Class 6 Science Notes
Chapter 7 Getting to KNow Plants

Plants are living things (or living organisms) which grow in the soil and remain fixed at a place through their roots.

Plants do not take food like animals. They make their own food by photosynthesis.

Most of the plants have green leaves. A few plants have reddish leaves.

Most of the plants bear flowers. They are called flowering plants.

Examples of flowering plants are: Rose, Mango, Neem, Bougainvillea, Mustard, Sunflower plant, Grass, Lemon, Wheat, Maize, Chilli, Tomato, Tulsi, Peepal, Banyan, Banana, Sugarcane and Potato.

Some of the plants, however, do not bear flowers. They are called non-flowering plants (or flowerless plants).

Examples of nonflowering plants are: Ferns, Moss, Algae, Fungi (like Mushroom), and Conifers (like Pine trees).

Classification of Plants

1. Herbs

Herbs are small plants having a soft and delicate stem.

Herbs do not have woody stem. They are non-woody plants.

Herbs have a green and tender stem.

Herbs usually do not grow more than one metre in height.

Herbs have a short life-span. They may live for only one or two seasons.

Some of the examples of herbs are: Tomato, Mustard, Radish, Sunflower, Wheat, Paddy (Rice), Cabbage, Carrot, Ginger and Turnip.

2. Shrubs

Shrubs are medium-sized plants with a hard and woody stem, branching out near the base.

The shrubs are bigger than herbs but smaller than trees.

The life-span of shrubs is for many years but it is less than that of trees.

Though the stem of a shrub is hard but it is not very thick.

Shrubs do not have a distinct main stem or trunk.

Shrubs tend to branch near ground level, so many branches are seen rising just above the ground (giving them a bushy appearance).

Some of the examples of shrubs are: Rose, Jasmine (Chameli), Croton, Tulsi, Bougainvillea, China rose (Shoe flower), Pomegranate, Henna (Mehndi), and Lemon.

3. Trees

Trees are tall and big plants with hard and thick woody stem.

The trees have one main stem called 'trunk' which usually gives out branches and leaves.

The branches in a tree appear higher up on the stem (much above the ground).

Palm trees are never branched.

The coconut tree is a type of palm tree. The trees are very big in size.

The life-span of trees is very large. Trees usually live for many-many years.

Some of the examples of trees are: Neem, Mango, Palm, Teak, Oak, Sandalwood, Coconut, Eucalyptus, Banyan (Bargad) and Jamun.

Differences between Shrubs and Trees

Shrubs and trees are both woody plants.

The main differences between shrubs and trees are the following:

(i) Shrubs are medium-sized plants whereas trees are very tall and big plants.

(ii) Shrubs branch near the ground whereas trees branch much above the ground.

(iii) Shrubs have thin stem whereas trees have thick stem.

Other Plants

1. Climbers

A plant having thin, long and weak stem which cannot stand upright but readily climbs up a neighbouring support (like a fence) or a tree is called a climber (or climber plant).

A climber plant has special organs for climbing called 'tendrils' (some climber plants have stem tendrils whereas others have leaf tendrils).

The tendrils of climber plants wind themselves around any neighbouring object and help the plant to climb up.

2. Creepers

A plant having thin, long and weak stem which cannot stand upright and spreads on the ground, is called a creeper.

A creeper plant has no climbing organs like tendrils (which are present in climber plants).

A creeper grows along the ground or other surfaces by extending long shoots (or branches).

The two important creepers are:  Strawberry plant and Money plant.

If a creeper plant is to be grown like a climber plant, then the top end of its stem has to be tied with a string and the other end of string fixed at a height.

For example, a money plant can be made to grow up by tying a string to its top end.

Main difference between the climber plants and creeper plants is that climber plants have climbing organs like tendrils (on their stems or leaves) but creeper plants have no such climbing organs.

Parts of a Plant

1. Root

That part of a plant which is below the ground (in the soil), is called root.

The main functions of the roots of a plant are as follows:

(i) Roots anchor the plant to the soil. It means that roots fix the plant firmly to the soil (or ground). This prevents the plant from being pulled out easily or blown away by the wind.

(ii) Roots absorb water and minerals from the soil. These are needed for the manufacture of food by plant leaves.

(iii) Roots help in holding the soil together. In this way, roots prevent the soil from being blown away by wind or washed away by water, and help in the conservation of soil.

The soil contains water. The minerals present in soil get dissolved in this water. The roots absorb water and minerals from the soil and the stem carries them to the leaves and other parts of the plant. The leaves prepare food.

The food prepared in leaves is carried by the stem to all the parts of the plant, including roots.

Some of the plants store food in their roots. We eat such roots as food, e.g., carrot, radish, sweet potato, turnip and tapioca.

Types of Roots

(i) Tap Roots

Tap root is a straight tapering root which grows vertically down into the soil and gives out branches in all the sides.

Tap root is the main root and the smaller, side roots are called lateral roots. Tap root is quite thick but its branches (lateral roots) are much thinner.

Some of the plants having tap roots are: Pea plant, Neem tree, Mango tree, Marigold, Tulsi, Gram, Carrot, Radish, Beet, and Turnip.

(ii) Fibrous Roots

Some plants do not have a main root. They have a bunch of smaller roots called fibrous roots.

The fibrous roots consist of many thin, fibre-like roots of a similar size.

The fibrous roots spread out in the soil and give a firm support to the plant.

Some of the plants having fibrous roots are: Wheat, Paddy (Rice), Grass, Maize, Millet (Bajra), Bamboo, Sugarcane and Sweet potato.

2. Stem

The part of a plant which rises vertically up from the ground is called its stem.

The stem of a plant is the link between the roots and the rest of the plant.

The stem of a tree is the strongest part of the tree and it is known as trunk.

Most of the tree trunks are covered with a tough layer called 'bark’.

Bark protects the inner parts of a tree.

The stem of a plant has a large number of narrow tubes inside it.

One type of tubes (Xylem) in the stem carry water and dissolved minerals from the roots to the leaves and other parts.

Another type of tubes (Phloem), present in the stem carry the food from the leaves to all other parts of the plant, including roots.

Main functions of the stem of a plant

(i) The stem holds the plant upright (or erect).

(ii) The stem of a plant carries water and minerals from the roots to the leaves and other parts of the plant.

(iii) The stem carries the prepared food from the leaves to other parts of the plant.

(iv) The stem holds the leaves in such a way that the leaves are able to get plenty of sunlight for preparing food by photosynthesis.

Activity – Stem of a plant carries water to the leaves and flowers

  • We cut a small branch of a plant having flowers with white petals (This branch of the plant is a kind of stem).
  • Place this branch vertically in a vessel containing red ink and water solution.
  • Allow the branch to stand in this coloured water for a few hours. We will see red coloured lines in the leaves.
  • We will also see that the white petals of the flower have turned red.
  • This experiment shows that the stem (or branch) of the plant carries red-coloured water upwards to the leaves and flowers.
  • Just like red ink, the minerals dissolved in water also move up the stem alongwith water.

3. Leaf

The leaf is a thin, broad, flat and green part of a plant which is attached to the stem (or branch).

A leaf consists mainly of two parts: lamina and petiole.

Lamina is commonly known as leaf blade (broad, green part) and petiole is commonly known as leaf stalk.

The thin stalk with which leaf is attached to the stem (or branch) is called 'petiole'.

There is a mid-rib (main vein) in the centre of lamina (or leaf blade).

A large number of veins spread out from the mid-rib to all the parts of the leaf.

The mid-rib and veins consist of bundles of tiny tubes some of which carry water (and dissolved minerals) into the leaf, and others carry away the food from the leaf.

There are minute pores on the surface of a leaf (which are called stomata).

Stomata are very small. We cannot see them with naked eyes.

The stomata allow the gases to move in and out of the leaf.

They also allow excess water vapour to go out of the leaf.

The leaves of plants contain a green coloured pigment called 'chlorophyll’.

Chlorophyll imparts green colour to the leaves.

Chlorophyll can absorb (or trap) energy from sunlight.

Three main functions of leaves

(i) The leaves make food for the plant (by photosynthesis).

(ii) The leaves get rid of excess water from the plant (through transpiration).

(iii) The leaves carry out the process of respiration in plants (which is the production of energy from food).

The leaves are food factories.

In photosynthesis, the green leaves of plant combine carbon dioxide and water in the presence of sunlight to make food and oxygen gas. 

Carbon dioxide   +   Water   →Chlorophyll  Sunlight     Food   +   Oxygen

The term 'photosynthesis' means 'making things with light'.

Carbon dioxide gas needed for making food is taken by the leaves from air and water is carried into leaves from the soil through the stem.

Sunlight provides the energy for making food.

Chlorophyll present in the green leaves helps in trapping energy from sunlight (so that it can be utilised in making food).

Oxygen gas is produced in the leaves during photosynthesis. This oxygen goes into air.

Photosynthesis

The simplest food prepared by the leaves by photosynthesis is glucose.

Some of the glucose is converted into starch. This starch is stored as food in various parts of the plant (including leaves).

Transpiration

A plant keeps on absorbing water from the soil all the time through its roots. Due to this, a lot of water gets collected in the body of the plant.

Some of this water is used up by the plant in making food.

The extra water present in the body of plant is given out constantly as water vapour through the tiny pores (stomata) of the leaves.

The evaporation of water from the leaves of plants is called transpiration.

During transpiration, the excess water present in the plant is lost into the air as water vapour.

This water vapour in air helps in bringing rain.

Activity: To Show That Leaves Make Food by Photosynthesis

  • Pluck a green leaf from a potted plant which has been kept in sunlight.
  • Put the green leaf in a small beaker and cover it completely by adding alcohol (or spirit).
  • Place the beaker containing leaf and alcohol in a bigger beaker containing water.

  • Take out the decolourised leaf from alcohol and wash it thoroughly with water to remove any chlorophyll that may be sticking to it.
  • Place the decolourised leaf in a petri-dish. Pour dilute iodine solution over the decolourised leaf with the help of a dropper. The leaf turns blue-black showing the presence of starch in it. This starch is the food which has been prepared by the leaf by photosynthesis.

Heating Instructions/Precautions:

Heat the water in bigger beaker over a burner.

The hot water will then heat alcohol in smaller beaker.

The hot alcohol removes the green colour (chlorophyll) from the leaf.

Keep heating till all the green colour of leaf is removed. The leaf becomes almost colourless and the alcohol becomes green.

It is necessary to remove green chlorophyll from the leaf because it interferes with the test for starch.

Activity: To Show That Sunlight is Necessary for Photosynthesis

  • Take a potted plant having green leaves and place it in a completely dark place for 2 to 3 days to de-starch its leaves.
  • Take a thin strip of aluminium foil and wrap it in the centre (middle part only) of one leaf on both the sides, while the leaf is still attached to the plant. The remaining part of leaf remains uncovered so that it is exposed to sunlight.

  • Keep the potted plant in bright sunshine for 3 to 4 days.
  • Pluck the partially covered leaf from the plant and remove the aluminium foil.
  • Remove chlorophyll from this leaf by heating in alcohol. The leaf becomes colourless. Wash it with water.
  • Place the decolourised leaf in a petri-dish. Pour dilute iodine solution over the decolourised leaf with the help of a dropper.

(a) The middle part of leaf, which was covered with aluminium foil, does not turn blue-black on adding iodine solution, showing that no starch is present in the middle part of the leaf. This means that the middle part of leaf which did not get sunlight, could not make starch food by photosynthesis.

(b) The uncovered parts of leaf which were exposed to sunlight, turn blue-black on adding iodine solution, showing that starch is present in the outer parts of leaf. This means that the outer parts of leaf which got sunlight, could make starch food by photosynthesis.

Activity: To Show Transpiration in Plants

  • Take a well-watered potted plant having big leaves.
  • Enclose a leafy stem (or branch) of the plant in a clean polythene bag and seal the mouth of polythene bag properly with cello tape.
  • Keep this potted plant in the sunshine for 2 to 3 hours. We will see a number of water droplets on the inner side of the polythene bag. 


The leaves of plant give out water vapour.

Some of this water vapour condenses (liquefies) to form tiny drops of water. It is these droplets of water which we see sticking to the inner sides of the polythene bag.

This activity shows that the leaves of a plant lose water through transpiration.

Venation

All the leaves contain veins. The arrangement of veins in the lamina (or leaf blade) is known as venation of the leaf.

There are two main types of venation (or vein arrangements) in the leaves. These are:

(i) Reticulate venation

In reticulate venation, the veins in a leaf occur in an irregular way forming a net-like design. The term 'reticulate' means 'resembling a net or network'.

The examples of plants having reticulate venation in their leaves are: Pea plant, Neem tree, Mango tree, Marigold, Tulsi, Mustard, Sunflower, Orange, Guava, Pulses, Tamarind (Imli), Rose, China Rose, Coriander (Dhania), and Peepal.

(ii) Parallel venation

In parallel venation, the veins in a leaf run parallel to one another on both the sides of the mid-rib.

The examples of plants having parallel venation in their leaves are: Wheat, Paddy (Rice), Maize, Millet (Bajra), Sugarcane, Bamboo, Barley, Lily and Banana.

Activity: Taking an Impression of a Leaf

  • Put a dry leaf of a tree having prominent veins under a white sheet of paper kept on a table.
  • Hold the pencil in your hand with its tip sideways and rub it on that part of paper which has leaf below it.
  • We will get an impression of the leaf on paper having some dark lines on it. These lines show the veins of the leaf.

Relationship Between Venation and Type of Roots

  • The plants having leaves with reticulate venation have tap roots.
  • (ii) The plants having leaves with parallel venation have fibrous roots.

For example:

(a) The sunflower plant has reticulate venation in its leaves, so it will have tap root.

(b) The wheat plant has parallel venation in its leaves, so it will have fibrous roots.

4. Flowers

The flower is that part of a plant which contains the reproductive organs. The main function of flowers is to produce fruits and seeds.

Some of the common flowers are: Rose, Bougainvillea, Jasmine, Lily, Sunflower and Marigold.

Parts of a Flower

The main parts of a flower are: Sepals, Petals, Stamen and Pistil.

(i) The green, leaf-like parts in the outermost circle of a flower are called sepals. The sepals protect the flower when it is in the form of a bud in the initial stage. Sepals may either be separate from one another or joined together.

(ii) Inside the sepals are the petals of a flower. Petals of flowers can be of different colours, shapes and sizes. The petals can be red, blue, green, orange, pink, white, or any other colour. The petals of some of the flowers have natural scents in them due to which they smell very nice. Petals also attract insects.

The ring of colourful petals in a flower protects the reproductive organs (stamen and pistil) of the flower.

Petals may be either separate from one another or joined together to form a tubular flower.

In many flowers, the number of petals is equal to the number of sepals in it. For example, the buttercup flower has 5 green sepals and an equal number of 5 petals.

In some flowers, however, the number of petals is not equal to the number of sepals. In such flowers, the number of petals is much more than the number of sepals. For example, the rose flower has 5 green sepals but the number of petals is much more than five. Thus, the number of petals and sepals in a flower is not always equal.

(iii) Just inside the petals of a flower, there are many little stalks with swollen tops. These stalks with swollen tops are called stamens. The stamen is the male part of a flower.

The stamen is actually made up of two parts: a filament and an anther. The stalk of stamen is called filament and the swollen top of stamen is called anther. The anther contains a yellow powder-like substance called pollen (or pollen grains). If we cut the anther of a flower horizontally with a blade, we can see the pollen grains in it. The pollen grains contain male sex cells of a plant. There are many stamens in a flower. They form a ring around the female part of the flower called pistil.

(iv) In the centre of a flower, there is a flask-shaped organ. This flask-shaped organ of a flower is called pistil.

The pistil is the female part of a flower. A pistil is made up of three parts: stigma, style and ovary. The top part of a pistil is called stigma. Stigma is very sticky so that pollens can stick to it. The middle part of a pistil is called style. It is a tube which connects stigma to ovary. The swollen part at the bottom of the pistil is called ovary. The ovary contains tiny, egg-like structures called ovules.

If we cut the ovary of a flower vertically with a blade and observe with a magnifying lens, we will see tiny egg-like structures inside the ovary.

These tiny, egg-like structures are ovules. The ovary may contain one or several ovules. The ovules contain female sex cells of a plant. The female organ 'pistil' is surrounded by a number of male organs called 'stamens'. Pistil is also known as Carpel. In most plants, the stamens and pistils (male and female parts) are present in the same flower. In some plants, however, stamens and pistils are present in separate flowers.

5. Fruits and Seeds

A fruit is that part of a plant which contains the seeds. Apples, oranges, plums, lemons, and tomatoes, are all fruits. They all have seeds inside them. The pea pod is also a fruit. The peas inside it are seeds.

Formation of Fruits and Seeds

The fruits and seeds are formed from flowers by the process of pollination and fertilisation. The transfer of pollen grains from anther of a stamen to the stigma of a pistil is called pollination. Pollination is done by insects, wind and water. In other words, the pollen grains are carried from the anther of a stamen to the stigma of a pistil by insects (like bees), blowing wind, and falling water.

When the pollen grains fall on stigma, they move down through the tube called style and reach the ovary. In the ovary, the male sex cells present in pollens join with the female sex cells present in ovules. The joining together of male and female sex cells is called fertilisation. After fertilisation, the ovules grow and become seeds. The ovary of flower grows and becomes a fruit (with seeds inside it). A fruit protects the seeds. The other parts of the flower dry up and fall off.

The wheat grains, gram (chana), corn (makka), peas, pulses, and beans, which we use as food are all seeds of their respective plants. All these seeds can germinate under suitable conditions to produce new plants. For example, when we sow wheat seeds in the fields, they grow to give new wheat plants (or wheat crop).


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