Jagdish Chandra Bose (1923) an eminent physicist and a plant physiologist strongly supported the vital theory of ascent of sap. He was of the opinion that the innermost layer of cortical cells abutting the endodermis are of a special category as they are endodwed with rhythmic pulsa­tions, which is electrical in na­ture.

These cells are responsible for the pumping up of water into the xylem. Bose’s theory, called pul­sation theory en­visages that the al­ternating contrac­tion and expansion of these cells forces water into the xylem. In or­der to prove the electrical pulsa­tion of the inner­most cortical cells, Bose invented an instrument called the cresograph, which consisted of an electric probe was attached to a galvanometre.

When the fine needle of the probe was pierced into the cor­tex there were minor oscillations. When the probe reached the inner cortical cells however, the oscillations in the galvanometre indicator became violent and continuous. This showed the high electrical activity of the inner cortical cells. Bose believed that these cells expand when they absorbed water from the outer cortical cells and after pushing water into the xylem they contacted. Each contraction and expansion took 14 secs to several minutes.

Shull, MacDougal and others have shown that the pulsatory activity of the inner cortical cells has no relation to ascent of sap. Further, in order to account for the rate of ascent of sap, the pulsation rate must be far higher than what is demonstrated by Bose. Benedict (1927) showed that the rate of as­cent of water is 8,000-30,000 times higher than the pulsation rate recorded by Bose.