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This is a "pulling theory." Water vapor is released out of the leaf's stomata . Water behind it replaces the water lost. Water molecules "stick together" by cohesive forces (cohesian tension) , thus a column of water rises up the xylem tissue of the stem.

The movement of sap (primarily downward) is an entirely different mechanism.

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Do transpiration have no effect over ascent of sap?

Transpiration creates a negative pressure that helps pull water upward in the xylem vessels, playing a major role in the ascent of sap in plants. As water evaporates from the leaf surface during transpiration, it creates tension that helps to draw water molecules up from the roots. This process, known as the cohesion-tension theory, is essential for the movement of water and nutrients throughout the plant.


What two forces drive the flow of water from the roots to the leaves?

transpiration and ascent of sap


What meant by the ascent of xylem water?

Ascent of xylem water is also known as the ascent of sap as sap contains minerals dissolved in water. Ascent of sap is actually the movement of sap from the roots all the way to the leaves where it can be utilized in photosynthesis. There are two prposed theories so as to exlain the ascent of sap. One is the "Root Pressure Theory" which says that root exerts a pressure on the water to push it upwards by absorbing more from the soil. But this pressure works only for a few metres. The second theory is more acceptable; "The transpiration Pull". According to this one, when water is transpired through the leaves, the evaporating water molecules pull the ones after them with the help of the adhesive and cohesive forces. This helps in the ascent of water from the roots, all the way through the xylem, to the leaves.


What is the rate of ascent of sap?

Plant sap and tree sap originate in the roots and then climb to nourish the leaves. We take advantage of this ascension in maple trees. When their sap begins to ascend in the Spring, we tap the trees and collect and boil the sap in the production of maple syrup. Vet59Man


Does the stoma open of shut in the light?

in day light , they are open, and perform the following three functions 1 Transpiration 2 Gaseous exchange 3 Promotion of ascent of sap***


Who discovered ascent of sap?

I have no fricken idea!


What takes water and minerals from the root to the shoot?

Xylem tissue by ascent of sap


What is the difference between plant in sun with water and the plant in dark without water?

When the plant is placed in sunlight having sufficient water to absorb, it undergoes rapid transpiration and upward movement of water (ascent of sap). This phenomenon is slowed down in dark without water.


What is the process called when roots supply water to the tree?

Osmotic absorption of water by root hairs and ascent of sap.


What will happen to plants if there is no transpiration?

A plant can not have no stomata, some plants such as cacti have very little but still have some. Hypothetically if a plant had none it would die because plants need their stomata to take carbon dioxide in and let oxygen out.


Describe the path taken by water at the moment it enters the leaf and leaves through the stomata?

Water enters the leaf through the roots and moves up through the stem to the leaves via the xylem vessels. Once in the leaf, water moves through the mesophyll cells and eventually evaporates from the stomata as water vapor during transpiration.


Does the stoma open or shut in the light?

OpenIn day light , they are open, and perform the following three functions1. Transpiration2. Gaseous exchange3. Promotion of ascent of sap