Vital theory
Encyclopedia
"Vital force theory" is a proposed mechanism for the ascent of sap through the xylem
tissue of plants.
According to the vital force theory, the conduction of water up the xylem
vessel is a result of vital action of the living cells
in the xylem tissue.
Jagadish Chandra Bose suggested a mechanism for the ascent of sap
in 1927. He found electrical ‘pulsations’ or oscillations in electric potentials, and came to believe these were coupled with rhythmic movements in the telegraph plant Codariocalyx motorius
(then Desmodium
). On the basis of this Bose theorized that regular wave-like ‘pulsations’ in cell electric potential
and turgor pressure
were an endogenous
form of cell
signaling. According to him the living cells in the inner lining of the xylem tissue pump water by contractive and expulsive movements similar to the animal heart
circulating blood.
This mechanism has not been well supported, and in spite of some ongoing debate, the evidence overwhelmingly supports the cohesion-tension theory for the ascent of sap.
Xylem
Xylem is one of the two types of transport tissue in vascular plants. . The word xylem is derived from the Classical Greek word ξυλον , meaning "wood"; the best-known xylem tissue is wood, though it is found throughout the plant...
tissue of plants.
According to the vital force theory, the conduction of water up the xylem
Xylem
Xylem is one of the two types of transport tissue in vascular plants. . The word xylem is derived from the Classical Greek word ξυλον , meaning "wood"; the best-known xylem tissue is wood, though it is found throughout the plant...
vessel is a result of vital action of the living cells
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....
in the xylem tissue.
Jagadish Chandra Bose suggested a mechanism for the ascent of sap
Ascent of sap
The ascent of sap in the xylem tissue of plants is the upward movement of water from the root to the crown. Xylem is a complex tissue consisting of living and non-living cells. The conducting cells in xylem are typically non-living and include, in various groups of plants, vessels members and...
in 1927. He found electrical ‘pulsations’ or oscillations in electric potentials, and came to believe these were coupled with rhythmic movements in the telegraph plant Codariocalyx motorius
Codariocalyx motorius
Codariocalyx motorius , known as the Telegraph Plant or Semaphore Plant, is a tropical Asian shrub, one of a few plants capable of rapid movement; others include Mimosa pudica and the Venus Flytrap....
(then Desmodium
Desmodium
Desmodium is a genus in the flowering plant family Fabaceae, sometimes called tick-trefoil, tick clover or beggar lice. There are dozens of species and the delimitation of the genus has shifted much over time....
). On the basis of this Bose theorized that regular wave-like ‘pulsations’ in cell electric potential
Electric potential
In classical electromagnetism, the electric potential at a point within a defined space is equal to the electric potential energy at that location divided by the charge there...
and turgor pressure
Turgor pressure
Turgor Pressure or turgidity is the main pressure of the cell contents against the cell wall in plant cells and bacteria cells, determined by the water content of the vacuole, resulting from osmotic pressure, i.e...
were an endogenous
Endogenous
Endogenous substances are those that originate from within an organism, tissue, or cell. Endogenous retroviruses are caused by ancient infections of germ cells in humans, mammals and other vertebrates...
form of cell
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....
signaling. According to him the living cells in the inner lining of the xylem tissue pump water by contractive and expulsive movements similar to the animal heart
Heart
The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...
circulating blood.
This mechanism has not been well supported, and in spite of some ongoing debate, the evidence overwhelmingly supports the cohesion-tension theory for the ascent of sap.