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NCERT Solutions Curiosity Chapter 10 .1 How Do Plants Grow? — Activity 10.1: Let us test some explanations

Book page 138 & 13910 Updated on2026-09-05

Q1.
Observe the plants for two weeks and record changes in their height, number of leaves, colour of leaves, and any other changes that may appear. Record your observations in Table 10.1.
Answer

Three identical pots of garden soil, each with a similar chilli or tomato sapling, are kept as shown in Fig. 10.1 — A in direct sunlight with water, B in direct sunlight without water, C in the dark with water. Here is Table 10.1 with the readings a class usually gets after two weeks.

Table 10.1: Effect of sunlight and water on plant growth
Pots kept under different conditionsAvailability ofHeight of plant (cm)Number of leavesColour of leaves (Green/Yellow)
SunlightWaterDay 1After 2 weeksDay 1After 2 weeks
Pot A: In direct sunlight, with waterYesYes1017613Green (healthy, upright)
Pot B: In direct sunlight, without waterYesNo1010 (drooped, then dried)62 (rest fell off)Yellow to brown, dry
Pot C: In the dark, with waterNoYes1013 (thin, weak, leaning)68 (small)Pale yellow-green

Other changes worth recording: the stem of Pot A becomes thicker and sturdy; the plant in Pot C becomes thin and spindly and bends towards any crack of light; the soil in Pot B becomes hard and cracked.

Check it yourself: write down the height and leaf count on Day 1 before you separate the pots. Numbers taken only at the end cannot show growth.
Q2.
What differences did you observe between the plants in the three pots?
Answer

The three plants started alike but ended up completely different.

  • Pot A (sunlight + water): tallest, most leaves, dark green leaves, thick upright stem — a healthy plant.
  • Pot B (sunlight, no water): the leaves first drooped, then turned yellow and dry and fell off. There was almost no increase in height. The plant wilted and may have died.
  • Pot C (dark + water): the plant stayed alive and even grew a little taller, but it was thin, weak and pale yellow-green, with small leaves. It leaned towards any light that entered.
Why Pot C turns pale: in the dark, the leaves cannot make food and do not develop their full green colour, because chlorophyll needs light. The plant lives for a while on the food already stored in it — that is why it can stretch upward but cannot become strong.
Q3.
Which pot has the plant with the maximum growth?
Answer

Pot A — the pot kept in direct sunlight with an adequate amount of water every day.

It is the only pot in which both the things being tested are available at the same time. The plant gets sunlight to make food and water both as a raw material and to stay firm, so it grows tallest, produces the most leaves and keeps them dark green.

Q4.
Which pot has the plant with the least growth?
Answer

Pot B — the pot kept in direct sunlight without any water.

Water is needed to keep the plant firm, to carry minerals up from the roots and as a raw material for food-making. Without it the plant wilts, its leaves dry and fall, and it may die — so its growth is the least, even though it received plenty of sunlight.

Tip: do not confuse "least growth" with "looks weakest in colour". Pot C looks pale but still gains height; Pot B gains almost nothing at all.
Q5.
What do you infer from the observations made in this activity?
Answer

Plants require both sunlight and water for their growth.

Sunlight + water (Pot A) → best growth
Water but no sunlight (Pot C) → poor, pale, weak growth
Sunlight but no water (Pot B) → wilting and death

Removing either one damages the plant, so neither can replace the other. This is why the experiment uses three pots: pot A is the comparison (control), and pots B and C each remove one factor.

Why the pots must be identical otherwise: same size pots, same garden soil, saplings of the same kind and similar size. If the pots differed in more than one way, we could not say which change caused the difference in growth.
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