Nutrition :- nutrition is the process of taking food by an organism and its utilisation by the body.

Mode of nutrition

On the basis of different mode of nutrition, organisms are  categorised into two major type-

1. Autotrophics(auto-self ,trophos -nourishment) :– it is the mode of nutrition in which organisms make their own food from simple substance (eg.co2 and H2o) by the process of photosynthesis.

2. Heterotrophs( heteros-other) :- organisms which  cannot prepare their own food and take food from green plants and animals are called heterotrophs and the mode of nutrition is called heterotrophic nutrition.


(Photo=light , synthesis=to combine)-photosynthesis is the process of synthesis of food (glucose) from carbon dioxide and water, using solar energy by chlorophyll pigments.

During the process oxygen is released. Glucose ultimately converted into starch.

The process of photosynthesis take place in green leaves, there fore leaves are referred to us the “food factories of plants”.

Requirements in photosynthesis

1. Co2 :- Co2 is taken from air through the tiny pores present on the surface of leaves called stomata.

2. Water :- Water is absorbed through the roots of plants and transported to leaves by vessels which act like pipes.

3.Chlorophyll :- Green plants posses chlorophyll in their leaves which capture the energy of sunlight.

4.Sunlight :- Sun is the natural source of sunlight, which provide solar energy to the plant, solar energy is converted into chemical energy by plants through photosynthesis. Thus sun is the ultimate source of energy.

Importance of photosynthesis

1. If the plants do not perform photosynthesis there would be no food on earth, photo synthesis is also necessary.

 2. For the production of oxygen gas in atmosphere which is necessary for respiration of organisms.therefore,it can be said that no life is possible in the absence of photosynthesis.

Role of leaf in photosynthesis

Stomata present on the leaf which is helps in gaseous exchange at the time of photosynthesis.

Stomata :- The tiny pores present on the surface of the leaves surrounded by two kidney shaped guard cells are called stomata. Guard cells regulate the opening and closing of stomata.

Functions of stomata

1.Carbon di oxide from air is taken in and Oxygen is released through stomata.

2.Transpiration takes place through stomata.


Synthesis of food other than carbohydrates

Plant synthesize carbohydrates through the process of photosynthesis.

The carbohydrates are made of carbon, hydrogen and oxygen.

Some times these simplest forms of carbohydrate are utilised to synthesise other nutrients like fats(oil), proteins.

Sometimes the starch or glucose is stored in the form of oil in their seed(oil seed). Eg . sunflower

When the plant nutrient  contains,carbon,hydrogen,and oxygen along with nitrogen elements, it is called protein.

Therefore, plants also make fats and proteins as their food other than carbohydrates.

Other modes of nutrition in plants

There are some plants which do not contain chlorophyll in them, thus cannot prepare their own food. These plants obtain their food from other plants or animal, they are called heterotrophic plants. They are-

1.Parasitic plants :- the plant which obtains their food from other living organism is called a parasite and the living organism from whose body, food is obtained is called host.

Example:- Amarbel or cuscuta (through-special roots)

2.Insectivorous plants :- These plants are green in colour but lack nitrogen overcome this problem, these plants eat insects. Hence they are called insectivorous plant or carnivorous plants.

Example:- Pitcher plant , sundew , Venus flytrap, and bladder wort.

Since ,they can synthesise their own food but fulfil their nitrogen deficiency by eating insects, therefore these are called as partial heterotrophs.

Saprotrophic plants :- The mode of nutrition in which organisms take their nutrients from dead and decaying matter is called saprotrophic nutrition.

Plants which use saprotrophic mode of nutrition are called saprotrophs .

Example :- Nongreen plants like fungi (yeast, bread moulds, mushrooms)

Symbiotic plants :- The relationship in which two different organisms live together and share shelter and nutrients is called symbiotic relationship .

Example :- Lichen and Rhizobium

Lichen is an association in which an algae and a fungus live together. The fungus provides shelter, water and minerals to the algae and in return, the algae provide food which it prepare by photosynthesis.

Replenishment of nutrients in soil

Rhizobium bacteria live in the root nodules of leguminous plants. These bacteria take nitrogen gas from the atmosphere and convert it into water soluble nitrogen compounds making it available to the leguminous plants for their growth.

In return, leguminous plants provide food and shelter to the bacteria as rhizobium can not prepare itsfood.they thus have a symbiotic relationship.

This association is very important for the farmers, as they do not need to add nitrogen fertilizers to the soil in which leguminous plants are grown.