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Test for Carbohydrates

A star-shaped...

Question

A star-shaped figure was cut in the black paper strip used for covering the leaf of a destarched plant used for demonstrating that light is necessary for photosynthesis. At the end of the experiment when the leaf was tested for starch with iodine, the star-shaped figure on the leaf was found to be:

(1) colourless
(2) green in colour
(3) brown in colour
(4) blue-black in colour

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Solution

The star shaped figure would be found to be blue black in colour indicating the presence of starch in that area.

Hence, the correct answer is option 4.

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Similar questions

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 destarched leaf of a potted plant is partially covered with black strip of paper on the upper
and lower surfaces as shown in the figure and kept in sunlight. The starch test was
performed after this. What will be the colour of the regions marked as A and B in the leaf ?

Q. A portion of destarched leaf of a potted plant was covered with a black strip of paper. The plant was then exposed to sunlight for six hours and then tested for starch. It was observed that:
(1) both covered and uncovered parts of leaf turned blue-black
(2) both covered and uncovered parts of leaf turned yellow-brown
(3) only the uncovered part of leaf turned blue-black
(4) only the covered part of leaf turned blue-black

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

Q. Which one of the following is the correct combination of relevant materials required for setting up an experiment to show that light in necessary for photosynthesis?
(1) destarched leaves, strips of black paper, starch solution, and iodine crystals
(2) a potted plant, strips of coloured paper, starch solution, iodine and potassium iodide
(3) destarched leaves, strips of black paper, starch solution, and potassium iodide
(4) destarched leaves, strips of black paper, and iodide solution

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