Question

How would you test the precense of startch in leaves

Answer 1

Explanation:

To test the presence of Starch in Leaves,

We need to do a activity.

• Activity 1

Materials Required

• A sapling pot
• A black PVC tape
• Iodine Solution
• Dropper

Procedure

1. First take any leaf of the sapling of the plant and cover it in black tape
2. Now, take the plant and keep it in sunlight & provide necessary water and space as required in the sun.
3. Now, open the tape after few days.
4. Put some Iodine solution on the leaf.

Observation

• We see that the space where we put the black tape is blank and the space which was under normal conditions turns blue black in color.
• Also it shows that Sunlight is essential for photosynthesis

Activity 2.

Materials

• A sapling pot where there are fresh sprouted leaves
• A container.
• Iodine solution

Process

1. Take a container and put some water and start boiling it.
2. Put a fresh leaf in it
3. Take another leaf from the plant.
4. Put Iodine solution in it.

Observation

• The boiled leaf has dead cells and hence no starch is formed in it
• The fresh leaf turns blue black in color.

These both activities show that there is presence of Starch in leaves.

Answer 2

Explanation:

Experiment to Show the presence of starch in leaves :-

Step 1 :-

At first take a potted plant having long and narrow leaves

Step 2 :-

Take a thin strip of aluminum foil and wrap it in the centre of one leaf on both the sides

Step 3 :-

Keep the potted plant in bright sunshine for 3-4 days

Step 4 :-

Pluck the partially covered leaf from the plant and remove its aluminium foil. Immerse the leaf in boiling water for a few minutes.

Step 5 :-

Put the plucked leaf in beaker containing alcohol. Place the beaker containing alcohol and leaf in a water bath.

Note :-

A water bath is being used here for heating alcohol because alcohol is highly inflammable liquid. So, if alcohol is heated directly over a flame, then it will catch fire at once.

Step 6 :-

Boil the green leaf in alcohol till all its green pigment (chlorophyll) is removed. After boiling the leaf become almost colourless

Step 7 :-

Remove the colourless leaf from alcohol and wash it throughly with hot water.

Step 8 :-

Drop iodine solution over the decolourised leaf with the help of a dropper.

Step 9 :-

We see that, the middle part of the leaf which was covered with aluminum foil doesn't turn blue-black on adding iodine solution because no starch is present in this middle part of the leaf.

Step 10 :-

The uncovered part of leaf which was exposed turns blue-black on adding iodine solution showing that starch is present in this part of the leaf. This means that the part of leaf which was exposed to sunlight could do photosynthesis to make starch.

Step 11 :-

Since, the part of leaf which was covered and hidden from sunlight doesn't contain starch.

Conclusion :-

• Sunlight is necessary for the process of photosynthesis.
• leaves make starch as food by photosynthesis.