In ascent of sap, the biggest challenge is the force required to lift the water to the top of the tallest trees. A number of theories have been put forward to explain the mechanism of ascent of sap as follows. Mechanism of transportation of water in plants. A number of theories have been put forward from time to time to account for the ascent of sap. Various theories have been put forward by different scientists to explain the process of ascent of sap. Vital force theories, B. Root pressure theory, and C. Physical force theory. Vital Force Theories The hydrostatic pressure generated in the root which forces the water upward in the stem is called root pressure. The ascent of sap takes place in the lumen of vessels and tracheids situated between the parenchyma root hair and cortex of the root below, and the mesophyll tissue of the leaf above. THEORIES EXPLAINING ASCENT OF SAP. Root pressure forces the water up from below. Root pressure theory 3. Root pressure theory. The conducting cells in xylem are typically non-living and include, in various groups of plants, vessels members and tracheids. They are as follows: Vital theories. Vital theories: Westermaier in the year 1883 for the first time suggested that living cells take part in ascent of sap. Mechanism of ascent of sap. Mechanism of ascent of sap. Theories of ascent of sap : The various theories put forward to explain the mechanism of ascent of sap in plants can be placed in following three categories : (1) Vital force theories Mechanism of Ascent of Sap . Here are following theories which explain the ascent of sap in plants: a) Root pressure (b) Capillarity (c) Vital theory and (d) Cohesion-tension theory. 1. 1. The ascent of sap in the xylem tissue of plants is the upward movement of water and minerals from the root to the crown. Typical red wood tree: About 350 ft. (a) ROOT PRESSURE. 1. Here are following theories which explain the ascent of sap in plants: a) Root pressure (b) Capillarity (c) Vital theory and (d) Cohesion-tension theory. Ascent of sap involves root pressure and transpiration pull. mechanism of ascent of sap 1. Root pressure forces the water up from below. Although a mechanism of ascent of sap is not well understood, a number of theories have been put forward to explain it. Australian Eucalyptus: About 450 ft. Vital theories. Various theories based upon biological and physical phenomena were suggested to explain the mechanism of rapid translocation of water from roots to the uppermost leaves. They are, A. It is dilute solution of mineral ions absorbed from the soils. According these theories, the living cells of the plants are responsible for the ascent of sap… Many theories have been proposed to explain the mechanism of ascent of sap. (a) ROOT PRESSURE The hydrostatic pressure generated in the root which forces the water upward in the stem is called root pressure. This water is conducted upwards to the leaves through xylem. But, the most widely accepted theory is Dixon’s theory of ascent of sap. Vital theories. Vital theories 2. According to this theory the water present in the leaves is continuously evaporated by sunlight falling over them. Further, it has been proved experimentally that sap moves up the stem through the lumen of xylem vessels and tracheids and not through their walls. Physical force theories . 2. Explain mechanism of ascent sap - 2433421 Hey, friend, The fluid that moves upward in the stem is not pure water. Xylem is a complex tissue consisting of living and non-living cells. Physical theories. Live pump theories: Plant physiologists of 1880’s like Westermeir, Godlewski, Sir J. C. 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