NCERT Solutions for Class 9th Science Chapter 12 Let us compare — Activity 12.7
Book page 238 Updated on2026-09-08
Q1.
Recall the cross section of the sunflower stem you have studied in Chapter 3 (Fig. 3.7).
Answer
The sunflower is a dicot angiosperm — the most advanced plant group in this chapter. Its stem cross section, from Chapter 3, is arranged as follows:
An outer epidermis with a cuticle.
A zone of cortex below it.
The vascular bundles arranged in a ring, evenly spaced, each bundle with xylem towards the inside and phloem towards the outside.
Between the xylem and phloem of each bundle, a strip of cambium — a layer of dividing cells.
A large central pith.
Tip: the two things worth fixing in your mind are the ring arrangement and the presence of cambium. Both are about to become the point of the comparison.
Q2.
Compare the cross section of the stem of a fern, a pteridophytic plant (Fig. 12.11) with a cross section of sunflower stem you studied in Chapter 3 (Fig. 3.7).
Answer
Feature
Fern stem (Pteridophyta, Fig. 12.11b)
Sunflower stem (Angiosperm, Fig. 3.7)
Xylem and phloem
Present
Present
Arrangement of vascular tissue
Scattered bundles / a central core, not in a neat ring
Bundles in a regular ring around a central pith
Cambium
Absent
Present, between xylem and phloem
Growth in thickness
Very limited — no new vascular tissue can be added
Possible — the cambium keeps making new xylem and phloem
Vessels in the xylem
Mostly tracheids only
Vessels present — wider, faster water conduction
Pith
Small or not clearly marked off
Large and well defined
The same tissue, differently organised: a fern's bundles are scattered and fixed in number; a sunflower's lie in a ring and can add more through cambium.
Q3.
What difference do you observe in the vascular tissue of the fern stem and of the stem of higher plants? Write your observations. Share and discuss them in class.
Answer
Both have xylem and phloem — the difference is in how the tissue is organised and whether it can go on being made.
Observations to write down:
The fern's vascular tissue is simpler and less organised: bundles scattered through the ground tissue rather than a regular ring around a pith.
The fern's xylem consists mainly of tracheids, which are narrow; higher plants also have wide vessels, so water moves faster and in greater volume.
The fern has no cambium. The higher plant has cambium between the xylem and phloem of every bundle.
Why the cambium is the important difference: without cambium, a fern is born with all the vascular tissue it will ever have. As the plant grows, the same fixed set of pipes has to supply an ever-larger body — so the fern quickly hits a ceiling on how tall and thick it can get. With cambium, a sunflower or a tree keeps adding new xylem inward and new phloem outward every season. The pipe system grows with the plant. That is why the largest living things on land are seed plants and not ferns, and it is the anatomical reason wood exists at all.
Talking point for the class: the fern has solved transport but not growth in girth, and it has not solved reproduction on land either — it still needs water for fertilisation and makes no seeds. Each plant group in this chapter solves the previous group's problem and leaves one of its own.