First boil the leaf in water then transfer this leaf into a test tube containing methylated spirit. Boil this tube in a water bath. Chlorophyll dissolves in spirit and the leaf becomes pale, due to removal of chlorophyll.

Take the leaf carefully from test tube by using a brush. Spread the leaf in a petridish and add a few drops of iodine/ betadine solution on it. Observe the leaf.

What do you see/notice?

The presence of starch will be indicated by a blue-black colour. Do you think solar energy transforms into chemical energy by the process of photosynthesis?

Factors (Materials) essential for the process of Photosynthesis

What are the materials that you think would be essential for the synthesis of carbohydrates in the process of photosynthesis?

(Hint: see the equation proposed by Van Neil)
Do you think the equation tells us about all the materials involved? It took scientists over 300 years to find out about them. They opined that we don’t know about several materials involved in the process still.

Let us study how scientists experimented to find out about some of the materials required for the process of photosynthesis.

Water and Photosynthesis

In class VII we already studied how Von Helmont found that the water is essential for the increase of plant mass.

He did not know about photosynthesis then. Later, it was found that increase in plant body mass or material occurred due to the process of photosynthesis.

We shall study more about it in the following sections. Read the chapter on ‘Nutrition in Plants’ in class VII. Discuss with your friends and write a note on Von Helmont’s experiment focussing on how he concluded that water was important for plant growth and increase in body mass.

Air and Photosynthesis

Let us discuss an experiment on photosynthesis. This one helps us to find out about the role of air in the process of photosynthesis. It is interesting to learn about the experiment which is one of the several milestones in the gradual development of our understanding of Photosynthesis.

Joseph Priestly (1733-1804) in 1770 performed a series of experiments that revealed the essential role of air on the growth of green plants