What Plants Need to Grow
Understand how water, light, and a suitable temperature affect the growth and health of green plants such as beans
What a learner can do afterwards
- Name three conditions to check when growing a bean plant: water, light, and suitable temperature
- Predict how a bean plant may change without light or water, or when exposed to freezing cold
- Describe the results of a simple test comparing plants grown in different conditions
1 · Read
You know that living things have needs. Bean plants need water, light, air, nutrients, and a temperature that suits them. Nutrients help them grow; roots can take mineral nutrients from soil. Here we compare water, light, and temperature. Green plants use light, water, and a gas from the air to make food.
Water helps keep a plant firm. Without water for a long time, a bean plant can droop, wilt, and dry out. Too much water can also harm roots. Freezing cold can damage young bean plants. Different kinds of plants suit different temperatures.
For a fair test, change one condition at a time. Use similar plants in matching pots and soil. To test water, give one group water and leave one without it. Keep light and temperature the same. If water and light both change, you cannot tell which caused a difference. Ask an adult to help with a short test.
Imagine Zara comparing two similar bean plants in matching pots and soil. Both start the same height, get equal water, and stay at the same suitable temperature. Only light differs. Here are made-up results after two weeks: both are 8 cm tall. The plant in light has green leaves. The plant in darkness has pale leaves.
A longer bar shows a greater height. Equal bars show equal heights. Equal height does not mean equal health. Pale leaves can be a sign that a plant is not growing well. Record leaf colour and whether leaves stay firm, as well as height.
Compare water, light, and temperature. Bean plants also need air and nutrients. Change one condition in a test, and record more than height.
This lesson, its made-up example data, questions, worked solutions, and flashcards were written for this dataset.
The five readings and flashcards were written for this dataset. The linked video, The wild world of carnivorous plants - Kenny Coogan, is a TED-Ed lesson by Kenny Coogan. Its publisher terms have not been verified.
More to read
Checking an indoor lettuce plant
A home can be a place to grow lettuce, but being indoors does not give a plant everything it needs.
Check its growing instructions with an adult. Think about the light reaching its leaves. A window may not provide enough.
Check the soil before adding water. Roots can be harmed when soil stays soaked. A pot needs holes that let extra water drain away.
Keep watching the plant as it grows. Its care may need to change.
Bean plants and cold
A young kidney bean plant can be hurt by frost. Frost is ice that forms when surfaces become cold enough. Gardeners wait until the risk of frost has passed before planting kidney beans outside.
Water matters too. Soil that stays soaked can harm the roots.
Beans grown in a garden are not automatically safe to eat. Raw kidney beans can make you sick. Do not eat them. An adult must prepare kidney beans safely before anyone eats them.
A notebook for a plant test
Write down what your plants are like before a test begins. Record their heights and leaf colours. Notice whether their leaves stay firm.
With an adult, compare similar plants for a short time. Change one condition and keep the others alike.
Record the same observations again. Did the heights change? Did the leaves change?
A taller plant is not always a healthier plant. Your notes can show changes that a height measurement misses.
Choosing a place for an eggplant
A young eggplant needs a place warm enough for it. Frost can damage it, so gardeners may keep young plants indoors while outdoor conditions are too cold.
A warm room can still lack enough light. Warmth does not replace light, water, air, or nutrients.
Different kinds of plants suit different conditions. Ask an adult to help read the growing instructions before choosing a place for a plant.
Food and nutrients are different
A green plant makes food using light, water, and carbon dioxide. Carbon dioxide is a gas in the air. Light provides energy for making the food.
Roots take in water and mineral nutrients. Nutrients help the plant grow. Soil is not the plant's food.
A test may compare water, light, or temperature. Those are three conditions we can study, not a complete list of everything the plant needs.
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