Tag: botany

The ascent of sap is the mechanism by which water moves from the roots to the top of the trees. Studies on the process of an ascent of sap show that the strong cohesive force between the water molecules (cohesion), the attraction between water molecules and the wall of the xylem elements (adhesion) and the transpiration pull creates a tension on the water column, which ensures continuity of water column in plants. The water lost from the leaves during transpiration creates a high solute potential and reduces water potential. The reduced water potential creates a suction pull and allows ascent of sap. 

The transpiration pull theory is the most accepted theory for the ascent of sap. Dixon and Jolly gave transpiration pull theory. According to this theory, the ascent of sap in plants is a passive physical process, which occurs under the influence of transpiration pull generated due to loss of water from aerial parts. The water lost from the leaves creates a high solute potential and reduces water potential. The reduced water potential creates a suction pull and allows ascent of sap. Other than the pull, a continuous column of water is also essential for the rise of water in xylem elements. The continuous column of water is maintained by cohesion forces between water molecules and adhesive forces between water molecules and vascular elements of the plant.

The movement of water in the plants is known as the ascent of the sap. This upward movement is due to the pulsatory activity of the living cell. This theory was supported by J. C. Bose. he explained that there is rhythmic form of pulse-like movement which helps the water to be transported in the upward direction. 

There are several vital theories which help in understanding the concept of the conduction of water by xylem. Westermaier explained the theory that the upward conduction of water is due to xylem parenchyma cells. The tracheids and the vessels act as water reservoirs. This allows the movement of the water in upward direction. 

Tap root is a type of roots which has a major big central root and small branching. These go very deep in the soil and are very strong.

• Down to upwards movement is known as ascent and Top to downwards movement is known as descend.
• In plants sap is water and minerals.
• Ascent of sap in the xylem tissue of plants is the upward movement of water and minerals from the root to the top. 
  

This experiment was introduced by Malpighi in 1675. It involves the removal of a ring of bark (girdle), that is, all tissues outside the vascular cambium. Thus, the correct answer is (B).

When any material movement is from down to upwards it is called as ascending movement.