Q. Give alongside is the diagram of an experimental set-up:
  1. What is the objective of the experiment?
  2. Will it work satisfactorily? Give reasons.
  3. What alteration(s) will you make in it for obtaining expected result?
  4. Would you take any step before starting the experiment? Describe this step and explain its necessity.

Dear student,      
Please find below the solution to the asked query                                                              

1. The objective of the experiment is to show the necessity of carbon dioxide in the process of photosynthesis.

2. Yes, the set up will work satisfactorily but there will no way of comparing the results. Lime water present inside the flak will absorb all the carbon dioxide present in it and so, the leaf present in it will not undergo photosynthesis. When it will be tested for the presence of starch, it will show negative result and this will prove the necessity of carbon dioxide for photosynthesis.

3. In the given set up, the leaf should be set in such a way that half of it would be outside the flask and the other half inside the flask. The part of leaf outside the flask will photosynthesize as it will get carbon dioxide from the atmosphere. Hence, we can compare result that we got from the leaf present inside the flask.

4. Step to be taken before starting the experiment will be- to destarch the leaf.  This can be done by placing the plant in a dark room for 2-3 days so that it will not be able to carry out photosynthesis and the stored starch will also be consumed by the plant.
If starch is already present at the beginning of the experiment the results will not be accurate. Hence, it is important to start off with a plant without starch (full leaf will show the presence of starch and this will prove that it has undergone photosynthesis even in absence of carbon dioxide).

Hope this information will clear your doubts about the topic.   
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