Photosynthesis Process in Plants

Photosynthesis Process in Plants

Photosynthesis is a process in which green plants synthesise their food, like glucose, from carbon dioxide and water in the presence of sunlight with the help of chlorophyll.

Essential Requirements for Photosynthesis

Carbon dioxide, water, chlorophyll and sunlight are necessary for photosynthesis.

• Terrestrial plants take CO₂ from the atmosphere, whereas aquatic plants use carbon dioxide dissolved in water.

• Water enters into the cells of the leaves through osmosis and CO₂ through diffusion from the atmosphere or release during respiration.

• Water necessary for photosynthesis is absorbed by the roots.

• Oxygen produced during photosynthesis is due to photolysis of water.

Role of Chlorophyll

• The green colour of the plants is due to the presence of chlorophyll.

• Chlorophyll are photoreceptor molecules, which trap the solar energy.

• There are different types of chlorophyll molecules, like ‘a’, ‘b’, ‘c’, ‘d’ & ‘e’.

• Chlorophyll ‘a’ & ‘b’ are most common and are found in plants.

• Photosynthesis converts light energy into chemical energy.

• There is an atom of magnesium in the centre of chlorophyll.

• Chlorophyll absorbs the violet, blue and red colours of light.

• The rate of photosynthesis is maximum in red light and is minimum in violet light.

• Green light is least effective in photosynthesis.

Nature of the Process

• The process of photosynthesis is a reaction of oxidation and reduction.

• Oxidation of water takes place, producing oxygen, and reduction of carbon dioxide takes place, forming glucose.

The Stages of Photosynthesis

1. Photochemical Reaction or Light Reaction

2. Dark Chemical Reaction

1. Photochemical Reaction (Light Reaction)

• This reaction is completed in the grana of the chlorophyll.

• This is also called the Hill reaction.

• In this process the breaking down of water takes place, releasing hydrogen ions and electrons.

• For photolysis of water, energy is received from the light.

• At the end of this process, ATP is formed from ADP & P.

2. Dark Chemical Reaction

• This reaction takes place in the stroma of chlorophyll.

• In this reaction reduction of carbon dioxide takes place, and sugar or starch is formed.

• It is also known as the Calvin-Benson cycle.

Additional Information Related to Photosynthesis

• Root pressure is measured by an auxanometer.

• The cells which are closely associated and interacting with guard cells are subsidiary cells.

• The conversion of starch to sugar is essential for stomatal opening.

• The cactus plant keeps its stomata open during the night and closes them during the daytime.

• The molecule which mainly absorbs light energy and converts it to chemical energy in photosynthesis is chlorophyll ‘a’.

• Leghaemoglobin is a protein pigment present in the nodules of roots that helps in protecting nitrogenase from oxygen molecules.

Final Thoughts

Photosynthesis is the process by which green plants make their own food, like glucose, from carbon dioxide and water in the presence of sunlight and chlorophyll. Chlorophyll, the green pigment in leaves, traps solar energy and helps convert light energy into chemical energy.

This process releases oxygen through the photolysis of water. Photosynthesis occurs in two stages — the light reaction in the grana, where ATP is formed, and the dark reaction in the stroma, where glucose or starch is produced.

The rate of photosynthesis is highest in red light and lowest in violet light. This vital process maintains life by producing food and oxygen for all living organisms.