The supporters of this theory said that the upward movement of water occurs not due to living cells or root pressure but it occurs due to other physical phenomenon. Few important theories are as follows :
a) Capillary force theory :
This theory is given by Boehem. According to this theory, the upward movement of water occurs due to capillary force which is created by Xylem tube. This theory is also discarded due to following reasons:
I) Xylem tube is not like capillary tube because development of xylem is different in winter and summer season.
ii) Capillary tube works only in free surface of water. But in plant body, there is no free surface of water.
iii) The capillary tube has very small diameter which can raise water only upto 150 cm but most of the plant height is more than this.
b) Transpiration pulls or Cohesive theory:
This theory is purposed by Dixon and Jolly in 1894. and later supported by many scientists in 1950, 1952, 1960. According to this theory, the upward movement of water occurs due to transpiration pull which creates cohesive and adhesive force in plant body. The force of attraction between two similar molecules is called cohesive force and force of attraction between two dissimilar molecules is called adhesive force. Cohesive force develops in water molecules and adhesive force develops in water molecules and with xylem tube. Due to transpiration pull, cohesive and adhesive force develops upto 350 cm by which water can be easily raised upto very higher then present-day tallest trees. This theory is one of the best theories of ascent of sap.