Life Processes in Plants Class 7 Notes Science Chapter 10

Plants are living things just like us. They:

• grow 🌿
• need food 🍽️
• respire (breathe) 🌬️
• transport water and food inside their body 💧🍃

But there is a big difference:
👉 Animals eat food
👉 Plants make their own food

In this chapter, we will learn how plants:

• grow
• make food (photosynthesis)
• transport water, minerals and food
• respire

1️⃣ How Do Plants Grow? 🌿

When a plant grows, you can see:

• 🌱 New leaves and branches
• 📏 Increase in height
• 🌳 Stem becomes thicker and stronger

For proper growth, plants need:

• 💧 Water (from soil)
• ☀️ Sunlight (from the Sun)
• 🧂 Nutrients / minerals (from soil)

Without these, plants cannot grow well.

2️⃣ Role of Sunlight and Water in Plant Growth ☀️💧

☀️ Sunlight

• Gives energy to the plant to prepare food
• Plants with enough sunlight look green, fresh and healthy
• If sunlight is less:
  • leaves may become pale or yellow 😞
  • food production decreases

💧 Water

• Helps in transporting nutrients inside the plant
• Keeps the plant firm and upright
• If a plant does not get water:
  • it wilts (leaves bend and hang down)
  • it may even die ❌

3️⃣ Ancient Indian Text – Vrikshayurveda 📜🇮🇳

In ancient India, people also studied plants.

• Vrikshayurveda is an old book on plant science 🌳
• It says: just planting a tree is not enough –
  👉 proper care, soil, water and manure are also required for good fruits and flowers

It includes ideas on:

• plant growth
• soil type
• farming practices

It also explains how to make organic manure using:

• water
• barley
• seeds like green gram, black gram, horse gram

This shows that Indians studied plants scientifically even long ago. 🧠

4️⃣ How Do Plants Get Food for Their Growth? 🥗

Animals eat food from outside.
Plants are special – they make their own food using:

• sunlight
• water
• carbon dioxide
• chlorophyll

This process is called photosynthesis 🌞🍃

Food made in plants is generally stored as starch. This starch:

• gives energy ⚡
• helps in growth and repair of plant parts

5️⃣ Leaves – Food Factories of Plants 🍃🏭

Leaves are called the “food factories” of plants because:

• They are broad and flat → can absorb more sunlight ☀️
• They have chlorophyll → green pigment that traps sunlight

• They get:
  • water + minerals from roots
  • carbon dioxide from air

Using all these, leaves prepare food for the whole plant. 🍽️

6️⃣ Starch Production and Iodine Test 🔬

The food prepared in leaves is stored as starch.

To check starch in a leaf, we do the iodine test:

1. Boil the leaf (to make it soft)
2. Remove its green colour (decolourise)
3. Add a few drops of iodine solution
4. If starch is present:
   • the leaf turns blue-black 🟦⚫

👉 The colour change shows that the leaf has prepared and stored food.

Decolourising helps us see this colour change clearly.

7️⃣ Effect of Sunlight and Leaf Colour 🌈🍁

Not all leaves look green:

• Some are red, violet, or brown 🍂
• They have other pigments that hide the green colour of chlorophyll
• But chlorophyll is still present inside

If you do an iodine test on such coloured leaves:

• You will see starch present if photosynthesis has occurred
• This means they also make food like normal green leaves

8️⃣ Chlorophyll and Food Preparation 💚

Leaves may have:

• green patches
• non-green patches

This is due to the presence or absence of chlorophyll.

• ✅ Green parts of the leaf:
  • contain chlorophyll
  • can make starch
• ❌ Non-green parts:
  • do not have enough chlorophyll
  • usually cannot make detectable starch

Also:

• Leaves kept in sunlight → produce starch
• Leaves kept in darkness → do not produce starch, even if they are green

👉 This proves:
Chlorophyll + Sunlight = Essential for preparing food (starch) in plants.

9️⃣ Role of Air in Food Preparation (Carbon Dioxide) 🌬️

Air contains carbon dioxide (CO₂), which is very important for photosynthesis.

• Plants take CO₂ from the air
• If a part of a leaf is kept away from CO₂, that part:
  • cannot make starch

So, no carbon dioxide = no food preparation in that part.

🌬️ Oxygen Release During Photosynthesis

While making food, plants also produce oxygen gas as a by-product.

• In an experiment with an aquatic plant in water:
  • plant kept in sunlight 🌞
  • tiny bubbles rise from its leaves
  • these bubbles are oxygen

👉 This shows that oxygen is released during photosynthesis, only in the presence of sunlight.

🔟 Photosynthesis 🌞🍃

Photosynthesis is the process by which plants prepare food using:

• 🌞 Sunlight
• 💧 Water
• 🌬️ Carbon dioxide
• 💚 Chlorophyll

The main food product is glucose (a simple sugar).

Glucose:

• gives immediate energy ⚡
• is often converted into starch for storage

🧮 Word Equation for Photosynthesis

Carbon dioxide + Water —(sunlight, chlorophyll)→ Glucose + Oxygen

• Glucose → used by plant
• Oxygen → released into the air (very important for animals and humans)

Photosynthesis happens mainly in leaves, but also in other green parts of the plant.

1️⃣1️⃣ About Rustom Hormusji Dastur 👨‍🔬🇮🇳

Many scientists around the world studied photosynthesis.

In India, Rustom Hormusji Dastur (1896–1961) was a famous plant scientist.

• He worked as Head of the Botany Department at:
  • Royal Institute of Science, Bombay (now Institute of Science, Mumbai)
• He studied how photosynthesis is affected by:
  • 💧 Water availability
  • 🌡️ Temperature
  • 🌈 Colour of light

His work helped us understand that these factors change the rate of photosynthesis.

1️⃣2️⃣ How Do Leaves Exchange Gases? (Stomata) 🍃🔍

Leaves have tiny pores on their surface called stomata.

Through stomata:

• 🌬️ Carbon dioxide enters the leaf (for photosynthesis)
• 🌬️ Oxygen goes out of the leaf (after photosynthesis)
• During respiration:
  • oxygen goes in
  • carbon dioxide comes out

Stomata can be:

• 👄 Open
• 🚫 Closed

depending on the plant’s needs (for gas exchange and to control water loss).

1️⃣3️⃣ Transport in Plants 🚚💧🍽️

Plants have a transport system to move:

• water
• minerals
• food

to all parts of the plant. This helps in:

• growth
• survival

🌱 Absorption of Water and Minerals

• Roots absorb water and minerals from the soil
• These move upwards to:
  • stems
  • branches
  • leaves

💧 Xylem – Transport of Water and Minerals

Xylem is a vascular tissue made of thin tubes.

• It carries water + dissolved minerals:
  • from 🌱 roots → to stems, branches and leaves
• We can see this by:
  • placing a plant twig in coloured water
  • after some time, colour appears in:
    • stem
    • leaves
    • sometimes petals
  • this shows coloured water moved through xylem

🍽️ Phloem – Transport of Food

Phloem is another vascular tissue.

• It carries food (glucose/starch) made in leaves to:
  • stems
  • roots
  • fruits
  • other growing parts
• Non-green parts like:
  • roots
  • developing fruits
  also need food → they receive it through phloem.
• Some of this food is stored in:
  • roots (e.g., carrot)
  • seeds (e.g., wheat)
  • fruits (e.g., mango)

1️⃣4️⃣ Do Plants Respire? 😮‍💨🌿

Yes! Plants also respire like animals.

• Respiration happens in all parts of the plant:
  • green parts
  • non-green parts

During respiration, plants:

• break down glucose using oxygen
• release:
  • carbon dioxide
  • water
  • energy ⚡

🧮 Word Equation for Respiration

Glucose + Oxygen → Carbon dioxide + Water + Energy

The energy released is used for:

• growth
• repair of cells
• transport of substances inside the plant

🌱 Experiment with Soaked Seeds

• Take soaked moong seeds and keep them in a flask
• They respire and give out carbon dioxide
• If you keep lime water in the setup:
  • it turns milky
  • this shows that CO₂ is present ✔️

👉 This proves that respiration happens in seeds and carbon dioxide is produced.

So plants have three main processes:

• 🌞 Photosynthesis – making food
• 🚚 Transport – moving water, minerals and food
• 😮‍💨 Respiration – using food to release energy

1️⃣5️⃣ Important Terms – Quick Revision 📝✨

Photosynthesis 🌞🍃

Process in which plants use sunlight, chlorophyll, carbon dioxide, and water to produce glucose and oxygen.

Chlorophyll 💚

Green pigment in leaves that captures sunlight for photosynthesis.

Stomata 🔍🍃

Tiny pores on the surface of leaves that allow gases to go in and out (CO₂, O₂).

Xylem 💧

Vascular tissue that transports water and minerals from roots to other parts of the plant.

Phloem 🍽️

Vascular tissue that transports prepared food (glucose or starch) from leaves to all parts of the plant.

Respiration 😮‍💨

Process by which plants break down glucose using oxygen to release energy, carbon dioxide, and water.

Glucose 🍬

Simple sugar made in photosynthesis; used for energy or converted to starch.

Starch 🍚

Storage form of carbohydrate in plants, made from glucose.