Question

As per Cornelius Van Niel, where did O₂ evolve from in green plants?

Answer 1

Evolution of oxygen in green plants:

1. Water and carbon dioxide are taken up by plants from soil and air is oxidized and reduced to oxygen and glucose, respectively.
2. Oxidation is losing electrons, whereas reduction is when electrons are gained.

Cornelius Van Biel experiment:

1. He was the first scientist who demonstrated that photosynthesis is a light-dependent reaction in which hydrogen (from an oxidizable compound) reduces CO₂ to carbon compounds or sugar.
2. He conducted an experiment using green and purple sulphur bacteria.
3. In this setup, he used sulphur hydroxide (instead of water) as a hydrogen donor.
4. He observed that there was no formation of oxygen (as expected in photosynthesis).
5. Therefore, he concluded that O₂ evolved from water.
6. He also inferred that an oxidation-reduction process, with the action of hydrogen in water, gives carbon compounds.

$$\begin{gathered} 2H_{2}A+C{O}_2\to 2A+C{H}_{2}O+H_{2}O \\ A-electronacceptor \end{gathered}$$