1. Complete Activity 1.1 (Page 3). Take two potted plants of the same kind. Keep one in the dark (or in a black box) for 72 hours and the other in sunlight. Perform iodine test with the leaves of both the plants as you did in Class VI. Record your results. Now leave the pot which was earlier kept in the dark, in the sunlight for 3 – 4 days and perform the iodine test again on its leaves. Record your observations in your notebook.
Answer:
The above activity can be carried out as follows:
Aim: To observe how the plants kept in the dark and sunlight respond to the iodine test and make the necessary conclusions.
Materials Required: Two potted plants of same kind, two test tube, beaker, ethanol, iodine.
Procedure:
(i) Keep one potted plant in a dark room or in a black box for 72 hours and keep the other potted plant of the same kind in sunlight for 72 hours.
(ii) Perform iodine test on the leaves of both plants. Take one leaf from each plant, place each in a separate test tube and pour spirit to completely immerse the leaf. Now place each test tube in the beaker half filled with water and heat the beaker until the green colour from the leaf comes out into the spirit in the test tube. Now extract each leaf, rinse carefully with water and pour some iodine solution on each. Note the observations.
(iii) Now place the pot which was earlier in the dark, in the sunlight for 3 – 4 days and perform the iodine test again on its leaves. Note the observations.
Observations: We observe that:
- Initially Plant A which was kept in the dark did not change the colour of iodine and Plant B which was kept in sunshine changed the colour of iodine to blue-black.
- Then when Plant A was kept in the sunlight for 3 – 4 days, it turns iodine to blue-black.
Conclusions: We conclude that leaves produce starch in the presence of sunlight by the process of photosynthesis. The starch present in leaves changes the colour of iodine to blue-black.
“Take two potted plants of the same kind. Keep one in the dark (or in a black box) for 72 hours and the other in sunlight. Perform iodine test with the leaves of both the plants as you did in Class VI. Record your results. Now leave the pot which was earlier kept in the dark, in the sunlight for 3 – 4 days and perform the iodine test again on its leaves. Record your observations in your notebook.” – Solved.
Related Links:
Solution to Extended Learning Problem 1
Solution to Extended Learning Problem 2
Solution to Extended Learning Problem 3
Solution to Activity 1.2
