Boojho wanted to test the presence of starch in leaves. He performed the following steps.
(1) He took a leaf and boiled it in water.
(2) He placed the leaf in a petri dish and poured some iodine over it. He did not get the expected result. Which step did he miss? Explain.

Open in App

Solution

Experiment to prove the presence of starch in leaves:
Boohji's experiment did not provide the desired results because he skipped a key phase in the protocol.
Take a leaf and boil it in water.
To get rid of the chlorophyll, boil the leaf in booze or spirit.
The leaf should be put in a petri dish with some iodine added.
To remove the chlorophyll (green color pigment) from the leaf, he did not boil it in alcohol or spirit.
Chlorophyll must be eliminated since it tampered with the starch test.
Only the decolorized leaf turns blue-black when iodine is added, indicating that starch is present as shown below:

Suggest Corrections

Similar questions

A candidate studied the importance of certain factors in photosynthesis. He took a potted plant and kept it in the dark for over 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) Is there any control in this experiment ? If so, state it.

(d) Describe step by step, how the candidate proceeded to test leaf for the presence of starch.

Q. In an experiment to test the presence of starch in a leaf, the plucked leaf is first boiled in water for a few minutes. This is an important step in the experiment because it :
(1) converts glucose made in the leaf into starch
(2) dissolves chlorophyll present in the green leaf
(3) extracts starch to destarch the leaf
(4) makes the leaf more permeable to iodine solution

Q. In an experiment to test the presence of starch in a leaf, the leaf is boiled in alcohol for a few minutes using a water bath. This is an essential step in the experiment because alcohol:
(1) softens the leaf
(2) disinfects the leaf
(3) allows iodine to enter the leaf
(4) dissolves chlorophyll from leaf

Q. Arun carried out the following experiment with a croton (variegated) leaf. He drew the leaf in his notebook marking the green and the non-green area. He put the leaf in hot alcohol till all the green colour came out and the leaf turned white. He then washed the leaf in water and covered the leaf in iodine solution.
(a) Why did he draw the leaf and mark the green and non-green areas?
(b) What was the colour change in iodine solution?
(c) Which portions of the leaf show colour change?
(d) what can you conclude from this experiment?

To test a leaf for starch, the leaf is boiled in water to (i) ____________.

It is then boiled in Methylated spirit to (ii) ___________.

The leaf is dipped in warm water to soften it. It is places in a petri dish, and (iii) __________ solution is added.

The region of the leaf which contains starch, turns (iv) _________ and the region which does not contain starch turns (v) ___________.

Join BYJU'S Learning Program

Boojho wanted to test the presence of starch in leaves. He performed the following steps. (1) He took a leaf and boiled it in water. (2) He placed the leaf in a petri dish and poured some iodine over it. He did not get the expected result. Which step did he miss? Explain.

Boojho wanted to test the presence of starch in leaves. He performed the following steps.
(1) He took a leaf and boiled it in water.
(2) He placed the leaf in a petri dish and poured some iodine over it. He did not get the expected result. Which step did he miss? Explain.