Chapter - 01
Class 07 (Science)
Nutrition in plants
NUTRITION:- It is the mode of taking food by an organism and its utilization by the body.
NUTRIENTS:- The components of food that provide nourishment to the body are called nutrients.
# The components of food are
1* Carbohydrate
2* Protein
3* Fat
4* Vitamins
5* Minerals
# All organisms take food and utilize it to get energy for the growth and maintenance of their bodies.
# Plants can synthesise food for themselves but animal as well as human can not.
Modes of nutrition—> On the basis of different mode of nutrition, organisms are categorised into two major types-
AUTOTROPHS:- Auto = Self
Trophs = Nourishment
The mode of nutrition in which organisms make food themselves from simple substances is called autotrophic nutrition. Plants which are make their own food called autotrophs.
HETEROTROPHS:- Hetero = Other
Trophs = Nourishment
Animal and most other organism take food prepared by plants. They are called heterotrophs.
Mode of nutrition in plants:- Plants are the only organisms that can prepare food for themselves by using water carbon dioxide and minerals. The raw materials are present in their surroundings.
# The nutrients enable living organisms to build their bodies to grow, to repair damaged parts of their bodies and provide the energy to carry out life process.
PHOTOSYNTHESIS:- It is food making process in plants. Green plants prepare their own food with the help of carbon dioxide and water taken from the environment in presence of sunlight and chlorophyll for the manufacture of food. This process is known as photosynthesis.
# Leaves are the food factories of plants.
# Roots absorbed water from soil and transported to the leaves.
# Carbon dioxide from air is taken through stomata
STOMATA:- They are tiny pores present on the surface of leaves. These pores are surrounded by ‘guard cells’. It also act as process of transpiration.
-*- Water and minerals are transported to the leaves by the vessels. Which run like pipe throughout the root the branches and the leaves.
CHLOROPHYLL:- The leaves has a green pigment called chlorophyll. It helps leaves to capture the energy of the sunlight. This energy is used to synthesise food from carbon dioxide and water.
Photo = Light
Synthsis = To combine
Chlorophyll, sunlight, carbon dioxide and water are necessary to carry out the process of photosynthesis.
CO2 + H2O --sunlight & chlorophyll---> C6H12O6+6O2
-*- Solar energy is captured by the leaves and stored in the form of food.
-*- Sun is ultimate source of energy for all living organisms.
-*- Oxygen is produced during photosynthesis. Which is utilised by living organisms for their survival.
-*- The presence of starch in leaves indicates the occurrence of photosynthesis. Starch is also carbohydrate.
-*- Some leaves are not green in colour but they have also chlorophyll. The large amount of red, brown and other pigments mask the green colour photosynthesis takes place in these leaves also.
-*- Algae can also prepare their own food by photosynthesis.
CELL :- It is the smallest unit of life. Cells are the structural and functional unit of the body of all living organisms.
It can not visible by the naked eye. The cell has a thin outer boundary called cell membrane, a distinct, centrally located spherical structure called nucleus and jelly the substance surrounding the nucleus called cytoplasm.
Cell may contain following cell organelles:
1* Cell membrane
2* Cell wall
3* Ribosomes
4* Nucleus
5* Cytoplasm
6* Mitochondria
7* Plastids
8* Endoplasmic reticulum
9* Golgi apparatus etc.
SYNTHESIS OF PLANT FOOD OTHER THAN CARBOHYDRATES: - Carbohydrates are made of carbon, hydrogen and oxygen. These are used to synthesise other component of food such as proteins and fat.
-*- Protein contains nitrogenous substances like nitrogen.
-*- Plants can not absorb nitrogen in gaseous form.
-*- Soil has some bacteria that convert gaseous nitrogen into a usable form and release it into soil. These are absorbed by the plants along with water.
OTHER MODE OF NUTRITION IN PLANTS:-
There are some plants which do not have chlorophyll. They can not synthesise food. They use the heterotrophic mode of nutrition.
PARASITES:- A parasite is a heterotroph that completely depends on another organism for its food.
Ex. Cuscuta (Amerbel)
# Cuscuta does not have chlorophyll. It takes readymade food from the plant on which it is climbing.
# A parasite is a plant or an animal that lives on, or with, or inside a larger species extracting nutrients. In some cases, the parasite can harm the host and in other situation, it is completely harmless.
TYPES OF PARASITE :-
(1)- Partial parasites :- It obtain some of their nutrition from the host.
Ex. Painted cup
(2)- Total parasites :- It dependent completely on the host for nutrition.
Ex. Mistletoe
HOST:- The plant on which parasite climb is called the host.
INSECTIVOROUS PLANTS:- Plants that feed on insects are called insectivorous plants.
These plants are green and carry out photosynthesis, but they grow in nitrogen deficient soils. So, in order to get nitrogen, they feed on insects.
These insectivorous plants have their parts modified for attracting and catching insects.
Ex. Pitcher plant, Venous flytrap
PITCHER PLANT:- Pitcher like structure is the modified part of leaf. Apex of the leaf forms a lid which can open and close the mouth of the pitcher. Inside pitcher hair directed downward when an insect lands in the pitcher, the lid closed and the insect is trapped. The insect is digested by the digestive juices secreted in the pitcher and its nutrients are absorbed.
SAPROTROPHS :- The mode of nutrition in which organisms take in nutrients from dead and decaying matter is called saprotrophic nutrition.
Such organism with saprotrophic mode of nutrition are called saprotrophs.
Ex. Mushrooms, moulds and certain types of fungi and bacteria.
SYMBIOSIS:- Mode of nutrition in which two different individuals associate with each other to fulfill their requirement of food and shelter.
Ex. Lichens
A chlorophyll containing partner. Which is an algae and a fungus live together. The fungus provide shelter, water and minerals to the algae and it returns to fungus prepare food.
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