Seeds: Structure and Germination ICSE Class 9: Bean, Maize, Epigeal and Hypogeal Germination

What Seeds: Structure and Germination is about

Weightage: CISCE publishes no chapter weightage for ICSE Biology. Seeds: Structure and Germination is topic 3, Plant Physiology (i), of the Class IX part of the 2028 syllabus; the Class IX paper (80 marks, 2 hours) is set and marked by the school.Source: CISCE ICSE Biology (Science Paper 3) syllabus, examination year 2028 (Class IX)

Key concepts

Structure of a bean seed (dicot)

External features (soak a bean seed overnight):

• Seed coat of two layers: outer, tough testa and inner, thin tegmen.
• Hilum: an oval scar where the seed was attached to the fruit wall by its stalk.
• Micropyle: a tiny pore near the hilum; it lets in water at germination (squeeze a soaked seed and water bubbles out here).

Internal structure (remove the seed coat): the embryo, made of:

• Two cotyledons (seed leaves): large, fleshy, store food (mainly starch and protein); the endosperm has been absorbed, so the bean is non-endospermic (exalbuminous).
• Embryonal axis between them:
• Radicle: points towards the micropyle; grows into the root.
• Plumule: lies between the cotyledons with tiny folded leaves; grows into the shoot.
• Hypocotyl: part of the axis below the point of attachment of the cotyledons.
• Epicotyl: part above the cotyledons, up to the plumule.

Worked example

Why does a soaked bean seed release a bubble of water from one spot when squeezed?

Try it first, then show the solutionSolution

1. Water entered the seed mainly through the micropyle.
2. Pressing pushes it back out through the same pore.

Answer: Through the micropyle.

Structure of a maize grain (monocot)

A maize grain is strictly a one-seeded fruit: its fruit wall (pericarp) is fused with the seed coat, so there is no separate hilum or micropyle to see.

Cut lengthwise, it shows:

• Endosperm: a large food store (mainly starch), so maize is endospermic (albuminous). It turns blue-black with iodine.
• Aleurone layer: a thin protein-rich layer just under the seed coat around the endosperm.
• Embryo, at one side of the narrower end:
• Scutellum: the single cotyledon, shield-shaped, pressed against the endosperm; it absorbs food from the endosperm for the growing embryo.
• Plumule covered by a protective sheath, the coleoptile.
• Radicle covered by a protective sheath, the coleorhiza.

Worked example

A cut maize grain is tested with iodine. Which part turns blue-black, and what does this show?

Try it first, then show the solutionSolution

1. The endosperm turns blue-black.
2. Iodine turns blue-black with starch, so the endosperm stores starch.

Answer: Endosperm; it stores starch.

Monocot versus dicot seeds

Feature	Dicot seed (bean)	Monocot seed (maize)
Cotyledons	two	one (scutellum)
Endosperm	usually absent (non-endospermic)	present, large (endospermic)
Main food store	cotyledons	endosperm
Seed coat	separate from fruit wall; hilum and micropyle visible	fused with fruit wall (pericarp)
Protective sheaths	none on plumule or radicle	coleoptile over plumule, coleorhiza over radicle
Examples	bean, pea, gram, castor (endospermic dicot)	maize, wheat, rice

Note: castor is a dicot with endosperm, so 'dicot = no endosperm' is not always true.

Worked example

Which part of a bean seed does the job that the endosperm does in maize?

Try it first, then show the solutionSolution

1. In maize the endosperm stores food.
2. In bean the endosperm is absorbed into the cotyledons, which store the food.

Answer: The cotyledons.

Germination: epigeal and hypogeal

Germination is the process by which the embryo of a seed grows into a seedling, once dormancy ends and conditions are suitable.

Steps: the seed absorbs water (imbibition) and swells; the seed coat bursts; enzymes become active and stored food is digested; the radicle emerges first and grows down into the soil; then the plumule grows up.

	Epigeal germination	Hypogeal germination
Cotyledons	brought above the soil	remain below the soil
Part that elongates	hypocotyl	epicotyl
Cotyledons above ground	turn green and photosynthesise for a short time, then fall	stay in soil, supply food, then shrivel
Examples	bean, castor, sunflower, papaya, cotton	pea, gram, maize, wheat, rice

In maize, the coleoptile pushes through the soil first, protecting the plumule; the radicle breaks out through the coleorhiza.

Worked example

In a germinating bean, the stem below the cotyledons forms a hook as it pushes up. Why is this useful?

Try it first, then show the solutionSolution

1. The hypocotyl grows and arches.
2. The arch pushes through the soil, pulling the delicate plumule and cotyledons up behind it, so they are not damaged.

Answer: It protects the plumule while breaking through the soil.

Conditions for germination and experiments

A seed needs three external conditions:
1. Water: softens the seed coat, makes the seed swell and burst the coat, activates enzymes that digest stored food, and lets food dissolve and move to the growing embryo.
2. Oxygen (air): for aerobic respiration, which releases the energy for growth.
3. Suitable temperature (moderate warmth, roughly 25-35 °C for most seeds): enzymes work best in this range; too cold or too hot stops or kills them.

Also internal conditions: the embryo must be alive (viable), have enough stored food, and the seed must be past any dormancy. Most seeds do not need light to germinate.

Experiment 1: the three-bean experiment (water and air)

• Tie three soaked bean seeds on a glass rod in a beaker: top seed above water, middle seed at the water surface, bottom seed under water. (Use boiled, cooled water topped with a thin layer of oil to keep air out of the water.) Keep warm for a few days.
• Result: only the middle seed germinates. Top: air but no water. Bottom: water but too little oxygen.

Experiment 2: temperature

• Keep two similar sets of soaked seeds with moist cotton, one in a refrigerator (about 4 °C) and one in a warm room.
• Result: only the warm set germinates.

Experiment 3: oxygen

• Two flasks with moist seeds; one also contains alkaline pyrogallol (absorbs oxygen), the other plain water or KOH alone (control). Seal both.
• Result: seeds without oxygen do not germinate.

Worked example

In the three-bean experiment, why is the water boiled and covered with oil?

Try it first, then show the solutionSolution

1. Boiling removes dissolved air (oxygen) from the water.
2. The oil layer stops air dissolving back in.
3. So the bottom seed truly has water but no oxygen.

Answer: To remove and keep out dissolved oxygen.

Seeds: Structure and Germination in real life

Each concept, met in an everyday situation. Read the situation, answer the question in your own words, then compare with the model answer. The one-line hook is what to remember.

Topics in this chapter

• Seed Structure, Types and Germination Conditions

Seeds: Structure and Germination: key facts

Bean embryo

$\text{embryo}=2\text{cotyledons}+\text{radicle}+\text{plumule}+\text{hypocotyl}+\text{epicotyl}$

Non-endospermic dicot.

Maize embryo

$\text{embryo}=\text{scutellum}+\text{plumule (coleoptile)}+\text{radicle (coleorhiza)}$

Endosperm separate.

Germination needs

$\text{water}+\text{oxygen}+\text{suitable temperature}$

Plus a viable embryo.

Germination percentage

$\%=\frac{\text{seeds germinated}}{\text{seeds sown}}\times 100$

Seed quality test.

Seeds: Structure and Germination: diagrams to practise

Practise each one on paper: draw it from the checklist, then tick off every label.

How the school exam asks Seeds: Structure and Germination

The question patterns to expect, and the method that works for each.

Tricks to remember Seeds: Structure and Germination

Short memory aids. Say each one aloud once, then use it on a question the same day.

• Epi = above, hypo = below

  Epi = above: epigeal lifts cotyledons above ground (hypocotyl grows). Hypo = below: hypogeal keeps them below (epicotyl grows).

  Use it when: Types of germination.

• Bean up, pea down

  Bean is epigeal; pea is hypogeal; maize is hypogeal.

  Use it when: Examples.

• 'WOT' a seed needs

  Water, Oxygen, Temperature.

  Use it when: Conditions for germination.

• Coleoptile = cap on the plumule; Coleorhiza = cap on the root

  Rhiza means root.

  Use it when: Maize grain parts.

Seeds: Structure and Germination: exam-level solved questions

Ordered from exam level to HOTS. Cover the solution, write your own, then compare step by step.

Case-study practice (Section B style)

Read the situation, then answer every part. In a school exam set on the board pattern this is a 5-mark question split into 2 + 2 + 1 marks.

Where the marks are

How a typical answer is split into step marks. Show every step: a right final answer alone rarely earns full marks.

Where students lose marks in Seeds: Structure and Germination

The slips examiners see most often, and what to write instead.

• ✗Mistake: Hypocotyl and epicotyl swapped

  The prefixes are mixed up.

  Wrong working

  In epigeal germination the epicotyl elongates.

  Right working

  Epigeal: hypocotyl elongates (lifts cotyledons). Hypogeal: epicotyl elongates.

  ✓Do this: The part that grows is the 'opposite' word.

  Usually costs: 1 mark.

• ✗Mistake: Saying maize has a hilum and micropyle visible

  Maize is treated like a bean seed.

  Wrong working

  Label 'micropyle' on the outer surface of a maize grain.

  Right working

  The seed coat is fused with the fruit wall; hilum and micropyle are not seen.

  ✓Do this: Remember maize grain is a fruit.

  Usually costs: 1 mark.

• ✗Mistake: Listing light as a condition

  Students confuse germination with photosynthesis.

  Wrong working

  Seeds need sunlight to germinate.

  Right working

  Water, oxygen and suitable temperature; most seeds do not need light.

  ✓Do this: Light is needed later for the seedling to make food.

  Usually costs: 1 mark.

• ✗Mistake: Experiment without a control or reason

  Answers describe the set-up but not why each seed fails.

  Wrong working

  The bottom seed did not germinate.

  Right working

  The bottom seed did not germinate because, under boiled water with oil, it had no oxygen.

  ✓Do this: Give result + reason + conclusion.

  Usually costs: 1-2 marks.

Practice questions on Seeds: Structure and Germination

Write each answer on paper first. Open the hint only if you are stuck, and the answer only when you have finished.

1. Q1 · 1 mark · MCQExam level

   Epigeal germination is seen in:
   (a) pea
   (b) maize
   (c) bean
   (d) wheat

   Hint

   Cotyledons above soil.

   Answer

   (c)

2. Q2 · 1 mark · MCQExam level

   The part of the maize grain that turns blue-black with iodine is the:
   (a) scutellum
   (b) endosperm
   (c) coleoptile
   (d) radicle

   Hint

   Starch store.

   Answer

   (b)

3. Q3 · 3 marks · Very short answerExam level

   Name: (a) the outer layer of the bean seed coat, (b) the protein-rich layer in maize, (c) the part of the bean embryo above the cotyledons.

   Hint

   Testa; aleurone; epicotyl.

   Answer

   (a) Testa (b) Aleurone layer (c) Epicotyl

4. Q4 · 2 marks · Short answerExam level

   Give two reasons why water is needed for germination.

   Hint

   Softening; enzymes.

   Answer

   It softens the seed coat so it bursts; it activates enzymes that digest stored food (and dissolves food for transport).

5. Q5 · 2 marks · Short answerHarder exam level

   Why are the cotyledons of a bean seedling green while those of a pea seedling are not?

   Hint

   Light.

   Answer

   Bean is epigeal: its cotyledons come above the soil into light and form chlorophyll. Pea is hypogeal: its cotyledons stay underground in darkness.

6. Q6 · 2 marks · Short answerHarder exam level

   Explain the role of the scutellum in a germinating maize grain.

   Hint

   Absorbs food.

   Answer

   The scutellum (cotyledon) lies against the endosperm; it absorbs digested food from the endosperm and passes it to the growing embryo.

7. Q7 · 3 marks · Short answerHarder exam level

   Describe an experiment to show that a suitable temperature is needed for germination. Give the control and the result.

   Hint

   Refrigerator.

   Answer

   Place two sets of soaked seeds on moist cotton in two dishes; keep one in a refrigerator (about 4 °C) and one at room temperature (control). After a few days only the room-temperature set germinates, showing warmth is needed.

8. Q8 · 2 marks · Short answerHarder exam level

   Seeds sown too deep in soil often fail to come up. Give two reasons.

   Hint

   Oxygen; food store.

   Answer

   Less oxygen reaches them deep in the soil; the stored food may be used up before the shoot reaches light to start photosynthesis.

9. Q9 · 2 marks · Short answerHarder exam level

   Why do the seeds of a plant need a seed coat, and why must it burst at germination?

   Hint

   Protection; growth.

   Answer

   The coat protects the embryo from injury, drying and microbes. It must burst so that the radicle and plumule can grow out.

10. Q10 · 3 marks · Short answerHOTS / competency

    200 bean seeds are sown and 170 germinate. Find the germination percentage. If a farmer needs 3400 plants, how many seeds should he sow (assume the same percentage)?

    Hint

    Divide by the fraction.

    Answer

    170/200 × 100 = 85%. Seeds = 3400 ÷ 0.85 = 4000.

11. Q11 · 3 marks · Short answerHOTS / competency

    A student finds that seeds kept on moist cotton in a closed, airtight jar germinate for a day and then stop growing, while those in an open dish keep growing. (a) Which condition became limiting? (b) Why did they start at all? (c) How could you prove your answer?

    Hint

    Oxygen used up.

    Answer

    (a) Oxygen. (b) The jar at first contained some air, enough for a little respiration. (c) Repeat with an airtight jar containing alkaline pyrogallol (no germination at all) and one with a larger air volume or fresh air pumped in (longer growth).

Test your recall

Answer in your head or on paper first, then open the card. Pulling an answer out of memory makes it stick far better than re-reading.

1. 1.Scar on the seed coat where the seed was attached?Show answer

   Hilum.

2. 2.Part of the embryo that forms the root?Show answer

   Radicle.

3. 3.Sheath over the maize radicle?Show answer

   Coleorhiza.

4. 4.Part that elongates in hypogeal germination?Show answer

   Epicotyl.

5. 5.Type of germination in maize?Show answer

   Hypogeal.

6. 6.Food store of the maize grain?Show answer

   Endosperm.

7. 7.Chemical used to absorb oxygen in a germination experiment?Show answer

   Alkaline pyrogallol.

8. 8.Three external conditions for germination?Show answer

   Water, oxygen, suitable temperature.

Quick revision checklist

The night before the exam: can you do each of these without looking?

• ☐Can you label a bean seed and a maize grain?
• ☐Can you give the function of each part?
• ☐Can you write three monocot-dicot seed differences?
• ☐Can you compare epigeal and hypogeal germination?
• ☐Can you describe the three-bean experiment and explain each result?

Seeds: Structure and Germination: frequently asked questions