Question

Describe an experiment to show that light is necessary for photosynthesis

Answer 1

Experiment on Photosynthesis-Sunlight is necessary for Photosynthesis |


Photosynthesis is a physiological process of green plants. One of the important factor required for photosynthesis is sunlight. In this resource I have explained in detail how an experiment can be conducted to prove the importance of the factor sunlight for this process. Along with the experiment I gave some important questions as well as answers related to the experiment which will be useful for those preparing for final practical or theory exams of various Boards.

Introduction

Photosynthesis is an important physiological activity of green plants. For photosynthesis to occur in green plant the factors required are Sunlight, Chlorophyll and Carbon dioxide. To prove the necessity of these factors there are certain specific experiments have to be in the laboratory. So students must know clearly how a particular experiment will be done for each factor clearly and also must realize why a particular step will be done for the success of the experiment with reasons.

Aim of the experiment:-

To prove Sunlight necessary for green plants to prepare their food.

Requirements:-

A well watered potted green plant, two strips of black papers, small clips, spirit lamp or bun sen burner, test tube, beaker, Petr-dish, water, mentholated spirit or rectified spirit or ethanol, iodine solution.

Sunlight is necessary for Photosynthesis experimental setup:- (Courtesy:-dev.elearn.punjab.gov.pk) 

Procedure for the experiment

Before starting the experiment to prove Sunlight is necessary for photosynthesis an important step has to be carried out is known as De-starching. De-starching is a process in which the starch present in the leaves will be eliminated by keeping the plant in dark room or closed cup-board for about 48 hours. This step is done to ensure that previously manufactured food in the leaves get consumed when the plant was kept in dark place since photosynthesis doesn't occur at that time.
Next strips of black paper will be arranged one on either side of the selected leaf of the De-starched plant with the help of clips. Now the whole plant is kept in bright Sunlight for about 3-4 hours. Then the strips of black papers are removed from the experimental leaf and then starch test or Iodine test is conducted for the experimental leaf. 

Answer 2

Explanation:

Aim: to prove that light is necessary for photosynthesis to from starch.

Apparatus: potted plant, light screen, iodine solution.

Procedure

Procedure:1) keep potted plant in dark room for one week to remove starch.

2) Take one black paper and cut it with your own design.

3) keep design paper properly on the both sides with the help of clips.

4) ensure that light does not passes through the covered area with black paper.

5) keep the arrange apparatus at sunlight available area.

6) after few hours exposure to bright sunlight detach the leaf.

7) boil the leaf in methyl spirit over water bath. ek becomes pale white due to the removal of chlorophyll. take the leap from test tube and spread the leaf in a dish.

8) at few drops of iodine on leaf. the parts of the leaf which could get light through the cut out design turns blue black colour.

9) the parts of the leaf which could not get light are not turn into blue black colour.

Result: this experiment prove that light is necessary to form starts in the process of photosynthesis.

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