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Photosynthesis- Introduction

Before testin...

Question

Before testing the leaf for starch at the end of the experiment "Light is necessary for photosynthesis":
(a) In which liquid the leaf should be boiled?
(b) Why should the leaf should be boiled in this liquid?

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Solution

(a) The leaf should be boiled in alcohol (ethanol).
(b) The leaf is boiled in alcohol to destarch it (remove the chlorophyll from the leaf) as the chlorophyll interferes with the testing of starch with iodine.

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Q. Before testing the leaf for starch at the end of the experiment, ‘light is necessary for photosynthesis’, the experimental leaf should be boiled in:

(1) Water
(2) Alcohol
(3) KOH solution
(4) Hydrochloric acid

Q. A student is performing an experiment to show that sunlight is necessary for photosynthesis. In the first stage, he keeps a potted plant with green leaves in a dark place for about 3 days. Towards the end of the experiment, he boils one leaf in alcohol before using iodine for testing starch.
(a) Why is the plant kept in a dark place for about 3 days?
(b) Why is the leaf boiled in alcohol before testing for starch with iodine?

Q. When asked to set up an experiment to show that ‘light is necessary for photosynthesis’, a student ran to the school garden and set up the experiment by using a plant growing in the school garden. The experiment failed. His classmates made the following suggestions to get success in the experiment:
Student A : Safranin should be used instead of iodine
Student B : The leaf should not be boiled in alcohol to remove chlorophyll before testing for starch
Student C : Transparent paper should be used instead of black paper strip.
Student D : The leaf should be destarched before starting the experiment
The correct suggestion is given by :
(1) student A
(2) student B
(3) student C
(4) student D

Q. Why is the leaf boiled in alcohol before the test for starch in iodine solution??

Q. In the experiment to show that sunlight is necessary for photosynthesis:
(a) What is done to destarch the green leaves of the potted plant initially?
(b) What is done to a part of destarched leaf so that photosynthesis may not take place in that part of the leaf (before keeping the potted plant in sunlight)?
(c) How is chlorophyll removed from the green leaf before further testing?
(d) Which reagent is used to test the presence/absence of starch in the parts of experimental leaf?

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