22. Higher Order Thinking Skills (HOTS) II

Imagine that student \(A\) studied the importance of certain factors in photosynthesis. He took a potted plant and kept it in dark for \(24\ hours\). 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. Why was the plant kept in the dark before the experiment?
 

c. How will you prove that starch is present in the leaves?
 

d. Name the raw materials needed for photosynthesis.

 

i. The student aimed to study the role of watersunlightcarbon dioxide and its effect on the process of photosynthesis.

 

ii. The plant was placed in the dark before the experiment to remove chlorophyll from the leafremove starch from the leavesto prove transpiration.

 

iii. The potted plant is placed in sunlight for few hours. The leaf covered with black paper was plucked and the black paper should be removed. The leaf is then immersed in boiling wateriodine solution for few minutes.

 

iv. Then, the leaf is immersed in alcohol to remove moistureremove chlorophyll.

 

v. Next, the presence of starch in leaves can be proved by performing the starch test using iodine solutionalcohol.

 

vi. The covered part of the leaf does not turn blue-blackturns blue-black in colour, while the uncovered part of the leaf turns blue-blackdoes not turn blue-black in colour. From this experiment, we can say that the portion of the leaf that was uncovered receives all the necessary photosynthesis factors. Hence, the reaction of photosynthesis occurred only at that place and not at the covered portion.

 

vii. The raw materials required for photosynthesis includes watercarbon dioxidechlorophyllsunlightall of the above.