nUTRITION iN pLANTS

All animals depend on plants! Herbivores (like cows) eat plants directly. Carnivores (like lions) eat the animals that ate the plants. So, plants are the ultimate source of food for everyone!

How Do Plants Make Food? (Photosynthesis)

Plants make their food mainly in their green leaves. Therefore, leaves are famously called the "Food Factories" of plants.

The 4 Raw Materials Needed:

Raw Material Where does the plant get it? (Source)

Water From the Soil (absorbed by roots)

Minerals From the Soil (absorbed along with water)

Carbon dioxide From the Air

Sunlight From the Sun

Why are leaves green?

Leaves contain a special green pigment called Chlorophyll. Think of chlorophyll as a tiny solar panel—it helps the leaf trap sunlight energy so it can cook its food!

One-Line Question & Answers

Q1. What are nutrients?

Ans: Essential substances in food that our body needs for growth, health, and energy.

Q2. Why are plants called autotrophs?

Ans: Because they can prepare their own food from simple natural materials.

Q3. What is photosynthesis?

Ans: The process by which green plants prepare their own food using sunlight.

Q4. What is chlorophyll?

Ans: The green pigment found in leaves that traps sunlight.

Q5. Why are animals called heterotrophs?

Ans: Because they cannot make their own food and must depend on plants or other animals.

The Building Blocks of Life: Cells

Just like a school or building is made of individual bricks, the bodies of all living organisms are made of tiny units called cells.

Cells are so incredibly small that you can only see them under a microscope. Some tiny organisms are made of just a single cell!

The 3 Main Parts of a Cell:

Cell Membrane: A thin outer boundary that encloses and protects the cell.
Nucleus: A round structure right in the center that acts as the "brain" or control room of the cell.
Cytoplasm: A clear, jelly-like substance that fills up the space around the nucleus.

Inside the "Food Factory" (How Photosynthesis Works)

Let's look closely at how a leaf actually makes food and answers Boojho and Paheli's big questions.

How does Air get inside?

On the surface of leaves, there are tiny, invisible pores (holes) called stomata.

Air enters the leaf through these stomata.
Each stoma is guarded by two special guard cells that control when the pore opens and closes.

How do Water and Minerals reach the leaves?

Boojho's Question: "How does water from the roots travel all the way up to the top leaves?"

Answer: Inside the plant, there are long, narrow tubes called vessels. They act just like water pipes running throughout the roots, stem, branches, and leaves to form a continuous pipeline.

The Photosynthesis Equation

During the day, cells containing chlorophyll use sunlight to combine carbon dioxide and water to make food. The chemical process looks like this:

What happens to the food? The carbohydrate food is stored in the leaves as starch.
The Oxygen Release: Plants release oxygen gas into the air during this process—which is exactly what humans and animals breathe to stay alive!

Special Cases in Nature

A. Desert Plants (Cactus)

To prevent water loss in hot deserts through transpiration (evaporation), desert plants don't have regular leaves. Instead, their leaves are modified into sharp spines.

Where is food made? They use their thick green stems to carry out photosynthesis!

B. Colorful Leaves (Red, Violet, or Brown)

Boojho's Question: "Do plants with deep red, violet, or brown leaves also perform photosynthesis?"

Answer: Yes, they do! These leaves still contain green chlorophyll. However, a large amount of red or brown pigment masks (hides) the green color.

C. Algae (The Green Slimy Patches)

Have you ever seen slimy, green patches floating in a pond or stagnant well water in Goa? These are living organisms called algae.

They look green because they contain chlorophyll.
Because they have chlorophyll, algae can also make their own food using photosynthesis.

Revision Questions

Q1. What are the tiny pores on the surface of leaves called?

Ans: Stomata.

Q2. Name the jelly-like substance found inside a cell.

Ans: Cytoplasm.

Q3. Why is the Sun called the ultimate source of energy?

Ans: Because plants use solar energy to make food, and all animals depend on plants to survive. Without the sun, life on Earth would stop.

Q4. What is the storage form of food in a leaf?

Ans: Starch (which is a form of carbohydrate).

Q5. How do we test for the presence of starch in a leaf?

Ans: By performing an Iodine Test (a blue-black color indicates starch is present).

Making Food Other Than Carbohydrates

Through photosynthesis, plants make carbohydrates (which contain Carbon, Hydrogen, and Oxygen). But plants also need to build proteins and fats to grow properly.

Proteins are nitrogenous substances, which means they absolutely require Nitrogen to be made.

The Nitrogen Dilemma

The Problem: The air is full of Nitrogen gas (~78%), but plants cannot absorb it directly through their leaves like carbon dioxide.
The Solution:
1. Soil Bacteria: Useful bacteria in the soil convert gaseous nitrogen into a soluble (liquid) form that roots can absorb easily.
2. Fertilisers: Farmers regularly add nitrogen-rich fertilisers to fields to help crops grow better.

Other Modes of Nutrition (When Plants Can't Make Food!)

Some plants do not have chlorophyll. Since they cannot perform photosynthesis, they act like heterotrophs and rely on other living plants for food.

A. Parasitic Plants (The Stealers)

Have you ever seen yellowish, thread-like structures tangling around big trees in Goa? That is Cuscuta (also known as Amarbel).

The Host: The green tree that provides the food.
The Parasite: The plant (like Cuscuta) that steals nutrients from the host. Because it deprives the host tree of precious nutrition, it is called a parasite.

Paheli's Thought: Are mosquitoes, bed bugs, lice, and leeches also parasites?

Answer: Yes! They attach themselves to a host (like humans or animals) and suck blood to steal nutrients without giving anything back.

B. Insectivorous Plants (The Hunters)

Some plants actually trap and eat insects! They are called insectivorous plants. A famous example is the Pitcher Plant.

How the Pitcher Plant Traps Insects:

The Modification: The leaf of the plant turns into a deep pitcher-like jug structure with a flap-like lid at the top.
The Trap: Inside the pitcher, there are tiny hairs pointing downwards.
The Catch: When an insect lands inside, the lid snaps shut automatically. The insect slips down and gets tangled in the sticky hairs.
The Digestion: The plant secretes special digestive juices inside the jug to dissolve and digest the insect.

Why do they eat insects if they are green?

These plants usually grow in marshy, swampy soils that are very poor in nitrogen nutrients. To fulfill their nitrogen requirements, they hunt insects!

Revision Questions

Q1. Name a plant that lacks chlorophyll and lives as a parasite.

Ans: Cuscuta (Amarbel).

Q2. Why do plants need nitrogen?

Ans: Nitrogen is essential to make proteins, which help the plant grow.

Q3. How do roots absorb nitrogen from the soil?

Ans: They absorb soluble forms of nitrogen released by soil bacteria, or from artificial fertilisers added by farmers.

Q4. Why does a pitcher plant eat insects even though it has green leaves?

Ans: It grows in nutrient-poor soil that lacks nitrogen. It traps insects to fulfill its nitrogen requirement.

Q5. What prevents a trapped insect from climbing out of a pitcher plant?

Ans: The downward-pointing hairs inside the pitcher entangle the insect and prevent it from moving up.

Saprotrophs (The Decay Eaters)

Have you ever seen white packets of mushrooms in markets, or fluffy, tiny umbrellas growing on damp wood during the Goan monsoon? These belong to a group of organisms called Fungi.

Fungi do not have mouths to eat, and they lack chlorophyll, so they cannot perform photosynthesis. Instead, they use a completely different style of eating called Saprotrophic Nutrition.

How Fungi Feed:

They grow on dead and decaying matter (like rotten wood, stale bread, old pickles, or wet leather).
They secrete (release) digestive juices directly onto the dead matter.
These juices turn the solid matter into a liquid solution.
The fungi then absorb the nutrients from this solution.

Definition: The mode of nutrition in which organisms take in nutrients in liquid form from dead and decaying matter is called Saprotrophic Nutrition. Organisms that use this are called Saprotrophs.

The Monsoon Mystery: Why do Fungi appear suddenly?

Tiny, invisible fungal spores are always floating around in the air.
During hot and humid seasons (especially the rainy season), these spores land on wet, warm things.
Once they find moisture and warmth, they germinate (wake up) and start growing rapidly, spoiling clothes, shoes, and food.

Is Fungi Good or Bad?

The Good: Mushrooms are delicious to eat; Yeast helps make bread and local Goan pao fluffy; some are used to make medicines (antibiotics).
The Bad: Some fungi cause diseases in crops (destroying fields) as well as skin infections in humans.

Symbiotic Relationships (The Partnership Mode)

Sometimes, two completely different organisms live together and share both their shelter and their nutrients. This friendly teamwork is called a Symbiotic Relationship.

Example 1: Trees and Fungi

Certain fungi live inside the roots of trees.

The tree provides ready-made food nutrients to the fungus.
In return, the fungus helps the tree's roots absorb water and minerals from the hard soil much faster.

Example 2: Lichens (Alga + Fungus)

Lichens are beautiful, crusty patches you see growing on tree bark or old rocks. They are actually a two-member team living together:

As a Fungus - Cannot make food. Provides: Shelter, water, and minerals to the Alga.

As an Alga - Contains chlorophyll and can do photosynthesis. Provides: Ready-made food to the Fungus.

How Nutrients are Put Back into the Soil

As plants grow, they constantly absorb mineral nutrients like Nitrogen ($N$), Phosphorus ($P$), and Potassium ($K$) from the ground. Over time, the soil runs out of these vital nutrients.

Farmers refill the soil using two major methods:

Method A: Manures and Fertilisers

Farmers and gardeners regularly add chemical fertilisers or natural cow dung manure to enrich the soil and keep plants healthy.

Method B: Nature's Secret Weapon—Rhizobium Bacteria

Crops need a massive amount of Nitrogen to produce proteins. After harvest, the soil is left empty of nitrogen.

To fix this naturally, nature uses a brilliant symbiotic relationship:

The Bacteria (Rhizobium): This tiny bacterium lives inside the root nodules of leguminous plants (pulses/dals like gram, peas, and moong). It takes nitrogen gas from the air and converts it into a liquid, soluble form that the plant can drink.
The Plant: Since Rhizobium cannot make its own food, the plant provides it with free food and a safe shelter in its roots.

Farmer's Benefit: Thanks to this partnership, farmers do not need to buy expensive chemical nitrogen fertilisers for fields where they grow pulses!

Boojho's Final Thought: Are Pitcher Plants Partial Heterotrophs?

Yes! Since a pitcher plant is green, it does photosynthesis to make carbohydrates (acting as an autotroph). But because it hunts bugs to get its missing nitrogen, it also acts as a heterotroph. Therefore, insectivorous plants are called Partial Heterotrophs.

Revision Questions

Q1. What is a symbiotic relationship?

Ans: A relationship where two different organisms live together to share shelter and nutrients for mutual benefit.

Q2. Name the two partners that make up a Lichen.

Ans: An Alga (provides food) and a Fungus (provides shelter and water).

Q3. Why do fungal spores grow rapidly during the rainy season?

Ans: Because the monsoon provides the exact hot, wet, and humid conditions required for the spores to germinate.

Q4. Which bacterium helps in converting atmospheric nitrogen into a usable form for plants?

Ans: Rhizobium bacteria.

Q5. Why do farmers love leguminous (pulse) crops?

Ans: Because the Rhizobium bacteria in their roots automatically enrich the soil with nitrogen, saving the farmer money on fertilisers.

Chapter 1: Exam Practice Worksheet

SECTION A: Objective & Very Short Type (1 Mark Each)

Q1. Fill in the blank:

The tiny pores on the surface of leaves through which carbon dioxide enters are called ___________.

Answer: Stomata

Q2. Multiple Choice Question:

Which of the following is a parasitic plant?

(a) Pitcher plant

(b) Cuscuta (Amarbel)

(d) Lichen

Answer: (b) Cuscuta (Amarbel)

Q3. One-Word Answer:

Name the structural building blocks that make up the bodies of all living organisms.

Answer: Cells

Q4. State True or False:

The solar energy trapped by leaves is stored in the plant in the form of starch.

Answer: True

SECTION B: Short Answer Type I (2 Marks Each)

Q5. Differentiate between Autotrophs and Heterotrophs with one example of each.

Answer:

Autotrophs: Organisms that prepare their own food from simple natural substances. Example: Green plants.
Heterotrophs: Organisms that cannot make their own food and depend on plants or other animals for nutrition. Example: Humans / Lions.

Q6. Give Scientific Reason:

Why do farmers regularly grow leguminous crops (like moong beans or pulses) between major harvests?

Answer: Leguminous plants have Rhizobium bacteria in their root nodules. These bacteria fix atmospheric nitrogen into a soluble form for the plant. When grown, they naturally enrich the soil with nitrogen, saving the farmer the cost of buying chemical fertilisers.

Q7. Explain how Saprotrophs like fungi take in nutrients since they do not have mouths to eat.

Answer: Fungi secrete digestive juices directly onto dead and decaying matter. This converts the decaying matter into a liquid solution. They then absorb the necessary nutrients from this solution.

SECTION C: Short Answer Type II (3 Marks Each)

Q8. Answer the following questions regarding insectivorous plants:

(a) Name one insect-eating plant.
(b) How does the leaf of this plant change to trap insects?
(c) Why do these plants eat insects even though they are green?

Answer:

(a) Pitcher Plant.
(b) The leaf modifies into a deep, hollow jug-like pitcher with a lid at the top that can open and close.
(c) They grow in marshy soils that completely lack nitrogen. They eat insects to fulfill their nitrogen requirements.

SECTION D: Long Answer Type (4 Marks)

Q9. Explain the process of Photosynthesis.

(a) Write down the complete word equation for photosynthesis. (2 Marks)
(b) Name the four essential raw materials required for this process. (2 Marks)

Answer:

(a)

(b) The four essential raw materials are: Sunlight, Chlorophyll, Water & Minerals (from soil), and Carbon Dioxide (from air).

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