Take a potted plant with destarched leaves.

Remember the process of destraching leaves mentioned in activity-1.

Cover one of its leaves with black paper on which a design is cut. Fix the paper on the leaf in such a manner that light does not enter the dark part.

Place this potted plant in sun light.

After few hours of exposure to bright sunlight, test the leaf which is covered by black paper for the presence of starch.

Which part of the leaf turns blue black? What about the remaining part?

Observe the colour of leaf stained with iodine. Can you tell why it is stained differently?

It will be observed that only the parts of the leaf, which could get light through the cut out design, turns blue-black showing the presence of starch.

Chlorophyll and Photosynthesis Ingenhousz wanted to find out more about photosynthesis and carried out several other experiments. He proposed that only green plant parts could carry out the process of photosynthesis.

What about plants having coloured leaves? How is it that new leaves which look dark red in colour in several plants turn green?

Do plants having reddish or yellowish leaves also carry out photosynthesis?

What made plants carry out photosynthesis while even green coloured animals (like some birds )could not?

Questions like these remained challenges until scientists could isolate the green coloured substance from plant parts and study its nature.