What Is A Plant?

Plant

A living organism, usually green and rooted in soil, that makes its own food through photosynthesis.

Photosynthesis

Photosynthesis

Process where green plants make food using sunlight, carbon dioxide and water, releasing oxygen.

Key Characteristics:

  • Needs sunlight, chlorophyll, CO₂, and water.
  • Makes glucose for the plant’s food.
  • Releases oxygen into the air.

Example:

A sunflower uses photosynthesis to turn sunlight into sugar.

Parts of a Plant

Parts of a Plant

Locate Each Part

A plant’s structure has four main parts you can spot easily.

Key Points:

  • Root – holds plant in soil and soaks up water and minerals.
  • Stem – lifts leaves and moves water and food around the plant.
  • Leaf – uses sunlight to make food by photosynthesis.
  • Flower – produces pollen and turns into seeds and fruit.

Seed to Plant

Trace each stage of seed germination, from water uptake to a self-feeding seedling.

1

Water Uptake

The dry seed soaks water; cells swell and wake.

2

Seed Coat Splits

Pressure breaks the seed coat, letting the radicle push out.

3

Shoot Rises

Plumule grows upward, seeking light above the soil.

4

First Leaves

Cotyledons or first leaves turn green and start photosynthesis.

Pro Tip:

Keep soil moist, not waterlogged, so oxygen and water reach the seed.

Water Path

Follow how water is transported from root to leaf.

Roots
Stem
(xylem)
Leaves
Evaporation
transport

Legend:

Start/End
Decision
Process

Food Equation

\[6CO_{2} + 6H_{2}O \rightarrow C_{6}H_{12}O_{6} + 6O_{2}\]

(in sunlight, with chlorophyll)

Variable Definitions

CO₂ Carbon dioxide from air
H₂O Water from soil
C₆H₁₂O₆ Glucose (food)
O₂ Oxygen released

Applications

Plant Food

Glucose helps the plant grow and store energy.

Oxygen Supply

Released oxygen is vital for animals and humans to breathe.

Source: NCERT Class 7 Science

Why Oxygen Out?

1
\[h\nu\]

Chlorophyll grabs sunlight, kicking off the light reaction.

2
\[2H_{2}O \;\rightarrow\; 4H^{+}+4e^{-}+O_{2}\]

Captured energy splits water; protons and electrons stay, oxygen forms.

3
\[O_{2}\uparrow\]

Freshly made oxygen diffuses out through stomata into the air.

Key Insight:

Oxygen we breathe comes from the reaction step that splits water; tracking O2 shows the light reaction is working.

Leaf Test

Setup & Conditions

  1. Expose leaf to sunlight for 4 h.
  2. Boil leaf in water for 2 min.
  3. Heat in hot alcohol to remove chlorophyll.
  4. Rinse, place on white tile, add iodine.
  5. Note any blue-black colour.

Materials

  • Fresh leaf
  • Beaker & hot water
  • Alcohol bath
  • Iodine solution
  • White tile & forceps

Raw Data

Leaf region Colour after iodine Starch present
Green areas _____ Yes / No
Non-green areas _____ Yes / No

Observations & Notes

Record which regions turn blue-black. Blue-black shows starch, proving photosynthesis occurred there.

What We Learned

Inference

Conclusion: Blue-black colour confirms the leaf stored starch, so photosynthesis happened.

Supporting Evidence

Iodine test turned the leaf blue-black.
Starch forms only after photosynthesis.

Confidence Level

High Confidence
Based on multiple evidence points

Root Types — Taproot vs Fibrous

Taproot

One thick main root grows straight down.
Lateral branches are thinner side roots.
Reaches deep water sources.
Seen in dicots like carrot and mustard.

Fibrous Root

Many thin roots arise from stem base.
Form a dense, bushy network.
Spread near soil surface, prevent erosion.
Common in monocots like wheat and grass.

Key Similarities

Anchor the plant firmly.
Absorb water and minerals from soil.
Transport nutrients upward to the stem.

Part Functions

Plant Part Main Function
Root Absorbs water & minerals
Stem Carries water, minerals & food
Leaf Prepares food by photosynthesis
Flower Enables reproduction

Sunlight vs Growth

Key Insights

Plant height rises as daily sunlight grows from 0–8 h.

After ~8 h, the line flattens; extra light adds little height.

Reading the chart shows 6–8 h gives almost maximum growth.

Legend

Average plant height

Data Source

Grade 7 classroom experiment

Key Takeaways

Plant Parts

Roots, stem, leaves and flowers form the basic body of a plant.

Photosynthesis

Leaves prepare food using sunlight, water and carbon dioxide.

Water Transport

Xylem in the stem moves water from roots to leaves.

Root Types

Taproot and fibrous roots anchor plants and absorb water.

Remember This

Main Points

  1. 1 Plants make their own food.
  2. 2 Sunlight provides the needed energy.
  3. 3 Roots absorb water and minerals.
  4. 4 Plants release oxygen into the air.

Key Highlights

  • Food factory: photosynthesis.
  • Sun is the energy source.
  • Roots bring in water.
  • Plants give us oxygen.
"The clearest way into the Universe is through a forest."
J

John Muir

May this thought motivate you to care for every plant, knowing each leaf links us to the wider universe.

Riya’s Wilted Tomato

Scenario

At noon, Riya sees her tomato plant’s leaves droop and lose shine. The sun is harsh, and the soil feels dry. She hopes to revive it quickly.

Challenge Question

Apply your knowledge of plant water needs: What simple step can stop the midday wilting?

Characters

R

Riya

Young gardener

"My tomato looks so tired at lunchtime!"

Meet The Helpers

R

Riya

Caring plant owner

"These leaves are like my pets!"

G

Grandpa

Wise gardener & mentor

"Plants speak if you watch closely."

A

Amit

Curious science buddy

"Let's test how light helps them grow!"

Multiple Choice Question

Question

Which part of a plant prepares its food?

1
Root
2
Leaf
3
Stem
4
Flower

Match Part & Job

Drag each plant part to the box that describes its function.

Draggable Items

Root
Stem
Leaf
Flower

Drop Zones

Anchors plant & absorbs water

Moves water and food

Prepares food

Forms seeds for reproduction

Tip:

Think about what each part does in a healthy plant.

You Did It!

Identified key plant parts: roots, stem, leaves, flowers.

Explored plant processes: photosynthesis, transpiration, reproduction.

Performed simple experiments to show what plants need.

You can now explain plant basics with confidence.

Next Steps

Observe a nearby plant and match each part to its job.

Thank You!

We hope you found this lesson informative and engaging.

Solved Example

Photosynthesis Word Problem

Problem Statement

A plant uses 12 molecules of carbon dioxide during photosynthesis. Determine how many oxygen molecules it releases.

No diagram needed

Solution Process

1

Recall balanced equation

Photosynthesis: 6 molecules of CO₂ and 6 of H₂O form glucose and 6 molecules of O₂.

\(6\text{CO}_2 + 6\text{H}_2\text{O} \rightarrow C_6H_{12}O_6 + 6\text{O}_2\)

2

Find mole ratio

The balanced equation shows a 1 : 1 ratio between CO₂ and O₂.

\(\frac{6\text{O}_2}{6\text{CO}_2}=1\)

Key Insight

A balanced chemical equation gives direct mole ratios, letting us convert quantities quickly.

3

Apply to given amount

Using the 1 : 1 ratio, 12 molecules of CO₂ release 12 molecules of O₂.

\(12\text{CO}_2 \times 1 = 12\text{O}_2\)

Final Answer

The plant releases 12 molecules of O₂.

Each CO₂ used yields one O₂, so the numbers are equal.

Additional Notes

Common Mistakes

  • Using an unbalanced equation.
  • Mixing up reactant–product coefficients.

Related Topics

  • Plant respiration
  • Law of conservation of mass

Try This

Class 7 Science • Plant Life

Question

Why do leaves look green?

Progressive Hints

Try on your own first. Reveal hints only when needed.

Hint 1: Getting Started

Recall the main pigment present inside leaf cells.

Hint 2: Key Approach

This pigment strongly absorbs red and blue parts of sunlight.

Hint 3: Almost There

Because it reflects green light, we see leaves as green.

Things to Consider

  • Sunlight is a mix of many colours.
  • Pigments absorb some colours, reflect others.
  • Reflected light decides the colour we see.
  • Chlorophyll is abundant in most leaves.

Concept Notes

Chlorophyll

Green pigment inside chloroplasts that drives photosynthesis and determines leaf colour.

Colour Perception

We see the wavelength that an object reflects, not the wavelengths it absorbs.

Important Rule:

Colour seen = light reflected by the object.

Leaf Gallery

Notice how leaves vary in shape, edge and size.

Broad

Broad Leaf

Large surface catches maximum sunlight, perfect for plants growing under taller trees.

Example: Mango
Needle

Needle Leaf

Slim needles cut wind and save water, helping plants in cold or dry zones.

Example: Pine
Heart

Heart-shaped Leaf

Pointed tip lets rain run off fast, preventing fungal growth in humid climates.

Example: Peepal
Fan

Fan Leaf

Segmented fan bends with wind, stopping leaves from tearing in coastal areas.

Example: Palm

Forest Finale

Where plants rule

Photo: Pixabay

Plant Kingdom’s Vast Reach

Step back for the big picture: one forest holds millions of plants, silently creating food, oxygen, and shelter—proof of nature’s enormous scale.

Learn more
Forests cover about one-third of Earth’s land surface.
Source: FAO