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NCERT Solutions for Class 7th Science Chapter 10 .3.1 Transport of water and minerals — Activity 10.7: Let us experiment

Book page 14810 Updated on2026-09-19

Q1.
What do you notice? Compare the plant stems placed in the tumblers. Do you observe red colour in the stem, leaves, and flowers of the plant from Tumbler B?
Answer

Yes. After one day, the twig standing in Tumbler B (water + a few drops of red ink) shows a clear red tinge — fine red streaks run up the stem, red lines appear along the veins of the leaves, and the white flowers turn pink or red (Fig. 10.7d).

The twig in Tumbler A, standing in plain water, looks exactly as it did before (Fig. 10.7c) — the stem is green, the flowers still white.

TumblerContentsAppearance of the twig after one day
AWater onlyNo change — stem green, leaves green, flowers white
BWater + a few drops of red inkRed colour visible in the stem, in the leaf veins and in the flowers
Why Tumbler A is needed: A is the control. It proves the red colour came from the ink travelling up the plant and not from the twig drying or ageing.
Q2.
How did different parts of the plant acquire this red colour?
Answer

The twig absorbed the red-coloured water through its cut end and carried it upward inside itself.

The coloured water travelled through the thin tubes of the xylem, which run from the base of the stem into the branches, the leaf veins and the flowers. Wherever the water reached, the dye it carried was left behind and made that part look red.

Tip: the stems are cut obliquely (at a slant) and while kept inside the water. A slanting cut gives a larger surface for absorption, and cutting under water stops air from entering the xylem tubes and blocking them.
Q3.
Cut the stem from the upper part of the plant that is not immersed in the red-coloured water. Observe the cut stem using a magnifying glass. Do you spot the red colour in the stem (Fig. 10.7e)?
Cut end of the twig seen enlargedCutPhloemXylem(e) Enlarged view of cut end of the twig
Fig. 10.7(e), page 148 — enlarged view of the cut end of the twig.
Answer

Yes. In the freshly cut cross-section, the red colour is not spread all over. It appears as a ring of small red dots or dashes arranged in a circle inside the stem (Fig. 10.7e).

Each red dot is the cut end of one xylem tube filled with the coloured water. Just outside them lies another set of tubes, the phloem, which stays uncoloured because it does not carry this water.

Why this observation is important: it shows the water did not soak through the whole stem. It travelled along a definite set of pipes — which is exactly what a transport system means.
Q4.
How does the red colour ink move upwards?
Answer

Through the xylem — thin tube-like structures present in the stem, branches and leaves of plants. Just like red ink, minerals dissolved in water also move up the stem through the xylem.

Transport of water through xylem and food through phloem soil level Water transport through xylem Food transport through phloem Leaves — food is made here Roots — water and minerals are absorbed here
Two separate sets of tubes run through the plant: xylem carries water and minerals upward from the roots, phloem carries food away from the leaves in all directions.
Try This: split the lower half of a white gladiolus or sadabahar stem lengthwise and dip one half in red ink and the other in blue ink. After a day the flower is half red and half blue — proof that separate xylem tubes carry water along separate paths.
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