Lundegandh's Cytochrome Pump Theory-
Lundegardh and Burstrom (1933) observed a correlation between respiration and anion absorption. When a plant is transferred from water to a salt solution the rate of respiration increases which is called as anion respiration or salt respiration. Based on this observation Lundegarth (1950 and 1954) proposed cytochrome pump theory which is based on the following assumptions:
i. The mechanism of anion and cation absorption are different
ii. Anions are absorbed through cytochrome chain by an active process, cations are absorbed passively
iii. An oxygen gradient responsible for oxidation at the cuter surface of the membrane and reduction at the inner surface.
According to this theory, the enzyme dehydrogenase on inner surface is responsible for the formation of protors (`H^(+)`) and electrons (`e^(-)`). As electrons pass outward through electron transport chain there is a corresponding inward passage of anions. Anions are picked up by oxidized cytochrome oxidase and are transferred to other members of chain as they transfer the electron to the next component.
The theory assumes that cations (`C^(+)`) move passively along the electrical gradient created by the accumulation of anions (`A^(-)`) at the inner surface of the membrane.
Main defects of the above theory are:
(i) Cations also induce respiration.
(ii) Fails to explain the selective uptake of ions.
(iii) It explains absorption of anions only.
