In 1933, scientist Lundigaard and his colleague Bersatrum introduced the theory about the absorption of mineral salts by plants called Lundigaard’s theory. According to this theory, cytochromes play an important role in the absorption of iron minerals, so it is also called the cytochrome pump theory. They observed that placing the plant in a solution of salt from water increased the respiration rate of the plant. They termed this increased respiration as anion-respiration or salt-respiration.
According to Lundigaard’s cytochrome pump theory, every cell has two compartments. Outer floor and inner floor. Protons (H+) and electrons (e+) are produced in the dehydrogenase reaction inside the cell. Protons (H+) move directly to the outer layer of the cell and combine with oxygen to form water (H2O). On the other hand, electrons (e+) enter the cytochrome chain. Inside the cell, cytochromes are oxidized by accepting electrons. After entering the cytochrome chain, electrons (e+) cycle to the outside of the cell. On the outer surface of the cell, cytochromes are oxidized by releasing electrons. Oxidized cytochrome combines with the anion (A-) located in the cell membrane to form a ‘cytochrome-anion’ compound. The anion (A-) cycles through the cytochrome chain to the intracellular surface and accumulates. An excess of anions (A-) on the inside of the cell causes an electrical-potential difference. To equalize this electric-potential difference, cations (K+) from the outer surface of the cell move directly into the inner surface of the cell. Later, cations and anions combine to meet the cell’s mineral salt needs.
Fe++ (2A-) – e- + A- → Fe+++ (3A-)