Question

Q18. Assertion:The teacher instructed a student to place a healthy potted flower plant in a dark
room for 24 hours prior to an experiment on photosynthesis.
Reason: The purpose of placing it in a dark room is to destarch the leaves.
a)Both assertion and reason are correct and reason is the correct explanation for assertion
b)Both assertion and reason are correct but reason is not the correct explanation for assertion
c)Assertion is correct but reason is incorrect
d)Both assertion and reason are incorrect
Q19. Assertion: On exposure to light, AgBr is covered with black surface.
Reason: Because it undergoes photochemical decomposition.
a)Both assertion and reason are correct and reason is the correct explanation for assertion
b)Both assertion and reason are correct but reason is not the correct explanation for assertion
c)Both assertion and reason are incorrect
d)Assertion is correct but reason is incorrect
Q20. Assertion:In the experiment ”light is essential for photosynthesis” to test the presence of starch
in the experimental leaf, the leaf is boiled in alcohol for few minutes in water bath .
Reason: The use of water bath is recommended because alcohol is flammable.
a)Both assertion and reason are correct and reason is the correct explanation for assertion
b)Both assertion and reason are correct but reason is not the correct explanation for assertion
c)Both assertion and reason are incorrect
d)Assertion is correct but reason is incorrect

Answer 1

Answer:

Explanation:

Starch which is a storage food in plants may vary from plant to plant. In sunlight, Calvin cycle goes on which produces continuous starch or remains in the form of starch. And if the experiment is still continued, then the experiment will show false results. So, to get positive yield at the end of experiment leaves should be destarched.