprout. Before growing beans or flowers, check that the three conditions are all met, and the chance of success is much greater.
- Step 2: Watch the root and stemWhen a seed sprouts, the root grows down and the stem grows up, each doing an important job. Plant a bean in a clear cup; through the wall of the cup you can see the white root stretch downward and the young stem push up out of the soil, as if greeting us. The root takes in water and grips the soil; the stem carries water and nutrients up to the leaves and holds the whole plant up. They are the plant's helpful workers, each with its own duty, and neither can be spared.
- Step 3: Notice leaves seeking lightA plant's leaves need sunlight to make food, so they follow the light as they grow. Turn the pot on the windowsill around, with the leaves facing away from the window; in a few days the leaves slowly lean towards the window again, waving at the sun. This simple experiment shows that plants are living things and respond to light; keep a pot where the light is good, and the leaves grow green and the plant sturdy.
- Step 4: Water just rightToo much or too little water both stop a plant growing well; the right amount matters most. Two or three spoonfuls a day is usually enough; with too much water the roots stay soaked in wet soil, rot, the leaves yellow, and the plant wilts. Feel the soil with a finger before watering and water only when the surface is dry; pour slowly on the soil and let the water seep down, never straight onto the young shoots and leaves, so the roots can breathe well and grow healthy.
- Step 5: Compare sun and shadeSunlight is the source of a plant's food; without it, plants grow thin and yellow. Put two pots of bean seedlings sown at the same time — one by the window, one in the cupboard — keep the watering the same in amount and time, and after a week compare who is taller and greener. The window pot grows green and sturdy with a thick stem; the cupboard pot turns yellow and weak. The comparison proves plants need sunlight to grow; keep every other condition the same, and the conclusion is reliable.
- Step 6: Keep a growth diaryPlants change quietly every day, and a growth diary keeps those changes one by one. Draw the seed on day one, the white root on day three, the shoot on day five; then measure the height every two or three days, writing down the numbers and dates, and photos can be added too. As the diary fills page by page, it is like watching the plant grow up with you, and it trains careful observation and truthful recording — the basic skills of every scientist.
4Diagrams Diagrams
5Worked example Example
Example: May planted a bean on dry cotton inside a cupboard, and after two weeks nothing sprouted. Give the reason and the fix.
- Check the water first: the cotton was dry and the seed could take in no water — the main reason it did not sprout.
- Check the temperature next: the cupboard was warm enough, so temperature was not the cause.
- Conclusion: sprouting needs water, air and warmth together, and May's seed was missing the water.
- The fix: move the seed onto wet cotton, add a little water each day, keep it in a warm spot by the window, and it will sprout within days.
- Answer: It lacked water. Seeds need water, air and warmth to sprout; on wet cotton, watered daily and kept warm, the seed meets all three conditions and will sprout within a few days.
6Common mistakes Mistakes
7Quick check Quick check
Q1What three things does a seed need to sprout?
Q2Which grows first, the root or the leaf?
Q3What do leaves grow towards?
Q4What happens if we water too much?
Q5What happens to bean seedlings kept in a cupboard for a week?
8Recap Recap
- Seeds need water, air and warmth to sprout.
- The root grows first, then the stem and leaves.
- Sunlight helps leaves make food.
- Water suitably — too much rots the roots.
- Keep a growth diary to record each day's changes.