The Process of Photosynthesis


“Photosynthesis is a physicochemical process in which green plant synthesise their food from atmospheric carbon dioxide and water in presence of sunlight and chlorophyll.“

  • Entire living population including human beings need food for energy and growth. Food is obtained from green plants. Green plants prepare their food with the help of Photosynthesis.
  • It is a very important process for two main reasons, first, it is the primary source of food on earth; second, it is also responsible for release of oxygen in the atmosphere around Earth.

Process of Photosynthesis

The main events in this process are as follows –

  • Absorption of light energy by chlorophyll: Leaves of Green plant contain chloroplast which consists of green pigment called chlorophyll. Chlorophyll absorb light energy.
  • Light Reaction or the Photochemical Phase: The absorbed light energy is converted by chlorophyll into chemical energy which is stored as ATP. Plant roots absorb water from the soil which is then transported to leaves of the plant and other parts. In the chloroplast the chemical energy is used to split water molecules producing hydrogen and oxygen. Oxygen formed during this phase is released in the atmosphere.
  • Dark Reaction: The surface of green leaves has small pores called stomata. Carbon dioxide molecules enter in the leaves through stomata. In the stroma of chloroplast, hydrogen produced during light reaction is used to reduce carbon dioxide into glucose. Excess of glucose is stored in the form of carbohydrates in the fruit or foodgrains of the plant.
  • It is not necessary that all these steps take place at the same time. e.g. In desert, plants absorb carbon dioxide during night and prepares an intermediate product. During day when sunlight is available this product is converted to carbohydrates.

All courses blog promo

Photosynthesis equation

Photosynthesis CBSE Class 10 Life Processes

Site of Photosynthesis

Photosynthesis occur in chloroplasts. Since chloroplasts are only present in green plants hence only green plants can produce food by photosynthesis.

Raw Materials for Photosynthesis

For the process of photosynthesis plant need carbon dioxide, water, chlorophyll and sunlight.

  • Chlorophyll: Chlorophyll is a green pigment present in chloroplasts of the leaves. It is responsible for trapping solar energy from sunlight and converting it into chemical energy.



    • Activity to demonstrate chlorophyll is essential for photosynthesis

      • Keep a plant in dark for 3 days, and then place the plant in sunlight for 6 hours. So that Plant use up reserved starch and produce new starch.
      • Take a leaf of that Plant which have varying color levels. keep the leaf in boiling water for few minutes. After this process the leaf becomes soft and loose.
      • Immerse the leaf in alcohol and place alcohol containing beaker in water bath and heat till alcohol boils. The leaf become brittle and its color changes to pale yellow. The color of alcohol changes to pale green.
      • Dip the leaf in dilute solution of iodine. Remove the leaf and rinse off the leaf. Because of starch produced in photosynthesis process some areas on leaf becomes blue-black. This confirms that chlorophyll is essential for photosynthesis.

      Carbon Dioxide: Intake of carbon dioxide and removal of oxygen is called gaseous exchange. It takes place at surface of stem, roots and leaves.Tiny pores present on surface of leaves called as stomata are responsible for gaseous exchange. Large amount of water can also lost through these stomata hence guard cells facilitates opening and closing of stomatal pores whenever needed. For making food, in the form of glucose the necessary raw material is carbon dioxide. Here is activity to demonstrate Carbon dioxide is essential component of photosynthesis process.

      Activity:

      • Take two healthy potted plants of same height and place them in dark room for three days. During these days plant use up reserved starch.
      • Place each plant on glass plates and place watch glass containing sodium hydroxide near one plant. Cover plants with separate bell-jars and seal their bottom with vaseline. Sodium hydroxide absorbs carbon dioxide present in one jar leaving no carbon dioxide for photosynthesis.
      • Keep plants in sunlight for two hours and check a leaf of each plant for starch. The leaf of plant placed near sodium hydroxide does not produce starch while other plant produces starch.

      Hence, it is confirmed that carbon dioxide is essential for photosynthesis.

      Water: Water is essential for photosynthesis as it is a source of hydrogen required to carry out reduction of carbon dioxide into glucose. Absence of water causes stomata to close reducing CO2 availability for photosynthesis. Moreover it also makes plant leaves wilt reducing the surface area of absorption of sunlight and carrying out metabolic activities.

      Sunlight: The energy for photosynthesis process is obtained from sunlight. Chlorophyll pigment absorb all colors present in sunlight however the absorption of green color is relatively lower. This means that it reflects green color most and therefore leaves of plant appear green. To find if sunlight is essential for photosynthesis or not one can keep a potted plant in dark for some days and test for presence of starch in the leaf. During some days plant utilize stored starch however as sunlight is not present starch can’t be produced.

      Watch video on Photosynthesis –

      embed]https://www.youtube.com/watch?v=oHwvW2_i2f4[/embed]

      This article is helpful for Class 10 Science

      Keywords: Photosynthesis, Photosynthesis Equation, Raw materials for Photosynthesis, Site of photosynthesis, Autotrophic nutrition




      Related articles

      Cell Organelle And Their Functions
      Simple Permanent tissue In Plants
      Complex Permanent Tissue In Plants
      Periodic Table and Periodic Trends
      States of matter

Comments

  1. Anusha Shrivas

    Good explanation of topic. Where will i find all science videos?

    1. LearnFatafat

      Hi Anusha,
      To watch all science video you need to buy course of respective class. You can check all our product here

Your email address will not be published. Required fields are marked *

one + 2 =