A healthy croton plant bearing variegated leaves was kept in a dark cupboard to destarch it, after which it was placed in sunlight for a few hours. One of the leaves was then plucked and an outline of the leaf making the green and non-green regions were drawn. The leaf was then tested for starch. Using the above information, answer the following question

Why is the leaf boiled in water and alcohol before testing for the presence of starch?

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Solution

The leaves are boiled in water and alcohol before testing for the presence of starch because the cells are killed by boiling and chlorophyll is dissolved in alcohol.

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A healthy croton plant bearing variegated leaves was kept in a dark cupboard to destarch it, after which it was placed in sunlight for a few hours. One of the leaves was then plucked and an outline of the leaf making the green and non-green regions were drawn. The leaf was then tested for starch. Using the above information, answer the following question

Give the chemical equation to represent the process of starch formation in plants.

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

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. In an experiment to test the presence of starch in a leaf, the plucked leaf is first boiled in water for a few minutes. This is an important step in the experiment because it :
(1) converts glucose made in the leaf into starch
(2) dissolves chlorophyll present in the green leaf
(3) extracts starch to destarch the leaf
(4) makes the leaf more permeable to iodine solution

Q. A leaf of destarched healthy potted plant was covered by black paper strip as shown in Figure I, and kept in sunlight in the morning. In the evening, it was plucked off and tested for the presence of starch by using iodine solution.

The observation is matched with the Figure No.:
(1) II
(2) III
(3) IV
(4) V

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