Nutrition in Plants:

Plants obtain nutrition by a process called Photosynthesis.


  • The process by which green plants make their own food (like glucose) from carbon dioxide and water by using light energy (sunlight) in the presence of chlorophyll is called photosynthesis .
  • 'Photo' means ‘light’ and 'synthesis' means to ‘build’, thus 'photosynthesis' means 'building up by light'.

The process is chemically represented as:

Reaction for Photosynthesis -teachoo.jpg

Photosynthesis - Teachoo.jpg

Necessary conditions for Photosynthesis:

Necessary conditions for Photosynthesis - Teachoo.jpg

(1) Sunlight:

Sunlight provides energy required to carry out all the chemical reactions involved in the photosynthetic process.


(2) Carbon Dioxide:

  • The carbon dioxide gas enters the leaves of the plant through the stomata present on the surface. 
  • Stomata are tiny pores present on the surface of the leaf.
  • Each stomatal pore is controlled by guard cells
  • When water flows into guard cells, they swell up , become curved and cause the pore to open . On the other hand when guard cells lose water they shrink, become straight and close the stomatal pores.
  • he exchange of gases takes place due to the opening and closing of stomata.

Open and Closed Stomata - Teachoo.jpg

(3) Chlorophyll:

  • Chlorophyll is a green colored pigment .
  • Chlorophyll helps in the absorption of sunlight which provides energy for carrying out photosynthesis.

Chlorophyll - Teachoo.jpg

(4) Water and Minerals:

  • The water required by the plants for photosynthesis is absorbed by the roots of the plant from the soil. Water is transported to the leaves through the roots and stem.
  • The plants need other minerals such as nitrogen, phosphorus, potassium etc which are taken from the soil.


Site for photosynthesis:

  • Photosynthetic pigment chlorophyll occur in green coloured cell organelles called chloroplasts.
  • They absorb light energy and converted into chemical energy.
  • In a cross section of leaf, chloroplasts are found as green dots in the palisade and spongy cells of mesophyll.
  • Photosynthesis occurs in the mesophyll cells of green plants.
  • Epidermis is devoid of chloroplast except guard cells of stomata.

Stepwise Process of Photosynthesis:

Photosynthesis takes place inside Chloroplast .

The major steps involved in the process of photosynthesis are:

  1. Absorption of sunlight by chlorophyll
  2. Absorption of water , and obtaining carbon dioxide for conversion.
  3. Conversion of Chemical energy into light energy and splitting of water into hydrogen and oxygen by light energy.
  4. Reduction of carbon dioxide by hydrogen to form carbohydrates like glucose by utilizing the chemical energy (obtained by transformation of light energy)

Process of Photosynthesis : Flowchart

Photosythesis in green plant - Teachoo.jpg


The Reaction for Photosynthesis is as follows :

Reaction for Photosynthesis -teachoo.jpg

The oxygen released as a by-product is released into the air. 


Plants that do not have chlorophyll are heterotrophs .

  • Plants like the venus fly trap have chlorophyll, and photosynthesize, but they obtain their nutrients and minerals from the insects they trap.
  • C roton sp. Plants are plants with leaves that appear to be not green due to higher concentration of other colour pigments in the leaves. But since chlorophyll is also present , they carry out photosynthesis normally.  
  • Many plants are also parasitic/saprophytic in nature.
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Maninder Singh

CA Maninder Singh is a Chartered Accountant for the past 14 years and a teacher from the past 18 years. He teaches Science, Economics, Accounting and English at Teachoo