BharatNotes Why this chapter matters for UPSC: Prelims general science asks plant structure in many forms: which tissue carries food, which roots breathe, which hormone ripens fruit, why maize outperforms other crops in heat. Every one of those questions rests on this chapter's simple picture of root, stem, leaf and flower. In NCERT's rationalised 2023-24 edition it is Chapter 4, "Getting to Know Plants", with the text unchanged apart from chapter cross-references.
🧠 First Principles — Read This First
NCERT begins with a nature walk: some plants are small, some very big, some just patches of green; some have red leaves, some huge flowers, some none at all. To make sense of this variety, the chapter looks at the parts every flowering plant shares and asks what each part does.
- The root holds the plant in the soil and absorbs water and minerals.
- The stem carries water up to the leaves and food from the leaves to other parts: "a street with two-way traffic".
- The leaf makes food by photosynthesis and gives out water vapour by transpiration.
- The flower has sepals, petals, stamens and a pistil; its function, and fruits, come in higher classes.
Two links run through the chapter: plants are grouped by height, nature of stem and branching (herbs, shrubs, trees); and the venation of a leaf tells you the type of root without digging the plant out.
PART 1 — Quick Reference
Herbs, Shrubs, Trees, Creepers, Climbers (NCERT definitions)
| Type | NCERT description | Examples |
|---|---|---|
| Herb | Green and tender stem; usually short; may not have many branches | Weeds with soft stems, many grasses |
| Shrub | Branches near the base of the stem; stem hard but not very thick | Rose, hibiscus |
| Tree | Very tall, with a hard and thick stem; branches in the upper part, much above the ground | Mango, neem |
| Creeper | Weak stem that cannot stand upright; spreads on the ground | Pumpkin, watermelon |
| Climber | Weak stem that takes support and climbs up | Money plant, beanstalk, gourds, grape vine |
NCERT gives no height limits: the groups rest on the nature of the stem and where the branches start.
Parts of a Plant and Their Functions
| Part | Function (NCERT Class VI) | Added detail (higher NCERT classes) |
|---|---|---|
| Root | Absorbs water and minerals; anchors the plant firmly in the soil | Also stores reserve food and synthesises plant growth regulators (Class XI) |
| Stem | Bears leaves, branches, buds, flowers and fruits; conducts water up and food from leaves to other parts | Xylem carries water and minerals; phloem carries food both up and down (Class X) |
| Leaf | Makes food by photosynthesis; gives out water vapour (transpiration) | Stomata, opened and closed by guard cells, let gases in and out (Class X) |
| Flower | Sepals, petals, stamens, pistil | After fertilisation the ovary becomes the fruit and the ovules become seeds (Class VII) |
Venation and Roots Go Together
| Leaf venation | Root type | NCERT examples |
|---|---|---|
| Reticulate (net-like on both sides of the midrib) | Taproot (a main root with smaller lateral roots) | Gram, tulsi, coriander, China rose |
| Parallel (veins parallel to one another) | Fibrous roots (no main root; all roots similar) | Grass, maize, wheat |
Boojho's "brilliant idea": to know a plant's roots, look at its leaves.
Parts of a Flower
| Part | What NCERT says |
|---|---|
| Sepals | Small leaf-like structures; the most prominent part of a closed bud |
| Petals | Different colours in different flowers; inside the sepals |
| Stamen | Two parts: filament and anther |
| Pistil | The innermost part: stigma, style and ovary (the lowermost, swollen part) |
| Ovules | Small bead-like structures inside the ovary |
The structure of a flower is not always the same: the numbers of sepals, petals, stamens and pistils differ, and some parts may be absent.
PART 2 — Concepts & Narrative
The Stem: A Street with Two-Way Traffic
NCERT puts the base of a cut stem in water coloured with red or blue ink. The colour rises in the stem and, after a while, appears in the veins of the leaves: the stem helps in the upward movement of water, and the water and minerals reach the leaves and other parts attached to the stem. The food the leaves make travels the other way.
NCERT Class X names the two tissues. Xylem carries water and minerals from the roots. The products of photosynthesis are moved by translocation in the phloem, through sieve tubes helped by companion cells, "both in upward and downward directions", to the storage organs of roots, fruits and seeds and to growing organs. Unlike xylem transport, which simple physical forces largely explain, phloem translocation uses energy.
The Leaf: Transpiration and Photosynthesis
A leaf is attached to the stem by the petiole; its broad green part is the lamina; the prominent line in the middle is the midrib, and the lines are veins. Their design is the venation: reticulate or parallel.
Transpiration (NCERT activity): tie a polythene cover around a leafy branch of a well-watered plant in the sun, and another around nothing as a control. After a few hours droplets of water appear inside the first cover. Water comes out of leaves as vapour; plants release a lot of water into the air this way.
How transpiration lifts water (NCERT Class X): evaporation of water from the cells of a leaf creates a suction that pulls water up from the xylem cells of the roots. Transpiration therefore helps the absorption and upward movement of water and minerals, and it also helps in temperature regulation. Root pressure matters more at night; during the day, when the stomata are open, the transpiration pull is the main driving force.
Stomata: tiny pores on the leaf through which gases are exchanged. Each pore is bordered by guard cells: they swell when water flows into them, opening the pore, and shrink to close it.
Photosynthesis (NCERT activity): boil a leaf in spirit (in a test tube placed in hot water) until its green colour comes out, wash it and pour iodine solution on it. It turns blue-black: the leaf contains starch. Leaves prepare food in the presence of sunlight and a green-coloured substance (chlorophyll), using water and carbon dioxide; oxygen is given out. The food is stored in different parts of the plant: a raw potato also tests positive for starch, which it gets from the leaves.
Forests as carbon stores (official figures):
- India State of Forest Report 2023 (released 21 December 2024): total carbon stock in the country's forests is 7,285.5 million tonnes, up 81.5 million tonnes from the previous assessment. Expressed as CO₂ equivalent it is 30.43 billion tonnes.
- NDC target for 2030 (updated NDC approved by the Union Cabinet on 3 August 2022, retaining India's 2015 commitment): an additional carbon sink of 2.5 to 3 billion tonnes of CO₂ equivalent through additional forest and tree cover. ISFR 2023 reports 2.29 billion tonnes already reached against the 2005 base.
- NDC for 2031-35 (approved by the Union Cabinet on 25 March 2026): a sink of 3.5 to 4.0 billion tonnes of CO₂ equivalent through forest and tree cover by 2035, from the 2005 level.
Every tonne in these figures was fixed by photosynthesis in leaves.
The Root: Anchor and Water Pump
NCERT's pot experiment: plant one plant with roots and one without, water both regularly, and after a week only the rooted plant is healthy. Seeds of gram and maize grown on wet cotton cling to it: roots hold the plant firmly in the soil. NCERT names two types: a taproot (a main root with smaller lateral roots) and fibrous roots (no main root, all roots similar). Gram has a taproot, maize fibrous roots.
NCERT Class XI adds the details. In monocotyledons the primary root is short-lived and is replaced by many roots from the base of the stem: the fibrous system of wheat. In grass, Monstera and the banyan, roots arise from parts of the plant other than the radicle: adventitious roots. Root hairs, very fine thread-like outgrowths in the region of maturation, absorb water and minerals.
Modified roots and stems (NCERT Class XI, 2021-22 edition)
| Modification | Function | Examples named by NCERT |
|---|---|---|
| Swollen taproots | Store food | Carrot, turnip |
| Swollen adventitious roots | Store food | Sweet potato |
| Prop roots | Support | Hanging roots of the banyan |
| Stilt roots | Support, from the lower nodes of the stem | Maize, sugarcane |
| Pneumatophores | Grow vertically up out of swampy ground to get oxygen for respiration | Rhizophora (a mangrove) |
| Underground stems | Store food; survive unfavourable seasons | Potato, ginger, turmeric, zaminkand, colocasia |
| Stem tendrils | Slender, coiled, from axillary buds; help the plant climb | Gourds, grapevine |
Prelims trap: a potato is a stem and a sweet potato is a root. NCERT Class VI lists the roots we eat as carrot, radish, sweet potato, turnip and tapioca.
The Flower, and What Happens Next (NCERT Class VII)
NCERT Class VI asks students to open a flower, count its parts, and cut the ovary to find the ovules, leaving the function of flowers for later. NCERT Class VII supplies it:
- Pollination is the transfer of pollen from the anther to the stigma. Self-pollination: pollen lands on the stigma of the same flower, or of another flower on the same plant. Cross-pollination: pollen reaches a flower of a different plant of the same kind. Wind, water and insects carry pollen.
- Fertilisation: a male and a female gamete fuse to form a zygote, which develops into the embryo.
- "Fruit is the mature ovary whereas ovule develops into a seed", which contains the developing embryo.
Seed dispersal (NCERT Class VII) helps plants (i) prevent overcrowding, (ii) avoid competition for sunlight, water and minerals and (iii) invade new habitats.
| Agent | NCERT examples |
|---|---|
| Wind | Winged seeds of drumstick and maple; light seeds of grasses; hairy seeds of aak (madar); hairy fruit of sunflower |
| Water | Spongy or fibrous outer coat that floats, as in coconut |
| Animals | Spiny seeds with hooks that catch on animals: Xanthium, Urena |
| Bursting fruit | Fruits burst with sudden jerks: castor, balsam |
Do not confuse the two plants. Balsam scatters its seeds from bursting fruits; NCERT Class VI uses the name "touch-me-not" for Mimosa, whose leaves fold when touched (see The Living Organisms).
Plant Hormones (NCERT Class XI)
NCERT Class XI groups the plant growth regulators (PGRs) into five categories:
| PGR | What NCERT says it does | Uses named by NCERT |
|---|---|---|
| Auxins (IAA, IBA; synthetic NAA, 2,4-D) | Produced at growing apices of stems and roots; cause apical dominance; induce parthenocarpy (tomato); control xylem differentiation | Rooting of stem cuttings; flowering in pineapple; 2,4-D kills dicot weeds but not mature monocots (weed-free lawns) |
| Gibberellins (GA₃ and over 100 others) | Lengthen the axis; delay senescence; cause bolting in beet and cabbage | Longer grape stalks; better-shaped apples; sugarcane yield up "by as much as 20 tonnes per acre"; faster malting in brewing |
| Cytokinins (zeatin, from corn kernels and coconut milk) | Promote cell division, new leaves and chloroplasts; overcome apical dominance; delay leaf senescence | |
| Ethylene | A simple gaseous PGR; promotes senescence, abscission and fruit ripening (raises the respiration rate, the "respiratory climactic") | Flowering in pineapple and mango; ethephon releases ethylene and hastens ripening in tomatoes and apples |
| Abscisic acid (ABA) | General growth inhibitor; inhibits seed germination; closes stomata; raises tolerance to stress, so it is called the "stress hormone" |
Apical dominance: the growing apical bud suppresses the lateral buds. Removing the shoot tip (decapitation) lets the lateral buds grow, which is why it is "widely applied in tea plantations and hedge-making".
Ripening fruit legally (FSSAI, PIB release of 18 May 2024):
- Calcium carbide is banned. It releases acetylene gas carrying traces of arsenic and phosphorus (the "masala" of the trade), which can cause dizziness, vomiting and skin ulcers. Regulation 2.3.5 of the Food Safety and Standards (Prohibition and Restrictions on Sales) Regulations, 2011 forbids selling fruit "artificially ripened by use of acetylene gas, commonly known as carbide gas".
- Ethylene gas is permitted at concentrations up to 100 ppm, depending on crop, variety and maturity, following FSSAI's guidance document "Artificial Ripening of Fruits: Ethylene gas a safe fruit ripener".
- The Central Insecticides Board and Registration Committee has approved Ethephon 39% SL for uniform ripening of mangoes and other fruits.
Acetylene is not ethylene. Ethylene (C₂H₄) is the plant's own hormone; acetylene (C₂H₂) is a different gas that merely mimics its effect, and the carbide that makes it brings toxic impurities.
Growing Plants Without Seeds (NCERT Class X)
In vegetative propagation, parts such as the root, stem or leaves grow into new plants. Layering and grafting raise sugarcane, roses and grapes for agriculture. Such plants bear flowers and fruit earlier than seed-grown ones; the method also propagates plants that have lost the capacity to produce seeds, such as banana, orange, rose and jasmine; and every new plant is genetically similar to the parent. Buds in the notches along a Bryophyllum leaf fall to the soil and grow into new plants; a money-plant cutting with a leaf on it grows roots in water.
Tissue culture: cells from the growing tip are placed in an artificial medium, where they divide into a mass called a callus; moved to a medium with hormones, the callus grows and differentiates into plantlets, which are planted out. Many plants can be raised from one parent in disease-free conditions; NCERT notes the method is common for ornamental plants.
C3 and C4 Plants (NCERT Class XI)
| Feature | C3 plants | C4 plants |
|---|---|---|
| First stable product of CO₂ fixation | 3-carbon PGA | 4-carbon oxaloacetic acid (OAA) |
| Leaf anatomy | No special bundle sheath | Kranz anatomy: large bundle-sheath cells around the vascular bundles ("Kranz" means wreath) |
| Photorespiration | Occurs: RuBisCO binds some O₂ instead of CO₂, a pathway that makes no sugar and no ATP and releases CO₂ | Does not occur: CO₂ is concentrated at the enzyme site |
| Temperature | Lower temperature optimum | Tolerate and respond to higher temperatures |
| Productivity | Lower | Greater productivity of biomass |
| Response to more CO₂ | Photosynthesis rises up to beyond 450 µL/L, so CO₂-enriched greenhouses raise tomato and bell pepper yields | Saturate at about 360 µL/L |
| NCERT examples | Maize, sorghum |
C4 plants still use the C3 (Calvin) cycle as their main biosynthetic pathway; the C4 step is a front end that delivers concentrated CO₂ to it.
PART 3 — UPSC Integration
The chapter's root-stem-leaf-flower scheme is the scaffolding for most of plant biology in the syllabus. Roots explain soil binding and the special roots of mangroves; the two-way traffic of the stem explains why girdling a tree kills it and how food reaches tubers, fruits and seeds; stomata and transpiration explain water loss and the cooling of leaves; photosynthesis connects leaves to food security and to the forest carbon stock India counts towards its climate pledges. The hormones explain everyday agricultural practice, from rooting powders to the ban on carbide-ripened mangoes, and C4 biology explains why maize and sorghum handle heat better. Questions are usually factual in Prelims and applied in Mains: always name the plant part or process, then the example.
Exam Strategy
Prelims traps:
- Herb, shrub, tree are defined by the stem and branching, not by fixed heights.
- Reticulate venation goes with taproots; parallel venation with fibrous roots.
- Phloem moves food both up and down; xylem moves water and minerals from the roots.
- Potato = underground stem; sweet potato = adventitious root; carrot, turnip = taproots.
- Pneumatophores (mangroves such as Rhizophora) are for respiration; prop roots (banyan) and stilt roots (maize, sugarcane) are for support.
- Fruit = mature ovary; seed = ovule.
- Ethylene is the only gaseous PGR in NCERT's five; ABA is the stress hormone that closes stomata; cytokinins overcome apical dominance.
- Calcium carbide gives acetylene, not ethylene, and its use is banned (FSS Regulation 2.3.5, 2011).
- C4: first product OAA, Kranz anatomy, no photorespiration; NCERT's examples maize and sorghum.
Mains angle: Explain how transpiration moves water up a tree and why stomata close in drought; or explain why carbide ripening is banned while ethylene ripening is allowed.
Practice Questions
Practice (UPSC-pattern, not past papers).
Prelims:
A plant has leaves with parallel venation. Its roots are most likely:
(a) A taproot with lateral roots
(b) Fibrous roots
(c) Prop roots
(d) PneumatophoresConsider the following statements about transport in plants:
- Xylem carries water and minerals from the roots.
- Phloem carries food only downwards, from leaves to roots.
- Transpiration pull is the main force moving water in xylem during the day.
Which of the statements given above are correct?
(a) 1 and 2 only
(b) 1 and 3 only
(c) 2 and 3 only
(d) 1, 2 and 3
- Xylem carries water and minerals from the roots.
Which one of the following is a modified stem?
(a) Sweet potato
(b) Carrot
(c) Potato
(d) TurnipWhich plant growth regulator is called the "stress hormone" because it closes stomata?
(a) Auxin
(b) Gibberellin
(c) Cytokinin
(d) Abscisic acidWith reference to the artificial ripening of fruit in India, consider the following statements:
- Fruit ripened with acetylene gas from calcium carbide may not be sold.
- Ethylene gas is permitted for ripening at concentrations up to 100 ppm.
- Acetylene and ethylene are the same compound.
Which of the statements given above are correct?
(a) 1 and 2 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1, 2 and 3
- Fruit ripened with acetylene gas from calcium carbide may not be sold.
Which of the following is a feature of C4 plants?
(a) The first product of CO₂ fixation is a 3-carbon compound
(b) High rates of photorespiration
(c) Kranz anatomy with large bundle-sheath cells
(d) A lower temperature optimum than C3 plantsSeeds of castor and balsam are dispersed by:
(a) Wind
(b) Water
(c) Animals
(d) Bursting of the fruit
Mains (UPSC-pattern):
- Explain how water reaches the top of a tall tree and why plants close their stomata during drought. (150 words)
- "C4 plants are better suited to a warming world." Examine with reference to photorespiration and temperature. (150 words)
📦 Revision Capsule
Hard Facts
- Herb: green, tender stem; shrub: branches near the base, hard but not thick stem; tree: tall, hard thick stem, branches high up; creeper spreads on the ground; climber takes support
- Leaf: petiole + lamina; midrib, veins, venation (reticulate or parallel)
- Reticulate ↔ taproot; parallel ↔ fibrous roots
- Roots absorb water and minerals and anchor the plant; eaten roots: carrot, radish, sweet potato, turnip, tapioca
- Flower: sepals, petals, stamens (filament + anther), pistil (stigma + style + ovary with ovules)
- Photosynthesis: leaves + sunlight + chlorophyll + water + CO₂ → food (starch test with iodine) + oxygen
- ISFR 2023: forest carbon stock 7,285.5 Mt; NDC sink targets 2.5-3 bn t CO₂e by 2030 (2022 NDC) and 3.5-4.0 bn t by 2035 (2031-35 NDC)
Core Concepts
- Stem = two-way traffic: water up in xylem; food up and down in phloem
- Transpiration pull lifts water by day; root pressure matters at night; guard cells open and close stomata
- Fruit = mature ovary; seed = ovule; dispersal avoids overcrowding and competition and colonises new habitats
- Five PGRs: auxins, gibberellins, cytokinins, ethylene (gaseous), ABA (stress)
- C4 plants: OAA, Kranz anatomy, no photorespiration, heat-tolerant, more biomass
Confused Pairs
- Taproot (gram) vs fibrous (maize) vs adventitious (banyan, grass)
- Potato (stem) vs sweet potato (root)
- Prop roots (banyan) vs stilt roots (maize, sugarcane) vs pneumatophores (Rhizophora)
- Self-pollination (same flower or plant) vs cross-pollination (another plant of the same kind)
- Ethylene (hormone, permitted ripener) vs acetylene (carbide gas, banned)
PYQ Pattern
- No question in BharatNotes' PYQ bank tests this chapter directly. Expect Prelims general science on plant parts and tissues, root and stem modifications, plant hormones, C3/C4 plants and the regulation of fruit ripening.
Sources
Sources
- NCERT, Science (Class VI), ch. 7 "Getting to Know Plants" (2020-21 print) and ch. 4 in the Rationalised 2023-24 edition: NCERT's book archives as captured by the Wayback Machine, 2020 copy and 2023-24 copy.
- NCERT, Science (Class VII), ch. 8 "Reproduction in Plants", Reprint 2024-25: book archive.
- NCERT, Science (Class X), ch. 5 "Life Processes" and ch. 7 "How do Organisms Reproduce?", Reprint 2025-26: book archive.
- NCERT, Biology (Class XI), ch. 5 "Morphology of Flowering Plants" (2021-22 print, for root and stem modifications), ch. 11 "Photosynthesis in Higher Plants" and ch. 13 "Plant Growth and Development" (Reprint 2025-26 book).
- PIB (Ministry of Environment, Forest and Climate Change), Union Minister releases India State of Forest Report 2023, 21-Dec-2024.
- PIB (Cabinet), Cabinet approves India's updated Nationally Determined Contribution, 3-Aug-2022; PIB (Cabinet), Cabinet approves India's Nationally Determined Contribution for 2031 to 2035, 25-Mar-2026.
- PIB (Ministry of Health and Family Welfare), FSSAI alerts fruit traders to ensure compliance with prohibition of calcium carbide in fruit ripening, 18-May-2024.
