Page 2 - LN-PHOTOSYNTHESIS IN PLANTS

48 hours).
After fixing paper, the set-up is exposed to sunlight for 2-6 hrs. After removing paper,
the test for starch is performed over leaf. Starch is produced only in area that
received light, shows that light is necessary for photosynthesis.
Necessity of Water
Through radio labelling of oxygen in water molecule, it is confirmed that the 02
released during photosynthesis comes from H 2O, not CO 2.
Early Experiments
Study of photosynthesis started about hundreds of years ago. Prior to that
researchers used to believe that plants gets all of their nourishment from soil only by
the means of roots. Thus, several simple experiments led to the development of
understanding of the process involved. Some early experiments performed by
different scholars are as follows.
Joseph Priestley
He performed a series of experiments in 1770s that revealed about the essentiality
of air in the growth of green plants. He observed that a burning candle or a respiring
mouse in a closed space, (i. e., bell jar) soon gets extinguished and died due to
suffocation respectively, because burning candle and animal that breathe the air
soon get damages.
On the other hand after placing a mint plant in the bell jar along the burning candle
and mouse, he observed that the mouse stayed alive and also the candle continue to
burn for a longer time.

Conclusion
Priestley hypothesized that the foul air produced by the burning of candles and
mouse respiration could be converted into pure air by plant (mint plant in this case).
Jan Ingenhousz (1730-1799)
He performed his experiments by using same set-up used by Priesdey. In his
experiment with an aquatic plant, he showed that in bright sunlight, formation of
small bubbles take place around the green parts, while in the dark, formation of