Mode of Nutrition in Plant - Autotrophic Nutrition




Autotrophic Nutrition:-

Carbon and energy requirements of the autotrophic organism are fulfilled by photosynthesis.

It is the process by which autotrophs take in substances from the outside and convert them into stored forms of energy. This material is taken in the form of carbon dioxide and water which is converted into carbohydrates in the presence of sunlight and chlorophyll. Carbohydrates are utilised for providing energy to the plant. We will study how this takes place in the next section. The carbohydrates which are not used immediately are stored in the form of starch, which serves as the internal energy reserve to be used as and when required by the plant. A somewhat similar situation is seen in us where some of the energy derived from the food we eat is stored in our body in the form of glycogen.

Autotrophs use simple inorganic substances and convert it into complex high energy molecules.

Autotrophic nutrition is fulfilled by the process by which autotrophs take in CO2 and H2O and convert these into carbohydrates in the presence of chlorophyll, sunlight is called Photosynthesis.

  • Sunlight: It is an inorganic material

  • Chlorophyll: Sunlight is absorbed by chlorophyll

  • CO2: Enters through stomata and oxygen is released as a by-product through stomata on leaf

  • Water: water + dissolved minerals like nitrogen, phosphorus etc are taken up the roots of the soil

Site Of Photosynthesis

Some cells contain green pigments which are cell organelles called chloroplasts which contain chlorophyll.

some cells contain green dots. These green dots are cell organelles called chloroplasts which contain chlorophyll.

(i) Absorption of light energy by chlorophyll.

(ii) Conversion of light energy to chemical energy and splitting of water molecules into hydrogen and oxygen.

(iii) Reduction of carbon dioxide to carbohydrates.

Water used in photosynthesis is taken up from the soil by the roots in terrestrial plants. Other materials like nitrogen, phosphorus, iron and magnesium are taken up from the soil. Nitrogen is an essential element used in the synthesis of proteins and other compounds.


  • Stomata are tiny pores present on the surface of the leaves.
  • Stomata does the exchange of large amounts of gases (O2/CO2)
  • Stomata is responsible large amounts of water is lost through the stomata,
  • The opening and closing of the pore is a function of the guard cells. The guard cells swell when water flows into them, causing the stomatal pore to open. Similarly the pore closes if the guard cells shrink.
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Life Processes part 4 (Nutrition Introduction) [00:07:28]

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