Best vital force theory was proposed by
A. Godlewski
B. Strasburger
C. Dixon
D. Esau

Hint: For the upward transport of water through xylem, many theories were given. Some scientists considered that vital forces are responsible for this. Some scientists considered that physical forces are responsible for the ascent of sap.

Complete step-by-step answer: In relay pump theory it was told that in stem water movement by two forces that are atmospheric pressure and periodic changes in osmotic pressure of medullary rays.
Xylem parenchyma cells absorb water from xylem vessels. This absorbed water moves upside due to the atmospheric pressure. In xylem vessels that are present upon these xylem vessels osmotic pressure is decreased, so the water present in parenchymatous cells absorbed by these vessels.
This process is repeated again and again and water moves upside in vessels.
The classical vital theories attempted to explain the mechanism of ascent of sap. These classical theories have not been accepted much. Most important vital theories were 'Relay pump theory' given by Godlewski.
The concepts related to vital forces were not accepted because for movement of water upside only physical forces are responsible. Other theories for vital forces were also given by Wastermaier, Jansey and J. C. boss.


So, the correct answer is “Option A. Godlewski”.

Note: The concepts related to vital forces were not accepted because for movement of water upside only physical forces are responsible. Other theories for vital forces were also given by Wastermaier, Jansey and J. C. boss.