Question

Relay pump theory of ascent of sap was proposed by
A. Bose
B. Godlewski
C. Westermaler
D. Von Sachs

Answer 1

Relay pump theory is one of the vital- force theories which describes how the vital capacity of living cells (xylem parenchyma and ray cells) are responsible for the ascent of sap. Relay force theory also called Clambering theory which explains translocation of water and dissolved minerals from roots to the crown part of plants.

Complete step by step answer: Relay pump theory describes upward movement of water and mineral salts in dissolved form. This movement occurs from roots to leaves and other parts in xylem tissue of plants and this process of pumping action of water in upward direction is known as the ascent of sap. Transpiration process helps to pull sap upwards as evaporation causes a deficit of water in the leaf due to which water is pulled in upward direction. Ascent of sap occurs through xylem due to rhythmic change in osmotic pressure of living cells of xylem parenchyma and medullary rays. Xylem is complex tissue which has tracheids, vessels and parenchyma which is only a living cell. Xylem tissues cause pumping action to facilitate the movement of water in a vertical direction against gravity. When water potential decreases of living cells it diffuses water from adjacent bordering vessels used as reservoir for water and mineral storage. This whole theory of movement of water was explained by Godlewski in 1884.
Thus option B is the correct answer- Godlewski.

Note: Godlewski’s Relay pump theory was opposed by strasburger which showed the continuous movement of water in plants even after dying of living cells in plants by his experiment. This theory is responsible for bringing pumping action of water in an upward direction.