A potted plant was taken in order to prove a factor necessary for photosynthesis. The potted plant was kept in the dark for 24 hours. One of the leaves was covered with black paper in the centre. The potted plant was then placed in sunlight for a few hours.

(c) During the starch test, why was the leaf -
(1) boiled in water
(2) boiled in methylated spirit

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Solution

During the starch test -
1. The leaf is boiled in water for a minute to kill the cells and also to remove the waxy cuticle which might interfere with the iodine test.
2. The leaf was boiled in methylated spirit over a water bath to remove the chlorophyll content of the leaf. It turns pale-white when boiled in alcohol.

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A potted plant was taken in order to prove a factor necessary for photosynthesis. The potted plant was kept in the dark for 24 hours. One of the leaves was covered with black paper in the centre. The potted plant was then placed in sunlight for a few hours.

(a) What aspect of photosynthesis was being tested ?

(b) Why was the plant placed in the dark before beginning the experiment ?

(1) boiled in water (2) boiled in methylated spirit.

(d) Write a balanced chemical equation to represent the process of photosynthesis.

(e) Draw a neat diagram of a chloroplast and label its parts.

A candidate studied the importance of certain factors in photosynthesis. He took a potted plant and kept it in the dark for over 24 hours. In the early hours of the next morning, he covered one of the leaves with dark paper in the centre only. Then he placed the plant in sunlight for a few hours and tested the leaf which was covered with black paper for starch.

(a) What aspect of photosynthesis was being investigated ?

(b) Is there any control in this experiment ? If so, state it.

(d) Describe step by step, how the candidate proceeded to test leaf for the presence of starch.

Q. How does carbon dioxide return to the atmosphere? Explain.
A student in order to study the importance of certain factors of photosynthesis took a potted plant and dept it in the dark for over 24 hours. Then in the early hours of the morning the student covered one of the leaves with black paper in the centre only. Student placed the potted plant in the sunlight for a few hours, and then tested the leaf which was covered with black paper for starch.
(i) What aspect of photosynthesis was being investigated?
(ii) Is there any control in this experiment? If so, state the name.
(iii) Why was the plant kept in the dark before the experiment?
(iv) Describe step by step how the candidate proceeded to test the leaf for the presence of starch.

Q. The steps taken for setting up an experiment to demonstrate that ‘light is necessary for photosynthesis’, were as follows :
• A strip of black paper was clipped on the leaf of a potted plant
• The plant was kept in the sun for four hours
• The strip was removed and the leaf was placed in boiling alcohol in water bath
• The leaf was washed and tested for starch
The result was not as expected. Identify the step which had been missed out :
(1) The plant was kept in the dark for 24 hours before starting the experiment
(2) The leaf was boiled in water after placing it in boiling alcohol
(3) The leaf was sprinkled with water before placing it in black paper strip
(4) A transparent strip was used to cover the black paper strip

Q. A potted plant was taken in order to prove a factor necessary for photosynthesis. The potted plant was kept in the dark for 24 hours. One of the leaves was covered with black paper in the centre. The potted plant was then placed in sunlight for a few hours.

(a) What aspect of photosynthesis was being tested?

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