Question

Vital theories of ascent of sap were discarded due to reasons that

• A. Living cells are involved.
• B. Metabolic activity provides energy requirements.
• C. Water continues rising even after killing of xylem parenchyma.
• D. Atmospheric pressure is involved in ascent of sap.

Answer 1

The correct option is C Water continues rising even after killing of xylem parenchyma.

Vital force theories were propagated to explain the ascent of sap. These theories believed that living cells are involved in the ascent of sap e.g., relay pump theory by Godlewski, 1883 and pulsation theory by Bose, 1923. Bose believed that the inner most cortical cells pump water into the interior, that contains xylem channels. The vital force theories have been discarded because as proved by Boucherie in 1840 and Strasburger in 1891 that water rises up the stem, even when all the living cells are killed by poison or heat.