(WI
26. The diagram below illustrates iodine test for the
presence of starch in a leaf.
(a) Why is the leaf boiled in water for few minutes ?
(b) Why will the colour of leaf after boiling it with
methylated spirit turns pale white ?
(c) Why is the leaf again boiled in hot water ?
(a) What is the composition of iodine solution in
100 mL of water ?
Answers
Answer:
(a) Why is the leaf boiled in water for few minutes ?
(b) Why will the colour of leaf after boiling it with
methylated spirit turns pale white ?
(c) Why is the leaf again boiled in hot water ?
(a) What is the composition of iodine solution in
100 mL of water ?
Answer:
a)Boiling the leaf in alcohol removes chlorophyll present in it. By this we can properly identify the starch present in the leaf
b)Why will the colour of leaf after boiling it with methylated spirit turns pale white? Methylated spirit removes the chorophyll from leaf and make it pale white from green.
c)This procedure kills a leaf, disrupts the cell membranes and softens the cuticle and cell walls. This makes it possible to extract the chlorophyll with hot ethanol and also allows the iodine solution to penetrate the cells and react with any starch present.
d)This 100 ml bottle is an aqueous solution of 1.8% iodine and 3.0% potassium iodide. This iodine solution is water-based.
...
Iodine (Lugol's) Biological Stain Solution, 100 ml.
Formula I3K
Common Use Testing for starch