CLASS VII – SCIENCE

CHAPTER -1
NUTRITION IN PLANTS
 WHY DO WE NEED FOOD?
The food enable living
organisms to:

• build their bodies,

• to grow,
• to repair damaged parts
of their bodies and
• provide the energy to
carry out life processes
 NUTRIENTS

Definition:

Carbohydrates, proteins, fats, vitamins and

minerals are components of food. These
components of food are necessary for our
body and are called nutrients.
 NUTRITION

Definition:

Nutrition is the mode of taking food by an

organism and its utilization by the body.
DIFFERENT MODES OF NUTRITION
MODES OF
NUTRITION

AUTOTROPH HETEROTROPH

SYMBIOTIC
SAPROTROPHS
RELATIONSHIP

INSECTIVOROUS
PARASITE
PLANTS
 AUTOTROPES

The mode of nutrition in

which organisms make food
themselves from simple
substances is called
autotrophic (auto = self;
trophos = nourishment)
nutrition. Therefore, plants
are called autotrophs.

GREEN PLANTS
 HETEROTROPES

Animals and most

other organisms
take in ready made
food prepared by
the plants. They are
called heterotrophs
(heteros = other).
ANIMALS
 SAPROTROPH
The mode of nutrition in which organisms take in
nutrients in solution form from dead and decaying matter
is called saprotrophic nutrition. Plants which use
saprotrophic mode of nutrition are called saprotrophs.
 PARASITES
• There are some plants which do not have
chlorophyll.
• They cannot synthesis their food.
• such plants depend on the food produced by
other plants.
• They use the heterotrophic mode of nutrition.
• It does not have chlorophyll in it.
• It takes ready made food from the plant which it
is climbing.
• The plant on which it climbs is called a host. CUSCUTA
• Since it deprives the host of valuable nutrients, it
is called a parasite.
 INSECTIVOROUS PLANTS

• There are a few plants which can trap insects and digest
them.
• Such insect-eating plants are called insectivorous plants.
• Such plants do not get all the required nutrients from the
soil in which they grow.
SOME INSECTIVOROUS PLANTS

PITCHER PLANT VENUS FLY TRAP SUN DEW

 SYMBIOTIC RELATIONSHIP
• Some organisms live together and share shelter and nutrients. This is called symbiotic
relationship.
• For example, certain fungi live in the roots of trees. The tree provides nutrients to the fungus
and, in return, receives help from it to take up water and nutrients from the soil.
• This association is very important for the tree. In organisms called lichens, a chlorophyll-
containing partner, which is an alga, and a fungus live together.
• The fungus provides shelter, water and minerals to the alga and, in return, the alga provides
food which it prepares by photosynthesis.
 SYMBIOTIC RELATIONSHIP
• Usually crops require a lot of nitrogen to make proteins. After the harvest, the soil becomes
deficient in nitrogen. Though nitrogen gas is available in plenty in the air, plants cannot use it
in the manner they can use carbon dioxide.
• They need nitrogen in a soluble form. The bacterium called Rhizobium can take atmospheric
nitrogen and convert it into a soluble form. But Rhizobium cannot make its own food. So it
lives in the roots of gram, peas, moong beans and other legumes and provides them with
nitrogen. Most of the pulses (dals) are obtained from leguminous plants.
• In return, the plants provide food and shelter to the bacteria. They have a symbiotic
relationship. This association is of great significance for the farmers.
 CELL STRUCTURE
• Buildings are made of bricks. Similarly, the
bodies of living organisms are made of tiny
units called cells.
• Cells can be seen only under the microscope.
• Some organisms are made of only one cell.
• The cell is enclosed by a thin outer boundary,
called the cell membrane.
• Most cells have a distinct, centrally located
spherical structure called the nucleus.
• The nucleus is surrounded by a jelly-like
substance called cytoplasm.
 PHOTOSYNTHESIS
1. STOMATA

• Carbon dioxide from air is taken in

through the tiny pores present on the
surface of the leaves.
• These pores are surrounded by ‘guard
cells’. Such pores are called stomata.
• Water and minerals are transported to the
leaves by the vessels which run like pipes
throughout the root, the stem, the
branches and the leaves.
• They form a continuous path or passage
for the nutrients to reach the leaf.
 2.CHLOROPHYLL PIGMENT
• The leaves have a green pigment called chlorophyll.
• It helps leaves to capture the energy of the sunlight.
• This energy is used to synthesize (prepare) food from carbon dioxide and
water.
• Since the synthesis of food occurs in the presence of sunlight, it is called
photosynthesis (Photo: light; synthesis : to combine).
• Chlorophyll, sunlight, carbon dioxide and water are necessary to carry
out the process of photosynthesis.
• It is a unique process on the earth.
• The solar energy is captured by the leaves and stored in the plant in the
form of food.
• Thus, sun is the ultimate source of energy for all living organisms
DIAGRAM SHOWING PHOTOSYNTHESIS
 EQUATION FOR PHOTOSYNTHESIS:
• During photosynthesis, chlorophyll containing cells of leaves in the
presence of sunlight, use carbon dioxide and water to synthesise
carbohydrates .
• The process can be represented as an equation:

Carbon dioxide + water (in the presence of sun light and

chlorophyll pigment) Carbohydrate oxygen

CO2+H2O SUNLIGHT C6H12O6+O2+H2O

CHLOROPHYLL
 LEAFS OF VARIOUS COLOURS.

The leaves other than green also have

chlorophyll. The large amount of red,
brown and other pigments mask the
green colour Photosynthesis takes
place in these leaves also.
 ALGAE DO PHOTOSYNTHESIS.

Slimy, green patches in ponds

or in other stagnant water
bodies. These are generally
formed by the growth of
organisms called algae. They
contain chlorophyll which
gives them the green colour.
Algae can also prepare their
own food by photosynthesis.
 HOW NUTRIENTS ARE
REPLENISHED IN THE SOIL
 Spreading manure or fertilizers in the fields,
( Fertilizers and manures contain plant nutrients such as nitrogen,
potassium, phosphorous, etc. )These nutrients need to be added from time to time
to enrich the soil.
 Growing leguminous plant,
(that can fix atmospheric nitrogen with the help of rhizobium bacteria).
 Mixed cropping,
 Crop rotation,
 Field fellow
 Making compost,
 Vermicomposting.
 TESTING THE PRESENCE OF STARCH
 Take a potted plant with broad leaves.
 Take two strips of black paper and cut out a small
square in their centers.
 Cover a part of two leaves with these papers and
secure them with paper clips .
 Keep the plant in the sunlight for 2–5 days.
 Observe the difference in the colour of the
covered and the uncovered portions on the one
leaf.
 Perform iodine test on this leaf. Did the two parts
show any difference in results?
 Now take another leaf.
 Remove the strip and expose the covered part to
the sunlight for 2–3 days and do the iodine test
again.
QUESTION 1
QUESTION 2
QUESTION 3
 SUMMARY
 All organisms take food and utilize it to get energy for the growth and maintenance of their
bodies.
 Green plants synthesize their food themselves by the process of photosynthesis. They are
autotrophs.
 Plants use simple chemical substances like carbon dioxide, water and minerals for the
synthesis of food.
 Chlorophyll and sunlight are the essential requirements for photosynthesis.
 Complex chemical substances such as carbohydrates are the products of photosynthesis.
 Solar energy is stored by the leaves with the help of chlorophyll.
 Oxygen is produced during photosynthesis.
 Oxygen released in photosynthesis is utilized by other living organisms for their survival.
 Fungi derive nutrition from dead, decaying matter. They are saprotrophs. Plants like cuscuta
are parasites.
 They take food from the host plant.
 A few plants and all animals are dependent on others for their nutrition and are called
heterotrophs.