“Absorption Theory Involved In Nutrient Uptake and its Physiology and its Importance”.

1. Topic
on
Department of Plant Physiology
“Absorption Theory Involved In Nutrient Uptake and its
Physiology and its Importance”

2. Uptake of nutrients :-
• An Active process.
• Nutrient uptake is the mechanism by which plants capture all those
elements that are essential for their growth.
• Plant uptake is water taken from the groundwater flow and soil
moisture.
• Only 1% of water the plant draws up is used by the plant.

3. CONT..

4. Absorption theory involved in nutrient uptake
• Passive Absorption:
• Absorption of ions without the use of metabolic energy is known
as passive absorption.
• This type of absorption is carried out by purely physical forces.

6. 1. Mass Flow:-
• The pressure flow hypothesis, also known as the mass flow hypothesis.
• It is the best-supported theory to explain the movement of sap through the
phloem.
• Movement of phloem sap occurs by bulk flow (mass flow) from sugar sources
to sugar sinks.

7. 2. Ion-Exchange
• It is process of mineral absorption, the ions adsorbed on the surface of the
root can exchange with the ions of the same charge from the soil solution.

8. cont…
1. Contact Exchange Theory:-
 According to this theory, the ions adsorbed on the surface of root cells and
clay particles (or clay micelles) are not held tightly but oscillate within
small volume of space.
2. Carbonic Acid Exchange Theory:-
 According to this theory, the CO2 released during respiration of root cells
combines with water to form carbonic acid (H2CO3).

9.  Donnan equilibrium describes the equilibrium that exists between
two solutions that are separated by a membrane.
 The membrane, however, does not allow the passage of all the ions
present in the solutions and is thus a selectively permeable
membrane.
3. Donnan Equilibrium :-

10. • Active Absorption :-
 Absorption of ions with the use of metabolic energy is known
as active absorption.
 Absorption of water by roots with the help of adenosine
triphosphate, generated by the root respiration as the root cells
actively take part in the process.

12. .
A) Carrier Concept:
• According to this theory the plasma membrane is impermeable to free ions.
But some compound present in it acts as carrier and combines with ions to
form carrier-ion-complex which can move across the membrane.
• On the inner surface of the membrane this complex breaks releasing ions
into the cell while the carrier goes back to the outer surface to pick up fresh
ions.

13. 1) Bennet-Clark’s Protein-Lecithin Theory:
• In 1856, Bennet – Clark suggested that because the cell membranes
chiefly consist of phospholipids and proteins and certain enzymes seem
to be located on them, the carrier could be a protein associated with the
phosphatide called as lecithin.

14. B) Cytochrome Pump Theory
 Lundegardh and Burstrom (1933) believed that there was a definite
correlation between respiration and anion absorption.
 Cytochrome pump theory which is based on the following
assumptions:
1. The mechanism of anion and cation absorption is different.
2. Anions are absorbed through cytochrome chain by an active process.
3. Cations are absorbed passively.

15. IMPORTANCE:
 Active transport is important because it allows the cell to move substances against the
concentration gradient.
 Passive transport substances simply move from an area of higher concentration to an area
of lower concentration, which does not require the input of energy.
 Mass flow is the movement of dissolved nutrients into a plant as the plant absorbs water for
transpiration. This is important for the transport of phosphorus and potassium.
 Ion exchange resins are useful for the removal of water problems including hard water,
scale buildup, nitrates, arsenic and more.
 Donnan membrane equilibrium has important applications in colloid chemistry and in the
technologies of leather and gelatin, but above all in the understanding of the living cell,
where it can give a quantitative account of ionic equilibria both within the cell and between
the cell and its environment.
 Carrier proteins "carry" the ion or molecule across the membrane by changing shape after
the binding of the ion or molecule.
 Importance of transpiration and the role of chlorophyll in plants.
 Cytochrome pump theory, the anion is absorbed through an active process whereas cation
is absorbed through a passive process.

16. .
• Related Articles:
 Absorption of Solute by Plants | Botany.
 Absorption of Mineral Salts by Higher Plant (With
Diagram).