NCERT Solutions for Class 9th Science Chapter 3 End-of-chapter questions — Revise, Reflect, Refine

Book page 44 Updated on2026-09-08

Q1.

Meristematic tissues divide repeatedly. What property of their cells allows them to do this? (i) They have thick walls for protection. (ii) They contain large vacuoles that store nutrients. (iii) They have thin walls, dense cytoplasm and large prominent nucleus. (iv) They are functionally differentiated cells.

Answer

(iii) They have thin walls, dense cytoplasm and large prominent nucleus.

Why this is the right set: each feature is directly useful for division —

Thin walls — the wall can be stretched and a new wall laid down quickly between the daughter cells. A thick lignified wall would make that impossible.
Dense cytoplasm with many organelles — ribosomes to make protein, mitochondria to supply the energy, ER and Golgi to build new membranes and wall material.
Large prominent nucleus — the DNA has to be copied before every division, and a large nucleus in a small cell can control the cell efficiently.
Add to these: vacuoles absent and the cells tightly packed with little or no intercellular space.

Why the others are wrong: (i) thick walls belong to sclerenchyma, which is dead and cannot divide. (ii) large vacuoles are a feature of mature parenchyma; they would push the cytoplasm aside. (iv) a cell that has already differentiated has lost the power to divide — that is what differentiation means.

Q2.

If a plant is unable to transport food from leaves to roots which tissue is malfunctioning? (i) Xylem (ii) Phloem (iii) Epidermis (iv) Sclerenchyma

Answer

(ii) Phloem.

Food is made in the leaves and has to travel downwards to the roots, which cannot photosynthesise. That job belongs to the sieve tubes of the phloem, helped by companion cells that load and unload the sugars.

Why not the others: xylem carries water and minerals upwards from the root, not food downwards. The epidermis is a protective covering. Sclerenchyma is dead, thick-walled supporting tissue and conducts nothing.

Tip: remember the direction — xylem: root → leaf, water. Phloem: leaf → everywhere, food. Question 8 in this set (the debarked tree) is the same idea seen from the outside.

Q3.

Why are the epithelial tissues that line an animal’s internal organs usually only one or a few cells thick? (i) To store food efficiently. (ii) To provide maximum strength. (iii) To allow quick exchange of materials across them. (iv) To reduce friction.

Answer

(iii) To allow quick exchange of materials across them.

Why thinness matters so much: substances cross an epithelium by diffusion, and the rate of diffusion falls as the distance to be crossed increases. A single layer of thin, flat cells gives the shortest possible path, so oxygen from the air in the lungs reaches the blood almost instantly, and digested food crosses the intestinal lining quickly. Table 3.2 makes the link exactly: the exchange epithelium of blood vessels and lungs is a single layer of thin, flat cells.

Why the others are wrong: storing food is not an epithelial job. Where strength is needed the epithelium is not thin at all — the skin, mouth and oesophagus have many layers of tightly packed cells (Table 3.2), which is precisely why they cannot be used for exchange. Reducing friction is done by secretions such as mucus, not by being thin.

Q4.

You can perform these two jumps (Fig. 3.21): Straight-leg jump — keep knees and ankles stiff. Normal jump — bend knees and ankles naturally. How did your ankle, knee and hip positions differ between the two jumps?

Answer

In the normal jump all three joints bend deeply before take-off and bend again on landing; in the straight-leg jump they stay almost locked, and you jump much lower and land with a jolt.

Joint	Straight-leg jump	Normal jump
Ankle	Held stiff; almost no bending, only a small push from the toes	Bends and then straightens forcefully, pushing the foot down against the ground
Knee	Locked straight; the hinge joint is not used at all	Bends deeply into a crouch, then straightens hard to drive the body up
Hip	Stays upright, trunk nearly vertical	Bends forward as the body lowers, then extends as you rise
Result	Low jump, hard landing, jarring felt in the legs and spine	Higher jump, soft controlled landing

Why bending makes such a difference: a muscle produces force only while it shortens. Crouching first stretches the muscles of the thigh and calf, so each has a longer distance over which to pull and can do more work on the body. Three joints working in sequence — hip, then knee, then ankle — add their pushes together. On landing, the same joints bend to spread the impact over a longer time, and the cartilage at the bone ends absorbs the shock. With the joints locked, the whole impact is passed straight up the bones to the spine in an instant, which is why the landing hurts.

Check it yourself: this is why an athlete is coached to land softly on bent knees, and why the same crouch appears in kabaddi, kho-kho and in the araimandi stance of classical dance.

Q5.

Which type of joint is involved when you bend your knees and ankles? (i) Ball and socket (ii) Hinge (iii) Pivot

Answer

(ii) Hinge.

The knee and the ankle both bend and straighten in one direction only, like a door turning on its hinge. At the knee a small bone, the kneecap, sits in front of the joint and protects it.

Why a hinge and not a ball and socket: the knee and the ankle carry your whole body weight, and every landing sends a large force up through them. A hinge allows movement in a single plane and refuses all other directions, which is exactly what keeps the leg stable under load. A ball and socket joint, like the shoulder, buys freedom of movement at the cost of stability — useful for an arm, dangerous for a leg.

(iii) Pivot is wrong — a pivot joint allows rotation, as when you shake your head to say ‘no’.

Q6.

In each of the following cases (A, B, C and D), choose the correct option as given below: (i) Both (A) and (R) are true, and (R) is the correct explanation of (A). (ii) Both (A) and (R) are true, but (R) is not the correct explanation of (A). (iii) (A) is true, but (R) is false. (iv) (A) is false, but (R) is true. A. Assertion: Epithelium is well-suited for gas exchange in the lungs. Reason: It consists of multiple layers of tall cells that slow down diffusion. B. Assertion: Cardiac muscle can contract continuously without fatigue. Reason: Cardiac muscle cells have a high number of mitochondria and an abundant blood supply. C. Assertion: Tendons connect bone to bone and allow joint movement. Reason: Tendons are made of tough connective tissue that transmits force from muscle to bone. D. Assertion: In a hinge joint, movement occurs primarily in one plane. Reason: The bone ends are shaped to allow sliding in all directions.

Answer

Case	Assertion	Reason	Answer
A	True	False	(iii)
B	True	True and explains A	(i)
C	False	True	(iv)
D	True	False	(iii)

A — (iii). The assertion is right: the lung lining is superb for gas exchange. The reason is the exact opposite of the truth. Table 3.2 says the exchange epithelium is a single layer of thin, flat cells, which makes the diffusion path as short as possible. Multiple layers of tall cells would slow diffusion down, so that arrangement is found where protection is needed — skin, mouth, oesophagus.

B — (i). Cardiac muscle really does work rhythmically for a lifetime without fatigue, and the reason given is exactly why. Fatigue sets in when a muscle uses ATP faster than it can make it. A large number of mitochondria means a high rate of aerobic ATP production; an abundant blood supply keeps delivering the oxygen and glucose that those mitochondria need and removes the wastes. Supply therefore keeps pace with demand and no oxygen debt builds up.

C — (iv). The assertion is false: ligaments connect bone to bone. Tendons connect muscle to bone. The reason, taken on its own, is a correct statement — tendons are tough connective tissue and they transmit the force of a contracting muscle to a bone.

D — (iii). The assertion is true: a hinge joint moves in one plane, as the elbow and knee do. The reason is false; bone ends shaped for sliding in all directions describe a ball and socket joint, not a hinge. In fact it contradicts the assertion.

Tip for assertion–reason questions: judge the assertion and the reason separately first, and only then ask whether the reason explains the assertion. In C the reason is true and the assertion is false — a combination that is easy to miss if you read them together.

Q7.

Plot a graph between the age of a tree (in years) on the x-axis and the diameter of the tree (in cm) along with the number of annual rings formed over time on the y-axis, using the data given in the Table 3.7. (i) Analyse the graph in terms of the diameter of the stem over time and share the interpretation. (ii) What is the relation between the diameter of the teak tree to the annual rings formed? (iii) Which specialised tissue is responsible for the girth of the stem and where is it located?

Answer

Plot age on the x-axis and put both DBH (cm) and the number of annual rings on the same y-axis, since both run from 4 to 40.

Both curves rise with age. The rings line is perfectly straight (one ring a year); the DBH line has a steep patch between 10 and 20 years.

(i) Diameter over time. The diameter increases steadily throughout — the tree never stops thickening. But the rate is not the same every year:

Rate of increase in diameter = (change in DBH) ÷ (change in age)

5 → 10 years: (8 − 4) cm ÷ (10 − 5) years = 4 cm ÷ 5 years = 0.8 cm year⁻¹
10 → 20 years: (24 − 8) cm ÷ 10 years = 16 cm ÷ 10 years = 1.6 cm year⁻¹
20 → 25 years: (28 − 24) cm ÷ 5 years = 0.8 cm year⁻¹
25 → 30 years: (32 − 28) cm ÷ 5 years = 0.8 cm year⁻¹
30 → 40 years: (40 − 32) cm ÷ 10 years = 8 cm ÷ 10 years = 0.8 cm year⁻¹

Average over the whole record = (40 − 4) cm ÷ (40 − 5) years = 36 ÷ 35 ≈ 1.03 cm year⁻¹

Interpretation: the young tree (10 – 20 years) grew in girth twice as fast as at any other stage — 1.6 cm year⁻¹ against 0.8 cm year⁻¹. That decade was clearly a stretch of favourable conditions, and the lateral meristem was most active then. After 20 years the rate settles back to a steady 0.8 cm year⁻¹.

(ii) Diameter and annual rings. Rings and age are related exactly one-to-one — 5 years/5 rings, 20 years/20 rings, 40 years/40 rings — because one ring is formed each year. So diameter increases with the number of rings, but not in strict proportion:

Diameter added per ring = DBH ÷ number of rings
At 5 rings: 4 ÷ 5 = 0.80 cm per ring At 20 rings: 24 ÷ 20 = 1.20 cm per ring
At 25 rings: 28 ÷ 25 = 1.12 cm per ring At 40 rings: 40 ÷ 40 = 1.00 cm per ring

Mean radial width of one ring at 40 years = (40 ÷ 2) cm ÷ 40 rings = 20 ÷ 40 = 0.5 cm = 5 mm

So the relation is: more rings → larger diameter, and the number of rings gives the age. Wide rings mark favourable years and narrow rings unfavourable ones, which is why the diameter-per-ring figure is not constant.

(iii) The tissue. The lateral meristem. It is located as a ring of actively dividing cells inside the stem, running along its circumference. Its cells divide and add new cells both inwards and outwards in a concentric manner, so the stem grows in diameter and lays down one annual ring each year.

Did you know? Because each ring records one year's conditions, scientists read old timber the way you read a diary — the widths tell them about droughts and good rainfall years long before any weather records were kept.

Q8.

In a forest, it was observed that one of the trees was severely debarked by an elephant to meet its food requirements, as the bark is a rich source of nutrients (Fig. 3.22). Based on your learning, answer the following: (i) Which function(s) of the tree is/are hampered by debarking? (ii) Which plant tissue would be affected by further damage to the tree trunk even after debarking? (iii) Which function of the tree would be hampered if the tissues beneath the bark were severely damaged? (iv) What assumptions are you making to answer the questions above? How would the answer change if your assumptions are also changed?

Answer

Work outwards-in. The bark is the outermost protective layer; just beneath it lie the phloem and the lateral meristem; deepest of all is the xylem.

(i) Functions hampered by debarking.

Protection is lost. The bark is made of dead, compactly arranged cork cells containing a substance that makes them impermeable to water and gases. Strip it and the trunk is open to water loss, to fungi, bacteria and insects, and to mechanical injury.
Food transport is interrupted. The phloem lies immediately under the bark, so it is usually torn away with it. Sugars made in the leaves can then no longer reach the roots.
Girth growth stops at that patch, because the lateral meristem sits just inside the phloem and is damaged too.

(ii) Tissue affected by further damage to the trunk. Going deeper, the next tissues to be destroyed are the lateral meristem (cork cambium and the cambium of the vascular bundle) and then the xylem. Xylem damage is the most serious of all, because xylem also gives the trunk its mechanical strength.

(iii) Function hampered if the tissues beneath the bark are severely damaged. The upward transport of water and minerals from the roots to the leaves, since that is the xylem's job — and with it the tree's mechanical strength, so the trunk may snap in a storm. If the phloem is completely ringed all round, the roots are cut off from their food supply, they starve, they stop absorbing water and minerals, and the whole tree eventually dies even though its leaves are untouched.

(iv) Assumptions, and what changes if they are altered.

Assumption made	If the assumption changes…
The debarking goes all the way round the trunk (ringing)	If only a patch on one side is stripped, phloem on the other side still carries food down and the tree usually survives and heals over the wound
The damage reaches the phloem and cambium, not just the outer dead cork	If only the dead outer cork is scraped off, the tree loses protection but keeps transporting food and can regenerate new cork from the cork cambium
The tree is a dicot with secondary growth and continuous bark	A monocot such as a palm or bamboo has no cork cambium and no ring of phloem beneath a bark, so the same injury has a quite different effect
Xylem is still intact	If the xylem is also cut through, the leaves stop receiving water and wilt within days — much faster than death by starvation of the roots
The injury is not re-infected and the season is favourable	If fungi enter the exposed wood, decay spreads and even a partly debarked tree may die

Why the direction of transport decides everything: phloem carries food downwards from leaves to roots, so a complete ring of damage starves the roots but not the leaves. Xylem carries water upwards, so damaging it kills the leaves first. Which tissue is cut tells you which end of the tree dies first.

Q9.

Aamrapali observed that a young mango sapling’s stem bends flexibly during monsoon winds and does not break. Which tissue is responsible for this flexibility? Predict and provide your explanation of the impact if the existing tissue was replaced by sclerenchyma.

Answer

Collenchyma is responsible for the flexibility.

Collenchyma consists of living cells whose walls are unevenly thickened at the corners by the deposition of pectin — a chemical the book compares to rubber. The extra material at the corners gives strength, while the thin regions in between let the wall deform. So the stem can bend under the wind and spring back when the gust passes.

If it were replaced by sclerenchyma:

	Collenchyma (present)	Sclerenchyma (hypothetical)
Wall	Thin, thickened at corners with pectin	Uniformly thick, hardened with lignin
Cells	Living, can grow with the stem	Mostly dead, cannot elongate
In wind	Bends and recovers	Rigid, then snaps once the force exceeds its limit
Effect on growth	Grows along with the young stem	A dead, lignified sheath would restrict the elongation of the young stem

Prediction: the sapling would stand very stiffly in still air, but in the first strong monsoon gust the stem would crack or break outright — the way a dry twig snaps while a fresh twig bends. Its height growth would also be held back, because a lignified wall cannot stretch as the stem elongates.

Why young stems use collenchyma and old trunks use sclerenchyma: a young stem is still growing and still slender, so it needs support that flexes and grows with it. An old trunk has finished elongating and has to carry a great weight, so it can afford rigid, dead, lignified tissue. The plant changes its support tissue as its needs change — structure follows function again.

Q10.

Sohan designed an experiment for the regeneration of sugarcane, where he used cuttings to grow sugarcane. He used two types of cuttings, type ‘A’ and type ‘B’ (Fig. 3.23). After a few weeks, type ‘B’ cuttings sprouted and developed into sugarcane plants, whereas the type ‘A’ cuttings did not sprout. (i) Why were the type ‘B’ cuttings able to grow as sugarcane but type ‘A’ could not? (ii) What difference was present in type ‘B’ compared to type ‘A’? (iii) What observation or measurement was made to determine whether this change had an effect? (iv) What parameters should be kept the same for both types of cuttings to ensure a fair comparison?

Answer

Look carefully at Fig. 3.23. Cutting (A) is a smooth length of stem taken from between two nodes — a plain internode. Cutting (B) carries a node: you can see the swollen ring with a bud on it and the beginnings of root growth.

(i) Why B grew and A did not. Sprouting needs cells that can still divide. A node carries a bud (dormant shoot apical meristem) and the intercalary meristem at the base of the internode just above it. Cutting B has these, so it can produce a new shoot and roots. Cutting A is made entirely of permanent tissue — parenchyma, sclerenchyma, xylem and phloem — every cell of which has lost the ability to divide. It can stay alive for a while, but it has no growing point, so it never sprouts.

(ii) The difference. The presence of a node with a bud (and its meristematic tissue) in B; A is an internode with no node and no bud.

(iii) What was observed or measured. Whether or not a shoot appeared, and then how much. In practice you would record:

number of cuttings that sprouted out of the total planted (percentage sprouting);
the number of days taken for the first shoot to appear;
the length of the new shoot in cm, measured at fixed intervals;
the number of roots formed and their length in cm.

Sprouting percentage = (number of cuttings that sprouted ÷ total cuttings planted) × 100
Example: if 18 of 20 type-B cuttings sprouted, sprouting = (18 ÷ 20) × 100 = 90%
If 0 of 20 type-A cuttings sprouted, sprouting = 0%

(iv) Parameters to keep the same so that only the presence of a node differs:

the same variety of sugarcane, from the same parent plant;
the same length and thickness of each cutting, and cuttings of the same age;
the same soil, the same pot size, the same depth and orientation of planting;
the same amount and frequency of watering;
the same temperature, sunlight and humidity — plant them side by side;
the same number of cuttings of each type, so the percentages are comparable, and the same observation dates.

Why a fair test needs all this: the experiment claims that the node caused the sprouting. That claim only holds if the node is the one thing that differs between the two groups. If the type-B cuttings had also been thicker, or better watered, you could not tell which factor did the work. Everything else is kept constant precisely so that one variable is left free to be tested.

Did you know? Sugarcane, potato and sweet potato are all propagated commercially in exactly this way — from stem pieces carrying buds — because it is faster than seed and gives plants identical to the parent.

Q11.

During the discussion in class, Rohan gives a statement that, “A tissue is a group of similar cells performing similar functions”. But Rajiv counter argues that, “this is true in case of simple tissues but little different in case of complex tissues”. Provide your explanation in view of the discussion in class.

Answer

Rajiv is right, and Rohan's statement needs one word changed. A tissue is a group of cells that work together for a common function — they need not all be the same kind of cell.

	Simple permanent tissue	Complex permanent tissue
Cell types	Only one kind of cell	More than one kind of cell
Examples	Parenchyma, collenchyma, sclerenchyma	Xylem, phloem
How the work is shared	Every cell does the same job — all parenchyma cells store food	Different cells do different parts of one job

Take xylem. It has four different cell types and only one purpose — moving water up the plant:

Tracheids and vessels — tubular, thick-walled and dead; they are the pipes.
Xylem fibres — sclerenchymatous; they give mechanical strength.
Xylem parenchyma — the only living component; it stores food.

Take phloem. Again four cell types, one purpose — moving food:

Sieve tubes — long, tubular, joined end to end by perforated walls; the channel itself.
Companion cells — specialised parenchyma cells that regulate the sieve tube and monitor the loading and unloading of sugars.
Phloem parenchyma — stores food, resin, tannins and latex.
Phloem fibres — sclerenchymatous; they support the soft sieve tubes.

A better definition, covering both cases: a tissue is a group of cells that are organised together and work as a unit to carry out a specific function — similar in structure in a simple tissue, of several kinds in a complex tissue.

Why complex tissues had to evolve: conduction is not one job but several — an open channel, strength to keep it from collapsing, storage, and regulation of what enters and leaves. No single cell type can be hollow and dead and alive and regulating at the same time. So the plant assembles several cell types into one tissue. The same idea appears in animals: blood is a connective tissue made of RBCs, WBCs, platelets and plasma, all serving transport and defence.

Q12.

Coconut husk fibres are used for mats which are tough and fibrous. Which tissue has structural features suitable for providing this strength? Explain why living parenchyma couldn’t serve the same purpose.

Answer

Sclerenchyma. Coconut husk fibre is sclerenchyma, and every one of its features is a strength feature.

Feature of sclerenchyma	What it gives the mat
Uniformly thick walls, heavily deposited with lignin	Rigidity and resistance to being pulled apart or crushed
Long, narrow, tapering cells packed end to end	Fibres that can be twisted into strong yarn and woven
Most cells are dead at maturity	No water content to be lost, so the fibre keeps its shape and strength when dry
Lignin is water-resistant	The mat survives washing, damp floors and rain without rotting quickly

Why living parenchyma could not do this:

Parenchyma cells have thin walls — there is almost no material to resist a pull. They tear easily.
They are loosely packed with intercellular spaces, so the tissue is soft and spongy rather than fibrous.
They are living and full of water. Their firmness comes from turgor, not from the wall. Dry them out and they collapse and shrivel — a mat made of parenchyma would go limp the day it was made.
Being alive, they would also need a food and water supply, and would rot and be attacked by microbes as soon as they were cut off from the plant.

The key contrast: parenchyma is strong only while it is alive and full of water; sclerenchyma is strong because its wall is thick and lignified, and it stays strong after the cell dies. For anything that has to last outside the plant — coir rope, jute, a walnut shell, a seed coat — you need the dead, lignified tissue.

Q13.

Vibha claims to her friend Neha that, “Meristematic cells are located only at the root and shoot apices”. What do you think about this statement? What question can Neha ask Vibha to help her understand further if the statement is incorrect?

Answer

The statement is incorrect. Apical meristem is only one of three kinds. Meristematic cells are also present along the circumference of the stem (lateral meristem) and at the nodes and the base of internodes (intercalary meristem).

Three kinds of meristem, three different jobs — length, girth and regrowth.

Questions Neha can ask Vibha — each one points at a fact her claim cannot explain:

“If meristem is only at the apices, then why does the trunk of a tree get thicker every year, and what forms the annual growth rings we count to find its age?”
“When a lawn is mowed, the shoot tips of every blade of grass are cut off. Why does the grass grow back?”
“After a hedge is trimmed, more branches appear and it turns bushy. Where are the new cells for those branches coming from, if the tip has been removed?”
“In our own Activity 3.1, cutting the root tip stopped the root growing longer, but the onion bulb stayed alive and kept working. Which dividing cells were still present elsewhere?”

Any one of these forces the correct conclusion: apical meristem adds length at the tips, lateral meristem adds girth along the stem, and intercalary meristem at the nodes lets grasses and hedges regenerate after being cut.

Tip: a good counter-question does not just say “you are wrong”. It offers an everyday observation that the wrong idea cannot account for, and lets the other person work it out.

Q14.

A plant cell and an animal cell are of the same size. (i) Which cell will have a larger vacuole? Give reasons. (ii) What assumptions are you making to answer the question above?

Answer

(i) The plant cell. A mature plant cell has one large central vacuole that can occupy most of the cell volume, pushing the cytoplasm and the nucleus into a thin layer against the wall. An animal cell has either no vacuole or only a few very small ones.

Reasons:

Turgor and support. A plant cell has a rigid cell wall. Filling the vacuole with water presses the cytoplasm out against that wall and makes the cell firm — this turgor is what keeps a soft herb upright. An animal cell has no wall, so a big water-filled vacuole would simply burst it or distort its shape.
Storage. The plant makes its own food and stores water, food, pigments and wastes in the vacuole. An animal takes in food as needed and removes wastes through blood and excretory organs, so it has no need of a large storage sac.
Cheap growth. A plant cell enlarges mainly by taking in water into the vacuole rather than by making new cytoplasm — a very economical way to grow.
Flexibility. An animal cell must change shape to move, divide and squeeze past neighbours; a large vacuole would make it stiff.

(ii) Assumptions made:

Both cells are mature and differentiated, not dividing — a meristematic plant cell has no vacuole at all, so if the plant cell were meristematic the answer could change.
The plant cell is a typical living parenchyma-type cell, not a dead cell such as a xylem vessel or sclerenchyma fibre.
The animal cell is an ordinary body cell — not a specialised one such as a fat cell or a large vacuolated secretory cell.
The plant cell is turgid (well supplied with water); a wilted cell has a shrunken vacuole.
“Same size” means the same total cell volume, so we are genuinely comparing the fraction of that volume taken by the vacuole.

Why stating assumptions matters: the answer “plant cell” is only true for the usual, mature case. Naming the assumptions shows exactly when the answer would stop being true — and that is what separates a scientific answer from a memorised one.

Q15.

A textbook states, “Each plant tissue performs only one specific function”. What questions would you ask to critically examine the correctness of this statement? What examples of tissues would you take to find out the answers to these questions?

Answer

The statement is an over-simplification. Specialisation makes one function dominant, but most plant tissues do more than one job.

Questions worth asking:

Does any tissue in the chapter have more than one function listed for it?
Does the same tissue behave differently in different organs, or in different plants?
Does the function change with the age or the condition of the plant?
Can one function be carried out by more than one tissue — that is, is the mapping tissue → function one-to-one at all?
If a tissue really did only one thing, what should we expect to see when it is damaged? Does the plant lose only that one ability?

Examples that answer them:

Tissue	Functions it actually performs	What that shows
Parenchyma	Stores food; photosynthesises in the green parts; forms air spaces that let aquatic plants float; packing tissue	One tissue, at least four jobs — and which one it does depends on where it is
Epidermis	Protection; reduces water loss through the cuticle; absorbs water and minerals as root hair; allows gas exchange and transpiration through stomata	The same tissue is a barrier in one organ and an absorbing surface in another
Xylem	Transports water and minerals; also provides strength to the plant; xylem parenchyma stores food	The book itself gives xylem two functions in the same sentence
Phloem	Transports food; phloem parenchyma stores food, resin, tannins and latex; phloem fibres give strength	A complex tissue divides several functions among its cell types
Lateral meristem	Increases girth; also gives rise to cork cambium, which forms the protective bark	A dividing tissue produces protective tissue as well
Collenchyma and sclerenchyma	Both give mechanical support — one with flexibility, the other with rigidity	Two different tissues share one function, so the mapping is not one-to-one either way

Conclusion. A fairer statement would be: each plant tissue is specialised for a main function, but many tissues perform additional functions as well, and one function may be shared by more than one tissue. And the deepest counter-example is totipotency itself — a mature phloem cell, whose "one function" is food transport, can be made to regenerate an entire carrot plant.

Tip: to test any sweeping statement in science, do not argue with it — look for a single clear counter-example. Parenchyma alone is enough to disprove this one.

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