Sarthaks Test
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Some experiments were carried out using Croton sp. plants to understand the process of photosynthesis. It was observed that the leaves of the plant exposed to light for longer duration accumulated more starch. However, due to presence of pre-formed starch in the leaves, it was difficult to find the net productivity on a fixed exposure to light source. Therefore, it was necessary to obtain starch free leaves in the plant before starting the experiment.

1. Which of the following would help obtain starch free leaves in the plant? 

(a) Expose the leaves to blue light for 48 hours before starting the experiment. ;

(b) Keep the plant in dark for about 48 hours before starting the experiment.

(c) Remove starch from the leaves by exosmosis, 48 hours before starting the experiment.

(d) Keep the leaves to red light for 48 hours before starting the experiment.

2. After a period of illumination, the leaves were boiled in alcohol to make them colourless. Which of the following could be used to test the end product stored in the leaves? 

(a) Cobalt chloride paper

(b) Litmus paper

(c) Iodine solution

(d) Copper sulfate solution

3. During the experiment it was also noted that the end product starch got accumulated only in the cells containing green plastid and upon their illumination to specific wavelengths of light. What is the immediate purpose of the specific wavelength of light used ? 

(a) In reducing carbon dioxide

(b) For synthesis of glucose

(c) Excitation of chlorophyll

(d) Splitting water into oxygen and hydrogen ion.

4 Some of the starch free leaves were coated with wax on both the surfaces. The plant was maintained under, normal environmental conditions. At the end of the experiment, the wax coated leaves are likely to show 

(a) Accumulation of more water.

(b) Wilting of the wax coated leaves.

(c) Increase in sucrose accumulation. ..

(d) Decrease in number of chloroplasts

5. During the morning hours, using a fine blade, an incision was made to the leaves such that the phloem tissue was cut open. Analysis of the liquid oozing out was found to contain high amount of

(a) Xylose

(b) Ribose

(c) Sucrose

(d) Galactose

6. Leaves of the plant were homogenized in an appropriate buffer environment under appropriate temperature conditions in a test tube. In which of the following conditions is photosynthesis likely to happen in the homogenate? 

(a) As long as the test tube is illuminated by white light and oxygen concentration is high.

(b) As long as the test tube is illuminated by white light and sodium bicarbonate is present in it.

(c) As long as oxygen concentration is high and sodium carbonate is present in the test tube.

(d) As long as the test tube is illuminated by white light and potassium phosphate is present in it.

1 Answer

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1. (b) The starch free leaves can be obtained by keeping the plant in dark, so that already present starch is utilized in 48 hrs.

2. (c) Starch presence can be tested by adding iodine solution which gives bluish black colour of starch – iodine mixture.

3. (c) Purpose of illumination to specific wavelengths of light is the excitation of chlorophyll (light reaction).

4. (b) Wilting occurs due to wax blocks the transpiration so water transportation inhibits.

5. (c) The transport of glucose, occurs in the form of sucrose, in phloem therefore, when cell sap oozes out, liquid contains sucrose

6. (b) Photosynthesis will occur till the test tube is illuminated with white light & sodium bicarbonate is present which yields CO2 in solution.

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