How Do Plants Grow?
Class 7 Science · Chapter 10: Life Processes in Plants · NCERT Curiosity section 10.1
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Kabir's grandmother's tomato plant has grown new leaves and branches, and its stem has thickened. "We never feed it," says Kabir. "Maybe it eats soil," guesses Neel. "I think water helps," says Zoya. "And sunlight!" adds Meher. They decide to test their ideas.
They plant three similar chilli saplings: Pot A in sunlight with water, Pot B in sunlight without water, Pot C in the dark with water. After two weeks, A is tall and green, C is thin and pale yellow, and B has wilted. Plants need both sunlight and water to grow. An old Indian text on plant care, the Vrikshayurveda, also noted that trees don't fruit just because they are planted: they need care, good soil and manure.
Explore: what do plants need?
- Check each pot and sort it.
Remember
- Plants grow by adding leaves, branches, height and stem thickness.
- A fair test with three pots shows plants need both sunlight and water.
Quick check
A plant kept in the dark but watered daily grows …
- thin and pale yellow
- tall and dark green
- faster than in sunlight
- exactly the same
Answer
thin and pale yellow. Without sunlight it cannot make enough food.
Think about it
Why must the three pots have the same soil and similar saplings?
One answer
So that only one thing (light or water) differs; then any difference in growth can be blamed on that one thing.
Practice
Practise with fresh questions at three levels (easy, medium, hard), some answered hands-on, with hints and worked answers. Get 4 of your last 5 right to finish the topic.